bluuebunny/crossref_metadata_2025 huggingface dataset:
A majority of Ig H chain cDNA of normal human adult blood lymphocytes resembles cDNA for fetal Ig and natural autoantibodies.
Authors: Huang C , Stollar B D
Published: December 2022

Certain Ig VH gene segments, with few or no mutations, recur frequently in natural autoantibodies, fetal antibodies, and products of B cell tumors. The goal of this study was to determine whether similar Ig gene segment usage occurs in normal human adult PBL. Extending previous analyses, 105 randomly picked H chain V region clones of representative cDNA libraries from PBL were sequenced. Clones were from: IgM and IgG libraries from one RNA sample of a normal adult; a second IgM library from the same subject 11 mo later; and one IgM library from a second subject. Although some clones had clear evidence of mutation, 48 of 77 IgM clones (62%) shared 99% or more identity with known germline VH segments, and most of these had no mutations in the CDR3 portion of the JH segment. Certain VH gene segments, expressed in autoantibodies and fetal antibodies, occurred at high frequency in these libraries. Fourteen of the clones with 99% identity to known VH segments had CDR3 segments identical to portions of known germline DH gene sequences; two such clones had no N nucleotides at the VHDH or DHJH junctions. IgG-encoding sequences had more mutations than IgM-encoding sequences. JH and DH usage was not random. The circulating B cell population may represent a distinct compartment, with a large proportion of cells similar to those of the fetal and natural autoantibody repertoire. Polyreactive Ig products of these circulating cells may serve a screening function, binding and delivering diverse Ag to secondary lymphoid tissues where more highly selective antibodies are formed to foreign or self-Ag.
Isolation of a classical MHC class I cDNA from an amphibian. Evidence for only one class I locus in the Xenopus MHC.
Authors: Shum B P , Avila D , Du Pasquier L , Kasahara M , Flajnik M F
Published: December 2022

The amphibian Xenopus is an ectothermic vertebrate in which the MHC has been studied extensively at the functional, biochemical, and genetic levels. A cDNA clone corresponding to the MHC class la gene (Xela-UAA1f) of Xenopus laevis was isolated by screening a cDNA phage library with oligonucleotides based on NH2-terminal protein sequence. Three pieces of evidence support its status as a class la gene: 1) Previous biochemical data suggested that only one polymorphic class la molecule is expressed per MHC haplotype in X. laevis. NH2-terminal sequencing of the class I protein encoded by the f haplotype showed a single unambiguous sequence of the first 22 amino acids; the deduced protein sequence of the cDNA clone matches precisely to this peptide sequence; 2) Genes that hybridized to the cDNA clone segregated perfectly with the serologically typed MHC in two family studies; and 3) There is a strong conservation of amino acids in the peptide-binding region that have been shown in mammals to dock peptides at their NH2- and COOH-termini. In contrast to all other species that have been examined, there appears to be only one class I locus present in the MHC of X. laevis. Xenopus speciates by allopolyploidization, and there are Xenopus species with different levels of ploidy (2n-12n). Functionally, the MHC has been shown to be "diploidized" in most Xenopus species. As in previous studies with MHC class II and HSP70 probes, there is a trend toward maintaining a diploid number of class la genes in all Xenopus species regardless of their chromosome number, probably accomplished through a deletional mechanism. Thus, there is a strong pressure in Xenopus to maintain very few MHC-linked class I genes, exemplified both by the number of class I genes per MHC haplotype and by the number of class la genes per organism.
IL-10 neutralization augments mouse resistance to systemic Mycobacterium avium infections.
Authors: Denis M , Ghadirian E
Published: December 2022

In this contribution, we examined the involvement of the cytokine IL-10 in the progression of experimental murine Mycobacterium avium infections in susceptible BALB/c mice. Addition of anti-IL-10 antibodies in the supernatants of peritoneal macrophages infected with virulent M. avium resulted in a significantly enhanced mycobacteriostatic activity of macrophages. In BALB/c mice infected with the B101 or B102 virulent M. avium strains, examination of the cytokine release profile in splenocytes from infected mice showed that infection was associated with an initial copious release of both IFN-gamma and IL-10. IL-10 production increased as the infection progressed, whereas IFN-gamma levels diminished. Infected mice were given repeated infusions of a rat mAb against mouse IL-10 or rat IgM. Examination of IgM serum levels in anti-IL-10-treated mice (infected or not) showed that depletion of endogenous IL-10 resulted in much decreased IgM levels. Results showed that infusions of large dosages of the monoclonal anti-IL-10 resulted in a very significantly diminished bacterial growth in the spleens. These findings indicate that IL-10 may have a negative impact on resistance to M. avium infections, due, at least in part, to decreased macrophage activity.
Protective immunity to Haemonchus contortus induced by immunoaffinity isolated antigens that share a phylogenetically conserved carbohydrate gut surface epitope.
Authors: Jasmer D P , Perryman L E , Conder G A , Crow S , McGuire T
Published: December 2022

Whole gut homogenates of the blood-sucking nematode Haemonchus contortus induce protective immunity in goats, and some of these gut Ag are conserved among related parasitic nematode species. To identify gut Ag that induce protective immunity and have phylogenetically conserved epitopes, mAb were made to gut-surface Ag of H. contortus. Forty-nine mAb reacted with microvilli of the parasite gut. Two of these mAb (42/10.6.1 and 42/53.3.5) were analyzed here. Both of the mAb bound to the microvillar surface of freshly isolated gut, and each mAb recognized carbohydrate epitopes, based on sensitivity to periodate oxidation. The 42/10.6.1 epitope occurred on at least 18 proteins in Western blots and in several H. contortus tissues. Proteins recognized by this mAb localized to membrane and excretory/secretory fractions of the worm. This epitope was also identified on the gut and other tissues and multiple proteins of related adult and larval nematodes, including larval Ancylostoma caninum and a mixed population of the free-living nematode Caenorhabditis elegans. In contrast, the 42/53.3.5 mAb bound to the gut surface and recognized proteins of 100 and 46 kDa from adult H. contortus gut. Four proteins of 100, 52, 46, and 30 kDa were isolated from the 42/53.3.5 immunoaffinity columns, and except for the 30-kDa protein, each was recognized by both the 42/10.6.1 and 42/53.3.5 mAb. Epitopes recognized by each mAb were distinct from one another and phosphorylcholine. When used to immunize goats, Ag isolated by both mAb induced protection that significantly (p < 0.05) reduced total worm counts after challenge infections compared with the control groups.
Molecular selection of human antibodies with an unconventional bacterial B cell antigen.
Authors: Sasano M , Burton D R , Silverman G J
Published: December 2022

Unconventional Ag for B cells that are comparable to known superantigens for T lymphocytes have not been well characterized. However, the bacterial membrane protein, Staphylococcal protein A (SpA), has sites that interact with the Fab of many IgM, IgA, IgG, and IgE, and in recent reports we have provided evidence of VH restriction in Fab that bind SpA. To investigate the molecular basis for this Fab binding specificity, we have selected monoclonal Fab from a phage-display combinatorial Ig library, based on the ability to bind SpA. By this approach, in an unselected human polyclonal IgG Fab library, about 17% of antibody-expressing clones were found to bind SpA. SpA binding was completely restricted to Fab with VH3 H chains, and about 60% of VH3 Fab in the unselected library had SpA binding capacity. Analysis of 21 VH sequences and 6 VL sequences demonstrated that Fab that bind SpA use diverse VH3 genes, while the L chains derive from a variety of V kappa and V lambda gene families. By creation of antibodies with differential H-L chain pairing, the global capacity to bind SpA was shown to be dictated by VH3 usage, but different L chain usage could result in up to a fourfold change in binding affinity. The apparent KD of the SpA binding by different Fab ranged from 2.5 x 10(-7) to > 10(-5) M. Furthermore, repeated rounds of in vitro panning selected for antibodies based on higher binding affinity. These data indicate that the pattern of VH family restriction of Ig reactive with SpA is comparable to known superantigens, and there is a hierarchy within the binding affinities of VH3 Fab based on V gene usage.
Bacterial superantigens induce rapid and T cell receptor V beta-selective down-regulation of L-selectin (gp90Mel-14) in vivo.
Authors: Miethke T , Wahl C , Holzmann B , Heeg K , Wagner H
Published: December 2022

Upon challenge of mice with bacterial superantigens such as staphylococcal enterotoxin B, several facets of TCR V beta-selective acute T-cell alterations can be observed, which include acute T cell priming, and systemic lymphokine release followed by ligand-specific unresponsiveness. Prompted by experiments showing that stimulation of T cells by phorbol esters in vitro results in rapid shedding of the L-selectin homing receptor, we investigated the expression of adhesion molecules on superantigen-responsive T cells in vivo. Here we show that bacterial superantigens cause TCR V beta-specific loss of L-selectin. Down-regulation of L-selectin was selective, since the expression of other lymphocyte surface receptors was not changed. L-Selectin down-regulation represents a superantigen-induced immediate cell surface alteration and was not observed on T cells stimulated by TCR-specific antibodies. Loss of expression was almost complete within 30 min, and recovered 50 h after challenge. The results suggest that acute loss of L-selectin is a hallmark of T cell activation by bacterial superantigens that may result in profound changes of T lymphocyte recirculation pathways.
The inhibition of different T cell lines specific for the same antigen with TCR antagonist peptides.
Authors: Snoke K , Alexander J , Franco A , Smith L , Brawley J V , Concannon P , Grey H M , Sette A , Wentworth P
Published: December 2022

To further understand and evaluate the phenomenon of TCR antagonism, we wished to determine whether analogs of an antigenic determinant could antagonize a specific polyclonal response. To this end, the ability of TCR antagonist peptides to inhibit a panel of five different DR4w4-restricted, influenza hemagglutinin 307-319-specific T cell lines was examined. An analysis of their V beta and J beta usage indicated that each of these five T cell lines expressed different TCR. A series of HA 307-319 single amino acid substituted analogs were used to determine the fine Ag specificities of the different lines. Ag analogs that demonstrated little or no stimulatory capacity were then examined for their ability to act as TCR antagonists by inhibiting the proliferative response of these five lines. Overall, 17 different peptide analogs capable of antagonizing at least one T cell line were identified. Although no single analog was capable of inhibiting all five T cell lines, two different analogs were identified that were capable of inhibiting four of five of the T cell specificities examined.
Comparative accessory cell function of human peripheral blood dendritic cells and monocytes.
Authors: Thomas R , Davis L S , Lipsky P E
Published: December 2022

The capacity of human peripheral blood (PB) dendritic cells (DC) and monocytes to facilitate T cell activation and the interaction molecules employed were compared. We have shown that precursors of DC constitute 2 to 3% of circulating PBMC, and can be isolated as CD33+CD14dim cells, whereas monocytes are CD33+CD14bright. Freshly obtained DC expressed similar densities of HLA-DR and the accessory molecules LFA-3, ICAM-1, and B7 as monocytes; after a 36-h incubation the expression of HLA-DR, ICAM-1, and B7 increased on both APC. Accessory cell function was examined in PB T cell cultures stimulated by suboptimal concentrations of immobilized mAb to CD3, and by stimulation of an allospecific T cell line. Freshly isolated monocytes and DC were comparable accessory cells in these assays, but their accessory function was increased by in vitro preincubation, although cultured DC and monocytes were comparably active. In contrast, DC were much more effective stimulators of freshly isolated allogeneic T cells than monocytes. DC were much more effective stimulators of freshly isolated allogeneic PB CD4+ naive and memory T cells than monocytes, whereas DC and monocytes were comparable accessory cells for memory and naive T cells stimulated with immobilized anti-CD3. The accessory molecules ICAM-1, LFA-3, and B7 were used comparably by DC and monocytes for accessory function in the presence of immobilized anti-CD3 and in the MLR, and none was unique for either APC population. These accessory molecules costimulated T cells in an additive fashion. Although immature blood DC and monocytes expressed minimal B7 and did not utilize it as an accessory molecule, B7 played an important role in the increased accessory function of differentiated APC. The results indicate that PB DC and monocytes function most efficiently after differentiation into mature cells that express increased amounts of MHC and other accessory molecules. Because DC and monocytes exhibit comparable accessory function in anti-CD3 T cell stimulation, differences in the expression of MHC molecules and/or their bound peptides are likely to explain the markedly enhanced capacity of DC to stimulate allogeneic PB T cells.
IL-2 stimulation of T lymphocytes induces sequential activation of mitogen-activated protein kinases and phosphorylation of p56lck at serine-59.
Authors: Watts J D , Welham M J , Kalt L , Schrader J W , Aebersold R
Published: December 2022

p56lck, a member of the src family of non-receptor protein tyrosine kinases, is expressed almost exclusively in cells of lymphoid origin. p56lck is known to associate with the T lymphocyte surface glycoproteins CD4 and CD8, and plays a critical role in both T lymphocyte development and activation. p56lck also associates with the beta-subunit of the IL-2R, and is activated when IL-2 binds to its receptor. Using primary cultures of Con A-activated normal splenic mouse T lymphocytes, we observed an IL-2-induced sequence of events involving p56lck. We saw a rapid (within 1 to 2 min) and transient increase in p56lck kinase activity, which preceded the activation of both the p42erk-2 and p44erk-1 mitogen-activated protein kinases, maximal activation of which was observed after 10 min. We also observed an IL-2-induced shift in the electrophoretic mobility of p56lck from an apparent molecular mass of 56 kDa (p56lck) to 60 kDa (p60lck), which reached a maximum at 15 min, the level of p60lck remaining constant for up to 4 h thereafter. This IL-2-induced shift correlated with the phosphorylation of serine-59 of p56lck, a site that mitogen-activated protein kinases are capable of modifying in vitro. The implications of these results for the understanding of both p56lck function and lymphoid cell receptor signaling pathways are discussed.
Structure and genomic organization of immunoglobulin light chain in the channel catfish. An unusual genomic organizational pattern of segmental genes.
Authors: Ghaffari S H , Lobb C J
Published: December 2022

Channel catfish L chain cDNA was obtained through a PCR strategy and used to isolate multiple L chain clones from cDNA and genomic libraries. Sequence analysis of full-length cDNA indicates that the V region is preceded by a leader peptide, and represented by framework and CDR regions. Both VL and CL domains contain the invariant cysteines and tryptophans as well as other phylogenetically conserved L chain residues. The sequence similarity of the catfish L chain with higher vertebrate kappa- and lambda-chains, however, does not readily allow the catfish L chain to be classified. Eight cDNA clones isolated from a cDNA library were shown to represent different processed derivatives of sterile L chain transcripts. These transcripts share a similar upstream sequence region and extend downstream to include a CL or alternatively a JL segment in partial germ-line configuration that has been spliced into a CL. Sequence comparisons indicate that these transcripts represent the product of different L chain loci. Genomic Southern blot analyses with VL and CL probes indicate that there are at least 30 VL segments and at least 15 CL segments. The analysis of 17 genomic L chain clones showed that each hybridized with VL-, JL-, and CL-specific probes. Characterization of the gene segments in three of these clones indicates a previously undescribed pattern of segmental gene organization. Gene segments are found in clusters with VL, JL, and CL segments in each cluster. Within a cluster VL segments reside upstream of single copies of closely linked JL and CL segments. The proximity of VL segments downstream from JL-CL segments suggests that individual clusters may be closely linked. The VL segments are located in opposite transcriptional polarity relative to the JL and CL gene segments, which indicates that VL segments are likely rearranged to JL-CL segments by inversion rather than deletion events.
Characterization of a C3 receptor on the envelope of Schistosoma mansoni.
Authors: Silva E E , Clarke M W , Podesta R B
Published: December 2022

The surface of the syncytial epithelium of the human parasite, Schistosoma mansoni, consists of an apical plasma membrane (APM) and an overlying envelope (En). The rapid turnover of these membranes is an adaptation to parasitism and is influenced by ambient signals emanating from the host's immune system. The third component of complement (C3) has been shown to stimulate the synthesis of the En via a C3-binding protein (C3bp) and a Ca(2+)-dependent signal transduction mechanism. Using ELISA the C3bp was found to be restricted to the En. In addition, cross-linking of iodinated C3 to En proteins with the homobifunctional noncleavable disuccinimidyl suberate reagent yielded a receptor-C3 complex in excess of 250 kDa, and SDS-PAGE analysis of solubilized En proteins that were radiolabeled and chromatographed on C3-Sepharose revealed a 130-kDa protein that specifically bound to the C3 beads. In further experiments, using a photoactivatable radiolabeled cross-linker, the Denny-Jaffe reagent, C3 transferred the radiolabel to a 130-kDa En protein. Metabolic labeling experiments have demonstrated that this C3bp is synthesized by the parasite and, more importantly, antibodies raised against the C3bp blocked En synthesis in vivo. Also, the surface localization of the C3bp was demonstrated using immunolabeling electron microscopy. The data presented herein strongly suggest that the 130-kDa schistosome En protein is a C3bp responsible for renewal of the En in response to C3 binding.
IFN inhibits inflammatory responses and protective immunity in mice infected with the nematode parasite, Nippostrongylus brasiliensis.
Authors: Urban J F , Madden K B , Cheever A W , Trotta P P , Katona I M , Finkelman F D
Published: December 2022

Mice infected with the gastrointestinal nematode parasite Nippostrongylus brasiliensis (Nb) develop responses associated with enhanced production of IL-4 (increased serum IgE levels and intestinal mucosal mastocytosis) and IL-5 (tissue and peripheral blood eosinophilia). The antagonistic effects of IFN on IL-4-mediated responses prompted an examination of the effects of IFN on the host response to Nb. Treatment with rIFN-alpha and rIFN-gamma induced a marked increase in parasite egg production (fecundity) in BALB/c mice infected with Nb and delayed intestinal expulsion of adult worms. Treatment with rIFN-alpha or rIFN-gamma also inhibited the rise in peripheral blood eosinophilia that follows inoculation with Nb, and the intensity of pulmonary perivascular tissue eosinophilia. However, Nb-induced increases in serum IgG levels and intestinal mastocytosis were only temporarily delayed by IFN. Induction of endogenous IFN production by injection of fixed Brucella abortus into mice infected with Nb also resulted in an increased worm fecundity and delayed adult worm expulsion. These effects were ablated when mice given Brucella abortus also received injections of neutralizing anti-IFN antibodies. Thus, IFN inhibit host protective immunity to Nb, perhaps by interfering with the production and effects of Th2 cytokines.
CD4+ type 1 and CD8+ type 2 T cell subsets in human leishmaniasis have distinct T cell receptor repertoires.
Authors: Uyemura K , Pirmez C , Sieling P A , Kiene K , Paes-Oliveira M , Modlin R L
Published: December 2022

The mechanism of protective immunity and immunologic resistance against intracellular pathogens is believed to involve the activation of Ag-specific T cells. The T cells involved in protection/resistance to Leishmania can be studied using localized American cutaneous leishmaniasis (LCL) as a model, because the disease is often self-healing. Our study was undertaken to identify specific T cell populations that had accumulated in LCL lesions on the basis of TCR V beta gene usage. RNA was derived from skin lesions and blood of eight LCL patients, as well as from purified CD4+ and CD8+ subsets from the lesions and blood of three patients. After synthesis of cDNA, V beta gene usage was assessed by polymerase chain reaction. In all eight patients, several V beta gene families were overrepresented in lesions compared to blood. More importantly, the TCR V beta repertoires of both lesional CD4+ and CD8+ subsets were skewed compared to the repertoire of the respective subsets in the blood of the same donor. The overrepresented V beta s in the CD4+ and CD8+ subsets from lesions were in most instances disparate, particularly with the V beta 6 TCR skewed in the lesional CD8+ subset. Not only were the TCR repertoires of the overrepresented V beta in the lesional CD4+ and CD8+ subsets generally distinct, but the cytokine mRNA expressed by these subsets were also discrete. Strikingly, the CD4+ subset was characterized by IFN-gamma mRNA expression and the CD8+ subset by IL-4 and IL-10 mRNA expression. These data indicate that the pathogenesis of human leishmaniasis may be explained by the balance of CD4+ type 1 and CD8+ type 2 T cells, which probably recognize distinct sets of Ag.
Association of all three types of Fc gamma R (CD64, CD32, and CD16) with a gamma-chain homodimer in cultured human monocytes.
Authors: Masuda M , Roos D
Published: December 2022

Receptors for the Fc region of IgG (Fc gamma R) on mononuclear phagocytes have been shown to play an important role in the removal of IgG-opsonized particles from the circulation. We found that all three types of Fc gamma R (CD64, CD32, and CD16) in cultured human monocytes are associated with the gamma-chain homodimer that is also present in the high affinity receptor for IgE. Immunoprecipitates of each of these Fc gamma R, prepared from 1% digitonin lysates of cultured human monocytes, incorporated phosphate into a gamma-chain homodimer when incubated with [gamma-32P]ATP. Fc gamma RII immunoprecipitates also incorporated phosphate into Fc gamma RII itself. When human alveolar macrophages were used, similar results were obtained. Although to a minor extent, each anti-Fc gamma R immunoprecipitate from freshly purified monocytes also coprecipitated gamma-chains. These Fc gamma R and gamma-chains did not constitute one large complex, because anti-Fc gamma RI or anti-Fc gamma RIII immunoprecipitates did not coprecipitate Fc gamma RII. In addition, F (ab')2 fragments of anti-Fc gamma R mAb bound to intact cells were recovered in the anti-gamma-chain immunoprecipitates but not in immunoprecipitates made with anti-Fc gamma RIII or anti-Fc gamma RII mAb. When recovery of radioactivity in anti-gamma-chain immunoprecipitates was compared with that in anti-mouse-Ig immunoprecipitates, approximately 25% of the Fc gamma RI and 20% of the Fc gamma RII expressed at the cell surface were associated with gamma-chains. The gamma-chains may play an important role in signal transduction via Fc gamma R in human macrophages.
Mature CD4+ T lymphocytes from MRL/lpr mice are resistant to receptor-mediated tolerance and apoptosis.
Authors: Bossu P , Singer G G , Andres P , Ettinger R , Marshak-Rothstein A , Abbas A K
Published: December 2022

The goal of this study was to examine the functional responses and tolerance susceptibility of T lymphocytes from mice of the autoimmune strain, MRL/lpr. A population of autoreactive CD4+ T cells can be readily expanded from the lymphoid tissues of young lpr mice. Lines of IL-2-producing autoreactive and alloreactive lpr and alloreactive +/+ T cells were developed to study their responses to tolerance-inducing stimuli. Culture of +/+ T cells with high concentrations of immobilized anti-CD3 antibody induces both functional anergy and apoptosis. By contrast, lpr-derived T cell lines are relatively resistant to anergy and apoptosis. The implications of these findings for the development of autoimmunity, and the possible role of the Fas Ag in determining resistance or susceptibility to tolerance, are discussed.
Use of C6-deficient rats to evaluate the mechanism of hyperacute rejection of discordant cardiac xenografts.
Authors: Brauer R B , Baldwin W M , Daha M R , Pruitt S K , Sanfilippo F
Published: December 2022

C plays a critical role in the hyperacute rejection (HAR) of discordant xenografts (Xg), but the relative contribution of early vs late C components is unknown. In this study, genetic differences in C6 activity were correlated with HAR of guinea pig cardiac Xg by the rat. Seven rat strains were tested for C activity. Six strains (PVG.R1 (R1), PVG.1A (1A), DA, W/F, F344, LEW) had readily detectable C activity in the total and alternative pathways. Some PVG rats also had adequate C activity [PVG (C+)] but others [PVG (C-)] had a profound C6 deficiency. All rats with adequate C activity (n = 35) rejected cardiac Xg between 15 and 80 min. PVG (C+) (n = 6) rats also rejected cardiac Xg hyperacutely (26 +/- 12 min), whereas PVG (C-) (n = 16) rats, which had high preformed IgM natural antibody titers, rejected cardiac Xg in 1 to 2 days (2678 +/- 542 min). Transfer of serum from R1 rats to PVG (C-) recipients with vigorously beating Xg caused HAR of cardiac Xg within 116 +/- 75 min. Transfer of fresh PVG (C-) serum or heat-inactivated R1 serum did not induce HAR. HAR was characterized by intravascular platelet aggregation and interstitial hemorrhage, whereas Xg transplanted to PVG (C-) recipients had patent vessels at 30 min but were heavily infiltrated by granulocytes and monocytes at 2 days. These findings indicate that a deficiency in C6 prevents HAR but allows an accelerated acute rejection that may be mediated by the generation of vasoactive and chemotactic C3a and C5a.
Regulation of anti-Sm autoantibodies by the immunoglobulin heavy chain locus.
Authors: Halpern M D , Craven S Y , Cohen P L , Eisenberg R A
Published: December 2022

Anti-Sm antibodies are specific markers for systemic lupus erythematosus in MRL mice and in humans. The prevalence of anti-Sm positivity in inbred MRL/Mp-lpr/lpr(MRL/lpr) mice is consistently about 25% at 5 mo of age, when the disease is at its peak. The control of the development of anti-Sm in individual MRL/lpr mice has been shown to be the result of stochastic factors, and previous research has indicated that the immunoglobulin heavy chain (IgH) b allotype may be more amenable to the production of anti-Sm. We have now further investigated the influence of the IgH genetic locus on the production of anti-Sm and other autoantibodies in an allotype congenic MRL strain, the MRL/Mp-Ipr/Ipr-IgHb (MRL/lpr-IgHb). Strikingly, 78% of MRL/lpr-IgHb mice produced anti-Sm, compared with 27% of contemporaneous MRL/lpr (IgHj) mice. Of those mice that were positive for anti-Sm, the MRL/lpr-IgHb strain produced significantly higher levels of anti-Sm than did the anti-Sm positive MRL/lpr mice. No differences were observed between the conventional MRL/lpr and the MRL/lpr-IgHb levels of antichromatin, anti-ssDNA, antiribosomal P, or anti-Su. In addition, kidney function, which was assessed by measuring serum urea nitrogen levels, was similar in the two strains. These results support the notion that the control of anti-Sm production in MRL/lpr mice operates through the IgH locus.
Differentiation of encephalitogenic T cells confers resistance to an inhibitory anti-CD4 monoclonal antibody.
Authors: Mannie M D , Morrison-Plummer J , McConnell T J
Published: December 2022

The anti-CD4 mAb W3/25 inhibits experimental autoimmune encephalomyelitis (EAE) in Lewis rats by blocking Th cell responses to encephalitogenic determinants of myelin basic protein (MBP). However, it has yet to be resolved how W3/25 modulates CD4 to inhibit EAE-associated T cell responses. This study revealed that W3/25 profoundly inhibited MBP-stimulated proliferation by sensitized lymph node cells but only partially inhibited the respective response of uncloned and cloned lines of MBP-specific T cells. That is, low concentrations of W3/25 blocked 30 to 60% of MBP-stimulated proliferation, but 100-fold higher concentrations did not result in additional inhibition. W3/25 also inhibited MBP-induced acquisition of EAE transfer activity, but only in cultures of freshly isolated lymph node cells and not in cultures of continuously propagated T cells. Studies focusing on the GP2.E5 T cell line revealed that the lack of sensitivity to W3/25 in encephalitogenic and proliferative assays was nevertheless associated with an effective blockage of MBP-stimulated IL-2 production. Importantly, W3/25 specifically inhibited antigenic but not mitogenic stimulation of IL-2 production. Reverse transcriptase/polymerase chain reaction analyses revealed that MBP-activated GP2.E5 T cells produced mRNA for both IL-2 and IL-4, and that W3/25 selectively inhibited accumulation of IL-2 as compared to IL-4 mRNA. Thus, GP2.E5 T cells apparently express a IL-4-dependent pathway that confers resistance to the inhibitory activity of W3/25. Studies focusing on two CD4+ T cell hybridomas revealed that W3/25 profoundly inhibited MBP-stimulated IL-2 production but did not affect the alternative response of MBP-induced growth inhibition. Several other hybrids also mediated MBP-stimulated IL-2 production but did not express CD4 and were not affected by W3/25. These results indicate that: 1) interactions of W3/25 with CD4 do not necessarily block class II MHC-restricted recognition of MBP; and 2) expression of CD4 is not necessary for Ag recognition by several clonotypes of MBP-reactive T cells. Rather, the results of this study are consistent with the concept that W3/25 inhibits transduction of costimulatory signals that are required specifically for initiation of IL-2 production. These findings may have important implications for understanding the therapeutic potential of anti-CD4 mAb in autoimmune disease.
MHC-linked low-molecular mass polypeptide subunits define distinct subsets of proteasomes. Implications for divergent function among distinct proteasome subsets.
Authors: Brown M G , Driscoll J , Monaco J J
Published: December 2022

Proteasomes are 650-kDa, multisubunit endopeptidases that might be involved in the MHC class I Ag processing pathway. We demonstrate the existence of multiple structurally distinct subsets of proteasomes. Distinct forms of proteasomes share a hypothetical core to which unique subunits are added. One of these subsets, LMP2+ proteasome, contains the product of the MHC-linked Lmp-2 gene, and can be distinguished serologically and structurally from other proteasome subsets. The expression of LMP2+ and LMP2- proteasomes is variable among cell lines of different tissue types, and their relative abundance and subunit composition are regulated by IFN-gamma. LMP2+ proteasomes comprise 0 to 74% of total cellular proteasomes. Both LMP2+ and LMP2- proteasomes are proteolytically active. We suggest proteasome function might be regulated by subunit composition, and some, or all proteasome subsets, might participate in the production or delivery of peptides to MHC class I molecules. Both LMP2+ and LMP2- subsets can be further subdivided on the basis of the presence or absence of other unique subunits. Implications of the existence of structurally distinct forms of proteasomes in different tissue types is discussed.
Th1 cell anergy and blockade in G1a phase of the cell cycle.
Authors: Gilbert K M , Weigle W O
Published: December 2022

Human gamma-globulin (HGG)-specific Th1 cells exposed to HGG presented by chemically fixed spleen cells are blocked in G1a phase when challenged subsequently with HGG. The present study made use of the G1a blocker n-butyrate to further examine the relationship between tolerance induction and cell cycle progression. Th1 cells from primary cultures containing n-butyrate together with HGG and immunogenic, nonfixed APC lost their ability to proliferate or secrete IL-2 in HGG-stimulated secondary cultures. In contrast to their lack of responsiveness to secondary Ag challenge, Th1 cells exposed to n-butyrate and HGG proliferated normally in secondary cultures stimulated with IL-2. The suppressive effects of n-butyrate appear to require TCR occupation; Th1 cells exposed to n-butyrate in the absence of HGG did not lose their ability to proliferate in Ag-stimulated secondary cultures. In addition, although both HGG-presenting APC and IL-2 stimulate Th1 cell cycle progression into G1a, only HGG-presenting APC induced Th1 cell anergy in conjunction with n-butyrate. Unlike n-butyrate, drugs that blocked Th1 cell cycle progression in G0, G1b, or S/G2 phases did not inhibit subsequent Ag-specific proliferation by Th1 cells. Thus it appears that n-butyrate-induced G1a sequestration, in association with TCR occupancy, induces Th1 cell anergy.
A novel functional cell surface dimer (kp43) serves as accessory molecule for the activation of a subset of human gamma delta T cells.
Authors: Rubio G , Aramburu J , Ontañón J , López-Botet M , Aparicio P
Published: December 2022

Kp43 is a cell surface molecule expressed by NK cells, gamma delta T lymphocytes, and a small subset of CD56+ alpha beta T cells. In the present study the distribution and function of Kp43 on gamma delta T cells is described. The expression of Kp43 on freshly isolated gamma delta T-cell populations derived from fetal and adult tissues was biased toward memory V gamma 2+/V delta 2+ T lymphocytes and appeared to be up-regulated after activation. Several gamma delta T-cell clones were derived from different sources. Adult V gamma 2+/V delta 2+ T-cell clones expressed the highest levels of Kp43, V delta 1 T-cell clones derived from periphery expressed moderate levels, whereas some thymus V delta 1 T cells and fetal gamma delta T-cell clones displayed low or undetectable levels of Kp43 molecule. Based on the effect of a specific mAb, this dimer appears to be fully functional as previously shown for NK cells. The stimulation of Kp43+ gamma delta T-cell clones with a combination of anti-CD3 and anti-Kp43 co-immobilized on a solid substratum enhanced both the expression of cell surface CD25 and the secretion of TNF-alpha. The restricted expression and functional activity of the Kp43 dimer suggests that it may play an important regulatory role in activation, selection, Ag recognition, and responsiveness of a subset of gamma delta T cells.
Targeted disruption of CD43 gene enhances T lymphocyte adhesion.
Authors: Manjunath N , Johnson R S , Staunton D E , Pasqualini R , Ardman B
Published: December 2022

CD43 is a major leukocyte surface glycoprotein thought to have important functions for T lymphocyte adhesion and activation. We investigated the function of CD43 by using gene targeting to eliminate CD43 expression in the human T lymphocyte line CEM and then testing their adhesive phenotype. Loss of CD43 expression by the CEM cells enhanced their homotypic adhesion and binding to two distinct ligands, fibronectin and HIV-1 gp120. The enhanced homotypic adhesion was blocked specifically by an anti-beta 1 integrin mAb, and the enhanced binding to fibronectin and gp120 was blocked specifically by anti-beta 1 integrin and anti-CD4 mAb, respectively. Partial reconstitution of CD43 expression in the CD43-negative cells resulted in a corresponding reversion to a less adhesive phenotype. These data suggest that CD43 interferes with T lymphocyte adhesion and that CD43 can regulate lymphocyte adhesion by providing a threshold that must be overcome for cell-cell and cell-ligand interactions to occur.
Corticotropin-releasing hormone in synovial fluids and tissues of patients with rheumatoid arthritis and osteoarthritis.
Authors: Crofford L J , Sano H , Karalis K , Friedman T C , Epps H R , Remmers E F , Mathern P , Chrousos G P , Wilder R L
Published: December 2022

Inflammation normally results in enhanced synthesis and secretion of hypothalamic corticotropin-releasing hormone (CRH) which, in turn, exerts antiinflammatory effects by virtue of increased adrenal glucocorticoid production. CRH and CRH binding sites are also expressed in the peripheral nervous and immune systems. Our groups have recently shown that CRH is secreted locally in acute carrageenin-induced inflammation in rats and has predominantly proinflammatory effects. We have also shown that CRH is expressed in the joints of Lewis rats with experimental arthritis. To determine if CRH is present in human inflammatory arthritis, we examined synovial fluids and tissues from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) and normal individuals. We found markedly enhanced expression of immunoreactive CRH in situ in synovium from patients, which was significantly greater in RA than in OA (p < 0.01). CRH concentrations were also significantly higher in RA (140 +/- 33 pg/ml, mean +/- SEM; n = 10) than OA (25 +/- 4 pg/ml; n = 6) synovial fluids (p < 0.005). HPLC showed immunoreactive CRH extracted from RA and OA synovial tissues and fluids coeluted with CRH 1-41. CRH mRNA was present in low levels in synovial tissue from patients with RA and, to a lesser extent, OA. In summary, immunoreactive CRH is locally secreted in the synovium of patients with RA and, at lower levels, OA. These data support the view that CRH functions as an autocrine and/or paracrine mediator of inflammation in humans.
Antigen-specific induction of antibodies against native mammalian DNA in nonautoimmune mice.
Authors: Desai D D , Krishnan M R , Swindle J T , Marion T N
Published: December 2022

Spontaneous anti-DNA antibodies in autoimmune mice have the characteristics of antibody produced by Ag-specific, clonally selective B cell stimulation. The nature of the somatically derived antibody V region structures recurrent among spontaneous anti-DNA antibodies suggests that DNA or DNA-protein complexes may provide the antigenic stimulus for autoimmune anti-DNA antibody. In order to test this hypothesis directly, we have immunized normal, nonautoimmune-predisposed mice with complexes formed with DNA and an immunogenic, DNA-binding peptide. The highly immunogenic peptide, Fus1, forms an internal domain of a 128-amino acid ubiquitin-fusion protein from Trypanosoma cruzi. DNA-Fus1 complexes formed with native calf thymus DNA induced anti-DNA antibody in normal, nonautoimmune-predisposed mice that is similar in isotype and specificity to spontaneous anti-DNA antibody in (NZB x NZW)F1 autoimmune mice. The progressive nature of the development of dsDNA specificity in the immunized mice was also analogous to what is observed in the spontaneous anti-DNA antibody response of autoimmune (NZB X NZW)F1 mice. DNA-Fus1 immunized mice that produced IgG that bound to dsDNA had low to moderate levels of proteinuria and glomerular deposits of IgG. This experimental immunization system may be useful for understanding the immunologic basis for autoimmunity to DNA.
Role of IL-1 and tumor necrosis factor in coxsackie virus-induced autoimmune myocarditis.
Authors: Lane J R , Neumann D A , Lafond-Walker A , Herskowitz A , Rose N R
Published: December 2022

We have previously reported that B10.A (H-2a) mice, which are resistant to the induction of postcoxsackievirus autoimmune myocarditis, become susceptible upon treatment with LPS, IL-1, or TNF. In this study, we show that the development of autoimmune myocarditis is associated with infiltration of the heart by inflammatory cells that secrete the cytokines IL-1 and TNF. Local secretion of these cytokines contributes to increased levels of IL-1 and TNF in the serum. Thus, local production of cytokines promotes the induction of this postinfectious autoimmune disease.
Neutralization and infection-enhancement epitopes of influenza A virus hemagglutinin.
Authors: Tamura M , Webster R G , Ennis F A
Published: December 2022

We studied 18 mAb specific for the H3 hemagglutinin (HA) to analyze the relationships between neutralizing and infection-enhancing epitopes on the influenza HA. The mAb could be separated into three groups based on their neutralization (N) and enhancement (E) activity in assays with the prototype virus; group I (N+E+), group II (N+E-) and group III (N +/- E+). A representative mAb from each group was analyzed for its effect on the infectivity of a group of escape mutants, selected with mAb to three sites on the H3 HA, and wild-type H3 viruses to define the relationship between neutralizing epitopes and infection-enhancing epitopes. A group I mAb (N+E+), which recognized site A on the HA, neutralized virus infection at high concentrations of antibody and enhanced virus infection at low concentrations. A group II mAb (N+E-), which recognized site B, had high neutralizing but no enhancing activity. The failure of this mAb to enhance virus uptake was a result of the inability of the Fc portion of virus-mAb complexes to bind to Fc receptor. The addition of anti-murine IgG as a second antibody to these virus-mAb complexes augmented virus uptake. A group III mAb (N +/- E+), which recognized site C, had enhancing but little neutralizing activity. This is the first definition of distinct epitopes that induce neutralizing and/or enhancing mAb.
Platelet-activating factor triggers the phosphorylation and activation of MAP-2 kinase and S6 peptide kinase activity in human B cell lines.
Authors: Franklin R A , Mazer B , Sawami H , Mills G B , Terada N , Lucas J J , Gelfand E W
Published: December 2022

Platelet activating factor (PAF), a phospholipid mediator produced by a variety of cell types, has potent biological activities in many cellular systems. We report that stimulation of B cell lines with PAF induced tyrosine phosphorylation of a protein, approximately 42 kDa in size. The PAF receptor antagonist WEB 2086 as well as the structural analogue PAF antagonist CV3988 inhibited the response, demonstrating that the tyrosine phosphorylation was attributable to PAF binding to a specific receptor. Immunoblot analysis, using an antibody to microtubule-associated protein-2 kinase, demonstrated the presence of a single protein species in unstimulated cells. PAF treatment induced the appearance of an additional species with a slightly reduced mobility in the gel. This PAF-inducible band had the same mobility on SDS-PAGE gels as the protein that was tyrosine-phosphorylated after PAF stimulation. Tyrosine phosphorylation of the 42-kDa protein was rapid, detectable within 30 s, and evident over a wide range of PAF concentrations (10(-7) to 10(-10) M). Treatment of cells with phorbol myristate acetate induced tyrosine phosphorylation of a protein with the same mobility in SDS-PAGE gels as the protein induced after PAF stimulation. Lysates from PAF-stimulated lymphoblastoid cells exhibited more than twice the ability to phosphorylate myelin basic protein than lysates from untreated cells. In addition, the ribosomal S6 peptide kinase activity (S6PK) was increased after PAF stimulation of the B cells. Taken together, the results suggest that PAF stimulation of B cells induces the tyrosine phosphorylation and activation of microtubule-associated protein-2 kinase.
Superantigen-driven peripheral deletion of T cells. Apoptosis occurs in cells that have lost the alpha/beta T cell receptor.
Authors: Huang L , Crispe I N
Published: December 2022

Injection of lymphoid cells expressing minor lymphocyte-stimulating antigen-1 (Mls-1a) induces tolerance to the superantigen, and partial deletion of Mls-1a-reactive T cells. We have identified a transient population of T cells that have lost the alpha/beta T cell receptor at the time when Mls-1a-reactive T cells start to disappear during the process of tolerance induction. Apoptosis was directly demonstrated in this TCR-alpha/beta negative T-cell population. This indicates a peripheral T-cell deletion pathway, characterized by TCR down-regulation, apoptosis, and clonal deletion. The consequence of Mls-1a-induced TCR down-regulation appears to be different in CD4+ cells and in CD8+ cells. Although most of the CD4+ cells that have lost TCR expressing alpha- and beta-chains appear to be undergoing apoptosis, many of their CD8+ counterparts may be able to re-express the Ag receptor. This argues for the involvement of coreceptors in the induction of apoptosis during peripheral deletion.
Immunodominance: a single amino acid substitution within an antigenic site alters intramolecular selection of T cell determinants.
Authors: Liu Z , Williams K P , Chang Y H , Smith J A
Published: December 2022

The mechanism of immunodominance was studied by mutating a single amino acid residue within an immunodominant determinant of Staphylococcus aureus nuclease (Nase). Residues 81 to 100, which can be further reduced to 86 to 100, were determined to be the immunodominant determinant of Nase in H-2k mice. By introducing selected single amino acid substitutions into the peptide encompassing residues 86 to 100 (p86-100), residue 90 was shown to be one of the critical amino acids for T cell recognition, inasmuch as most of the T cells recognizing p86-100 do not respond to a p86-100 analog with a substitution of leucine for alanine at the residue 90. A mutant of Nase with a replacement of alanine by leucine at residue 90 (A90L) was constructed, and for A90L region 112 to 130, which is a subdominant determinant in Nase, becomes immunodominant. Although unable to respond to Nase, T cells primed in vivo with the peptides covering various cryptic determinants proliferate when challenged with A90L in vitro. Our results suggest that at the protein level there is competition among potential T cell determinants of protein Ag for binding to MHC molecules, and that this competition plays a role in determining which determinant may become immunodominant.
Characterization of transcripts from unrearranged V alpha 8 genes in the thymus.
Authors: Holman P O , Roth M E , Huang M , Kranz D M
Published: December 2022

The genes that encode the alpha- and beta-chains of the TCR undergo programmed rearrangement during differentiation of a T cell in the thymus, but it is not known what controls the order and specificity of the rearrangement event. By analogy with Ig genes, it is possible that transcription of an unrearranged V region gene may be necessary for "access" of the recombinase. To begin to address this issue, the six members of the V alpha 8 subfamily (five functional members and a pseudogene) from C57Bl/6 mice were examined. Consistent with the "accessibility" model, we show that unrearanged V alpha 8 genes are specifically expressed in the thymus of adult mice. Each of the functional genes was transcribed, but at different levels in the thymus. The five V alpha 8 genes were identical through the first 50 nucleotides of the 3' flanking region, and each contained an open reading frame that was contiguous with the V coding region. More interestingly, two of these putative proteins ended in Cys-X-Cys, a motif that is known to undergo isoprenoid modification. This finding and the conservation in the region that extends beyond the heptamer-nonamer region raise the possibility that some unrearranged V genes may encode proteins that have a novel function during early T cell development.