bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevention of systemic lupus erythematosus in autoimmune BXSB mice by a transgene encoding I-E alpha chain.
Authors: Merino R , Iwamoto M , Fossati L , Muniesa P , Araki K , Takahashi S , Huarte J , Yamamura K , Vassalli J D , Izui S
Published: June 2004

Males from the BXSB murine strain (H-2b) spontaneously develop an autoimmune syndrome with features of systemic lupus erythematosus (SLE), which results in part from the action of a mutant gene (Yaa) located on the Y chromosome. Like other H-2b mice, the BXSB strain does not express the class II major histocompatibility complex antigen, I-E. Here we report that the expression of I-E (E alpha dE beta b) in BXSB males bearing an E alpha d transgene prevents hypergammaglobulinemia, autoantibody production, and subsequent autoimmune glomerulonephritis. These transgenic mice bear on the majority of their B cells not only I-E molecules, but also an I-E alpha chain-derived peptide presented by a higher number of I-Ab molecules, as recognized by the Y-Ae monoclonal antibody. The I-E+ B cells appear less activated in vivo than the I-E- B cells, a minor population. This limited activation of the I-E+ B cells does not reflect a functional deficiency of this cell population, since it can be stimulated to IgM production in vitro by lipopolysaccharides at an even higher level than the I-E- B cell population. The development of the autoimmune syndrome in the transgenic and nontransgenic bone marrow chimeric mice argues against the possibility that the induction of regulatory T cells or clonal deletion of potential autoreactive T cells as a result of I-E expression is a mechanism of the protection conferred by the E alpha d transgene. We propose a novel mechanism by which the E alpha d transgene protects BXSB mice against SLE: overexpression of I-E alpha chains results in the generation of excessive amounts of a peptide displaying a high affinity to the I-Ab molecule, thereby competing with pathogenic autoantigen-derived peptides for presentation by B lymphocytes and preventing their excessive stimulation.
Immature surface Ig+ B cells can continue to rearrange kappa and lambda L chain gene loci.
Authors: Rolink A , Grawunder U , Haasner D , Strasser A , Melchers F
Published: June 2004

Pro and pre B cells possess the long-term capacity to proliferate in vitro on stromal cells and interleukin 7 (IL-7) and can differentiate to surface immunoglobulin (sIg+) cells upon removal of IL-7 from the cultures. A key event in this differentiation is the extensive cell loss due to apoptosis. Because the proto-oncogene bcl-2 can promote cell survival, we established pre-B cell lines from E mu-bcl-2 transgenic mice. These pre-B cells have the same properties as those derived from non-bcl-2 transgenic mice except that they do not die by apoptosis. This allowed us to study the fate of newly formed B cells in vitro for a longer period of time. Here we show that early during the differentiation of pre-B cells, upregulation of RAG-1 and RAG-2 expression go hand in hand with rearrangements of the Ig gene loci. Moreover, the newly formed sIg+ B cells continue to express RAG-1 and RAG-2 and continue to rearrange L chain gene loci, even in the absence of proliferation, in an orderly fashion, so that kappa L+ sIg+ cells can become lambda L+ sIg+ or sIg- cells, whereas lambda L+ sIg+ cells can become sIg-, but not kappa L+ sIg+ cells. Thus, deposition of a complete Ig molecule on the surface of a B cell does not automatically stop the Ig-rearrangement machinery.
Characterization of c-kit positive intrathymic stem cells that are restricted to lymphoid differentiation.
Authors: Matsuzaki Y , Gyotoku J , Ogawa M , Nishikawa S , Katsura Y , Gachelin G , Nakauchi H
Published: June 2004

We found that c-kit-positive, lineage marker-negative, Thy-1lo cells are present in both bone marrow and thymus ("BM c-kit" and "thymus c-kit" cells). Although the two cell types are phenotypically similar, only BM c-kit cells showed the potential to form colonies in vitro as well as in vivo. However, both of them revealed extensive growth and differentiation potential to T cells after direct transfer into an irradiated adult thymus, or a deoxyguanosine-treated fetal thymus. Time course analysis showed that thymus c-kit cells differentiated into CD4CD8 double-positive cells approximately 4 d earlier than BM c-kit cells did. In addition, anti-c-kit antibody blocked T cell generation of BM c-kit cells but not of thymus c-kit cells. Intravenous injection of thymus c-kit resulted in the generation of not only T cells, but B as well as NK1.1+ cells. These data provide evidence that thymus c-kit cells represent common lymphoid progenitors with the differentiation potential to T, B, and possibly NK cells. The c-kit-mediated signaling appears to be essential in the transition from BM c-kit to thymus c-kit cells.
Helper T cell subsets for immunoglobulin A responses: oral immunization with tetanus toxoid and cholera toxin as adjuvant selectively induces Th2 cells in mucosa associated tissues.
Authors: Xu-Amano J , Kiyono H , Jackson R J , Staats H F , Fujihashi K , Burrows P D , Elson C O , Pillai S , McGhee J R
Published: June 2004

Antigen-specific B cell responses to mucosally delivered proteins are dependent upon CD4-positive T helper (Th) cells, and the frequency of Th1 and Th2 cell responses after oral immunization may determine the level and isotype of mucosal antibody responses. We have used a protein-based vaccine, tetanus toxoid (TT), together with the mucosal adjuvant cholera toxin (CT), for oral immunization of mice to study the nature of antigen-specific Th cell subsets induced in Peyer's patches (PP) of the gastrointestinal (GI) tract and in the spleen (SP) during peak antibody responses. Mice orally immunized with TT and CT responded with antigen-specific secretory immunoglobulin A (S-IgA) antibodies in the GI tract, and with both IgG and IgA antibody responses in serum. PP and SP CD4+ T cells from mice orally immunized with TT plus CT were cultured with antigen-coated latex microspheres for induction of proliferative responses and for enumeration of cytokine producing CD4+ T cells. Interestingly, both PP and SP CD4+ T cell cultures showed increased numbers of IL-4- and IL-5 (Th2-type)-producing, spot-forming cells (SFCs) after 21 d of immunization, while essentially no interferon-gamma (IFN-gamma) or IL-2 (Th1-type) SFCs were noted. Cytokine-specific Northern blots and RT-PCR also revealed that significant IL-4 and IL-5 mRNA levels, but not IFN-gamma or IL-2 mRNA, were present in CD4+ T cells isolated from antigen-stimulated cultures. However, systemic immunization with TT and CT induced antigen-specific IgG and IgM but not IgA antibodies in serum. Further, both IL-2 and IFN-gamma-producing Th1-type cells as well as IL-4- and IL-5-secreting Th2-type cells were generated in SP. Our results show that oral immunization with TT and the mucosal adjuvant CT selectively induced antigen-specific Th2-type responses which may represent the major helper cell phenotype involved in mucosal IgA responses in the GI tract.
Molecular characterization of a cross-reactive idiotope on human immunoglobulins utilizing the VH4-21 gene segment.
Authors: Potter K N , Li Y , Pascual V , Williams R C , Byres L C , Spellerberg M , Stevenson F K , Capra J D
Published: June 2004

The anti-idiotypic (anti-Id) antibody (Ab) 9G4 binds a cross-reactive idiotope (CRI) present in a select group of human autoantibodies. This Id has been localized to the portion of immunoglobulin (Ig) heavy (H) chains encoded by the VH4-21 gene segment, a member of the human VH4 family. This gene segment is utilized by essentially all cold agglutinin (CA) Abs with I/i specificity isolated from patients with CA disease stemming from chronic lymphoproliferative disorders. In this study, mutational analysis of a CA has been used to determine the structural basis for 9G4 binding to Abs utilizing the VH4-21 gene segment. Recombinant CA H chain mutants were produced and their 9G4 reactivity determined. Mutants were generated by exchanging VH4-21 sequences in the FR1, CDR1, and CDR2 with corresponding sequences from a closely related gene segment V71-2, a VH4 family member that is associated neither with Abs having CA activity nor with Abs that react with 9G4. The results indicate that the motif AVY at amino acid positions 23-25 in FR1 defines the 9G4 idiotope. Reaction of these recombinant Abs with a polyclonal rabbit anti-CA antiserum absorbed to render it specific for a CA CRI also maps predominantly to FR1. These findings indicate that the solvent-exposed FR1 plays an important role in eliciting an immune response to Igs.
Suppressive effect of antibody on processing of T cell epitopes.
Authors: Watts C , Lanzavecchia A
Published: June 2004

Immunoglobulins drive efficient antigen capture by antigen presenting cells for processing and presentation on class II MHC-molecules. High affinity antibody/antigen interactions are stable at endosomal/lysosomal pH thus altering the substrate for antigen processing. We show that this can result in strong suppression of presentation of some T cell epitopes. This effect was observed when the antibody specificity was a B cell surface Ig, or formed part of an immune complex. In the latter case the presence of the suppressing antibody boosts presentation of other T cell epitopes through enhanced uptake into Fc receptor bearing cells. The influence of bound antibodies on the outcome of antigen processing may influence with T cell epitopes dominate T cell responses and may change the focus of the response with time.
In vivo CD40-gp39 interactions are essential for thymus-dependent humoral immunity. II. Prolonged suppression of the humoral immune response by an antibody to the ligand for CD40, gp39.
Authors: Foy T M , Shepherd D M , Durie F H , Aruffo A , Ledbetter J A , Noelle R J
Published: June 2004

The ligand for CD40 has been recently identified as a 39-kd protein, gp39, expressed on the surface of activated CD4+ T helper cells (Th). In vitro, soluble CD40 and anti-gp39 have been shown to block the ability of Th to activate B cells, suggesting that gp39-CD40 interactions are important to T cell-dependent B cell activation. Here it is shown that in vivo administration of anti-gp39 dramatically reduced both primary and secondary humoral immune responses to erythrocytes and soluble protein antigens without altering responses to the T-independent type II antigen, trinitrophenyl-Ficoll. Treatment of mice for 4 d with anti-gp39 inhibited the anti-sheep red blood cell (SRBC) response for at least 3 wk and inhibited the expression of all immunoglobulin isotypes in secondary responses to the protein antigen, keyhole limpet hemocyanin. To examine the direct effect of anti-gp39 on Th function, SRBC-immune Th cells from anti-gp39-treated mice were adoptively transferred and shown to be fully capable of providing help. These results suggest that anti-gp39 treatment does not cause Th deletion or anergy. Anti-gp39 may mediate its profound immunosuppressive effects on humoral immunity by blocking gp39-CD40 interactions. Moreover, these studies establish gp39-CD40 as an important receptor-ligand pair for the targeting of therapeutic antibodies to control thymus-dependent humoral responses.
Inhibition of T cell and antibody responses to house dust mite allergen by inhalation of the dominant T cell epitope in naive and sensitized mice.
Authors: Hoyne G F , O'Hehir R E , Wraith D C , Thomas W R , Lamb J R
Published: June 2004

Antigen-specific CD4+ T cells play an important role in the allergic immune response to house dust mite (HDM) allergens in humans. The group 1 allergen of Dermatophagoides spp. is a major target antigen in both B and T cell recognition of HDM. In vitro studies have shown that the presentation of peptides to human T cells under appropriate conditions may lead to a state of specific nonresponsiveness. Therefore, to determine if peptides are able to modulate the function of allergen-reactive T cells in vivo, we have used a murine model of T cell recognition of the HDM allergen Der p 1. The results demonstrate that inhalation of low concentrations of peptide containing the major T cell epitope of Der p 1 (residues 111-139), induces tolerance in naive C57BL/6J mice such that they become profoundly unresponsive to an immunogenic challenge with the intact allergen. When restimulated in vitro with antigen, lymph node T cells isolated from tolerant mice secrete very low levels of interleukin 2, proliferative poorly, and are unable to provide cognate help to stimulate specific antibody production. Furthermore, intranasal peptide therapy was able to inhibit an ongoing immune response to the allergen in mice and this has potential implications in the development of allergen-based immunotherapy.
A major costimulatory molecule on antigen-presenting cells, CTLA4 ligand A, is distinct from B7.
Authors: Wu Y , Guo Y , Liu Y
Published: June 2004

CTLA4 ligands are important costimulatory molecules because soluble CTLA4Ig blocks the induction of T cell responses and induces T cell tolerance. As CTLA4 immunoglobulin (CTLA4Ig) binds B7 when the latter is expressed on fibroblasts, it was widely assumed that CTLA4Ig blocks T cell costimulation by blocking the function of B7. Here we show that the major costimulatory ligand bound by CTLA4Ig (which we term CTLA4 ligand A) on antigen-presenting cells are not encoded by the B7 gene. CTLA4 ligand A also differs from B7 in cellular distribution and in the respective levels of expression. Both B7 and CTLA4 ligand A are critically involved in T cell costimulation.
Regulation of thymocyte development through CD3. II. Expression of T cell receptor beta CD3 epsilon and maturation to the CD4+8+ stage are highly correlated in individual thymocytes.
Authors: Levelt C N , Carsetti R , Eichmann K
Published: June 2004

Recent studies have shown that maturation of CD4-8- double negative (DN) thymocytes to the CD4+8+ double positive (DP) stage is dependent on expression of the T cell receptor (TCR)-beta polypeptide. The exact mechanism by which the TCR-beta chain regulates this maturation step remains unknown. Previous experiments had suggested that in the presence of some TCR+ thymocytes, additional DN thymocytes not expressing a TCR-beta chain may be recruited to mature to the DP stage. The recent demonstration of an immature TCR-beta-CD3 complex on early thymocytes lead to the alternative hypothesis that signal transduction through an immature TCR-CD3 complex may induce maturation to the DP stage. In the latter case, maturation to the DP stage would depend on the expression of TCR-beta-CD3 in the same cell. We examined these two hypotheses by studying the expression of the intra- and extracellular CD3 epsilon, CD3 zeta, and TCR-beta polypeptides in intrathymic subpopulations during embryogenesis. CD3 epsilon and CD3 zeta were expressed intracellularly 2 and 1 d, respectively, before intracellular expression of the TCR-beta chain, potentially allowing immediate surface expression of an immature TCR-beta-CD3 complex as soon as functional rearrangement of a TCR-beta gene locus has been accomplished. Calcium mobilization could be induced by stimulation with anti-CD3 epsilon mAb as soon as intracellular TCR-beta was detectable, suggesting that a functional TCR-beta-CD3 complex is indeed expressed on the surface of early thymocytes. From day 17 on, most cells were in the DP stage, and over 95% of the DP cells expressed on the TCR-beta chain intracellularly. At day 19 of gestation, extremely low concentrations of TCR-beta chain and CD3 epsilon were detectable on the cell surface of nearly all thymocytes previously thought to be TCR-CD3 negative. These findings strongly support the hypothesis that maturation to the DP stage depends on surface expression of and subsequent signal transduction through an immature TCR-beta-CD3 complex and suggest that maturation to the DP stage by recruitment, if it occurs at all, is of minor relevance.
Enhanced antigen presentation in the absence of the invariant chain endosomal localization signal.
Authors: Anderson M S , Swier K , Arneson L , Miller J
Published: June 2004

The cytosolic tail of the major histocompatibility complex class II-associated invariant chain (Ii) molecule is thought to contain the endosomal localization signal that directs and/or retains newly synthesized class II within the endosomal antigen processing compartment. To determine the role of this signal in class II transport and antigen presentation we have generated class II-positive L cell transfectants that coexpress wild type or truncated forms of Ii. Deletion of the endosomal localization signal from Ii results in rapid transport of class II-Ii complexes to the cell surface. Once at the cell surface, the complex is efficiently internalized, Ii is degraded, and class II free of Ii is recycled back to the plasma membrane. Interestingly, the truncated form of Ii is still able to increase the efficiency of antigen presentation to T cells. These data suggest that the ability of Ii to enhance antigen presentation is not limited to Golgi apparatus-endosomal sorting and raise the possibility that endocytosed class II can form immunogenic complexes with newly processed antigen.
Developmental regulation of a mucinlike glycoprotein selectively expressed on natural killer cells.
Authors: Vivier E , Sorrell J M , Ackerly M , Robertson M J , Rasmussen R A , Levine H , Anderson P
Published: June 2004

Natural killer (NK) cells are CD3:TCR-, CD16+, CD56+ large granular lymphocytes capable of recognizing and eliminating a variety of virus-infected, malignant, and antibody-coated target cells. Two functionally distinct populations of peripheral blood NK cells can be differentiated by their surface expression of an isoform of the neural cell adhesion molecule (CD56). CD56bright NK cells have the attributes of an undifferentiated cell, in that they proliferate in response to exogenous cytokines, but exert poor cytolytic activity. CD56dim NK cells have the attributes of a more differentiated cell, in that they proliferate poorly in response to exogenous cytokines, but are potent cytolytic effector cells. Here we describe the molecular characterization of a NK cell restricted epitope (PEN5) that is selectively expressed on the functionally differentiated CD56dim NK cells. PEN5+ NK cells proliferate poorly in response to interleukin 2 (IL-2), but are potent cytolytic effectors, whereas PEN5- NK cells proliferate in response to IL-2, but are poor cytolytic effectors. Biochemical and immunochemical analyses reveal the PEN5 epitope to be an unusual sulfated poly-N-lactosamine carbohydrate related to keratan sulfate glycosaminoglycans. Immunoprecipitates prepared using a monoclonal antibody reactive with PEN5 include two polydisperse membrane-bound glycoproteins, PEN5 alpha (120-170 kD) and PEN5 beta (210-245 kD). Enzymatic deglycosylation reduces the apparent molecular weight of both PEN5 isoforms by 80-90%, and classifies PEN5 beta as a mucinlike glycoprotein. The surface expression of the PEN5 epitope is downmodulated by stimuli that induce NK cell proliferation, and it is absent from leukemic NK cells of patients with granular lymphocyte proliferative disorder. Taken together, these results indicate that PEN5 is a developmentally regulated poly-N-lactosamine epitope associated with a mucin-type glycoprotein, whose expression is restricted to the population of nonproliferative NK cells fully committed to cytolytic effector function.
The related FLT4, FLT1, and KDR receptor tyrosine kinases show distinct expression patterns in human fetal endothelial cells.
Authors: Kaipainen A , Korhonen J , Pajusola K , Aprelikova O , Persico M G , Terman B I , Alitalo K
Published: June 2004

The growth factor receptors expressed on endothelial cells are of special interest because of their potential to program endothelial cell growth and differentiation during development and neovascularization in various pathological states, such as wound healing and angiogenesis associated with tumorigenesis. Vascular endothelial growth factor ([VEGF] also known as vascular permeability factor) is a potent mitogen and permeability factor, which has been suggested to play a role in embryonic and tumor angiogenesis. The newly cloned FLT4 receptor tyrosine kinase gene encodes a protein related to the VEGF receptors FLT1 and KDR/FLK-1. We have here studied the expression of FLT4 and the other two members of this receptor family in human fetal tissues by Northern and in situ hybridization. These results were also compared with the sites of expression of VEGF and the related placenta growth factor (PlGF). Our results reveal FLT4 mRNA expression in vascular endothelial cells in developing vessels of several organs. A comparison of FLT4, FLT1 and KDR/FLK-1 receptor mRNA signals shows overlapping, but distinct expression patterns in the tissues studied. Certain endothelia lack one or two of the three receptor mRNAs. These data suggest that the receptor tyrosine kinases encoded by the FLT gene family may have distinct functions in the regulation of the growth/differentiation of blood vessels.
Identification of a dominant epitope of glutamic acid decarboxylase (GAD-65) recognized by autoantibodies in stiff-man syndrome.
Authors: Butler M H , Solimena M , Dirkx R , Hayday A , De Camilli P
Published: June 2004

Glutamic acid decarboxylase (GAD) is the enzyme that synthesizes the neurotransmitter gamma-aminobutyric acid (GABA) in neurons and in pancreatic beta cells. It is a major target of autoimmunity in Stiff-Man syndrome (SMS), a rare neurological disease, and in insulin-dependent diabetes mellitus. The two GAD isoforms, GAD-65 and GAD-67, are the products of two different genes. GAD-67 and GAD-65 are very similar to each other in amino acid sequence and differ substantially only at their NH2-terminal region. We have investigated the reactivity of autoantibodies of 30 Stiff-Man syndrome patients to GAD. All patient sera contained antibodies that recognize strongly GAD-65, but also GAD-67, when tested by immunoprecipitation on brain extracts and by immunoprecipitation or immunocytochemistry on cells transfected with either the GAD-65 or the GAD-67 gene. When tested by Western blotting, all patient sera selectively recognized GAD-65. Western blot analysis of deletion mutants of GAD-65 demonstrated that autoantibodies are directed predominantly against two regions of the GAD-65 molecule. All SMS sera strongly recognized a fragment contained between amino acid 475 and the COOH terminus (amino acid 585). Within this region, amino acids 475-484 and 571-585 were required for reactivity. The requirement of these two discontinuous segments implies that the epitope is influenced by conformation. This reactivity is similar to that displayed by the monoclonal antibody GAD 6, suggesting the presence of a single immunodominant epitope (SMS-E1) in this region of GAD-65. In addition, most SMS sera recognized at least one epitope (SMS-E2) in the NH2-terminal domain of GAD-65 (amino acids 1-95). The demonstration in SMS patients of a strikingly homogeneous humoral autoimmune response against GAD and the identification of dominant autoreactive target regions may help to elucidate the molecular mechanisms of GAD processing and presentation involved in GAD autoimmunity. Moreover, the reactivity reported here of GAD autoantibodies in SMS partially differs from the reactivity of GAD autoantibodies in insulin-dependent diabetes mellitus, suggesting a link between the pattern of humoral autoimmunity and the clinical condition.
The importance of nef in the induction of human immunodeficiency virus type 1 replication from primary quiescent CD4 lymphocytes.
Authors: Spina C A , Kwoh T J , Chowers M Y , Guatelli J C , Richman D D
Published: June 2004

The viral regulatory gene, nef, is unique to the human immunodeficiency viruses (HIV) and their related primate lentiviruses. Expression of the nef gene has been shown to be essential to the maintenance of high levels of virus replication and the development of pathogenesis in the animal model of simian immunodeficiency virus (SIV) infection. In contrast to this in vivo model, the use of standard T cell culture systems to study nef function in vitro has produced a spectrum of contradictory results, and has failed to demonstrate a significant positive influence of nef on viral life cycle. We have developed a cell model to study regulation of HIV-1 replication that we believe reflects more accurately virus-cell interactions as they occur in vivo. Our experimental system used acute virus infection of purified, quiescent CD4 lymphocytes and subsequent induction of viral replication through T cell activation. With this cell model, NL4-3 virus clones with open and mutated nef reading frames were compared for replication competence. The clones with nef mutations showed reproducible and significant reductions in both rates of growth and maximal titers achieved. The degree of reduced replication was dependent on initial virus inoculum and the timing of T cell activation. The influence of nef was highly significant for induction of virus replication from a latent state within resting CD4 cells. Its effect was less apparent for virus infection of fully proliferating CD4 cells. This study demonstrates that nef confers a positive growth advantage to HIV-1 that becomes readily discernable in the primary cell setting of virus induction through T cell activation. The experimental cell model, which we describe here, provides not only a means to study nef function in vitro, but also provides important clues to the function of nef in HIV infection in vivo.
Reduced life span of anergic self-reactive B cells in a double-transgenic model.
Authors: Fulcher D A , Basten A
Published: June 2004

The life span of anergic self-reactive B cells was determined by 5-bromo-2'-deoxyuridine (BrdU) loading of tolerant double-transgenic (Dbl-Tg) mice produced by mating hen egg lysozyme (HEL)-transgenic mice with the corresponding immunoglobulin-transgenic (Ig-Tg) mice, the B cells of which express anti-HEL IgM and IgD. B cells from Dbl-Tg mice, despite being exposed to soluble antigen throughout their development, are not deleted, but persist in an anergic state. As a prelude to studying the life span of these anergic B cells, BrdU was administered to nontransgenic mice; B cells from the bone marrow, spleen, and lymph nodes displayed distinct kinetic profiles based on reciprocal expression of the B220 isoform of CD45 and heat-stable antigen (HSA). Thus, immature B220lo/HSAhi B cells incorporated BrdU rapidly suggesting recent generation from dividing precursors, whereas uptake by B cells expressing the mature B220hi/HSAlo phenotype was significantly slower, consistent with a longer life span. Such gating allowed analysis to be directed at the stable mature B cell population in transgenic mice. Comparison of BrdU uptake in Ig- and Dbl-Tg mice indicated that B cells from Dbl-Tg mice were renewed at a much higher rate (50% renewal times of 0.64 vs. 3.4 wk for total B cells, and 1.2 vs. 5.0 wk for mature B200hi/HSAlo cells from Dbl- and Ig-transgenic mice, respectively). This difference was even more marked when analysis in Dbl-Tg mice was restricted to HEL-binding cells, which had a 50% renewal time of 3-4 d compared with 4-5 wk for non-HEL-binding B cells. While the proportion of B cells in cell cycle, and the rate of entry of newly generated B cells into the spleen of Ig- and Dbl-Tg mice, were similar, B cell numbers were reduced in Dbl-Tg mice. It was therefore concluded that anergic B cells have a markedly decreased life span in the periphery. According to studies in radiation chimeras produced by reconstituting HEL-transgenic recipients expressing different serum levels of antigen with Ig-Tg bone marrow, the reduced life span of anergic B cells was associated with the anergic state per se, the serum concentration of HEL being important only in attaining the critical threshold necessary for tolerance induction. B cells rendered tolerant by exposure to soluble self-antigen therefore survive for a relatively short period in an anergic state once they have reached peripheral lymphoid tissue and fail to enter the long-lived compartment.(ABSTRACT TRUNCATED AT 400 WORDS)
Development of the airway intraepithelial dendritic cell network in the rat from class II major histocompatibility (Ia)-negative precursors: differential regulation of Ia expression at different levels of the respiratory tract.
Authors: Nelson D J , McMenamin C , McWilliam A S , Brenan M , Holt P G
Published: June 2004

The relative inefficiency of respiratory mucosal immune function during infancy is generally attributed to the immaturity of the neonatal T cell system. However, immune competence in the adult lung has recently been shown to be closely linked to the functional capacity of local networks of intraepithelial dendritic cells (DC). This study examines the density and distribution of these DC throughout the neonatal respiratory tract in rats, focusing particularly on microenvironmental regulation of their class II major histocompatibility complex (MHC) (Ia) expression. In animals housed under dust-controlled conditions, airway epithelial and alveolar Ia+ DC detectable by immunostaining with the monoclonal antibody (mAb) Ox6 are usually not seen until day 2-3 after birth, and adult-equivalent staining patterns are not observed until after weaning. In contrast, the mAb Ox62 detects large numbers of DC in fetal, infant, and adult rat airway epithelium. Costaining of these Ox62+ DC with Ox6 is rare in the neonate and increases progressively throughout infancy, and by weaning Ia+ DC comprised, on average, 65% of the overall intraepithelial DC population. In infant rats, Ia+ DC are observed first at the base of the nasal turbinates, sites of maximum exposure to inhaled particulates, suggesting that their maturation is driven in part by inflammatory stimuli. Consistent with this suggestion, densitometric analysis of Ia staining intensity of individual DC demonstrates that by 2-3 d after birth, Ia expression by nasal epithelial DC was comparable with that of Iahigh epidermal Langerhans cells in adjacent facial skin, at a time when expression by tracheal epithelial DC was 7-10-fold lower. Additionally, the rate of postnatal appearance of Iahigh DC in the airway epithelium was increased by administration of interferon gamma, and decreased by exposure of infant rats to aerosolized steroid. These findings collectively suggest that Ia expression by neonatal respiratory tract DC is locally controlled and can be upregulated by mediators that are produced within the lung and airway epithelium in response to inhalation of proinflammatory stimuli. It was also noted that Ialow neonatal airway DC expressed adult equivalent levels of class I MHC, which suggests differences in capacity to prime for CD8(+)-dependent versus CD4(+)-dependent immunity to inhaled pathogens, during the early postnatal period.
Lymphoma models for B cell activation and tolerance. X. Anti-mu-mediated growth arrest and apoptosis of murine B cell lymphomas is prevented by the stabilization of myc.
Authors: Fischer G , Kent S C , Joseph L , Green D R , Scott D W
Published: June 2004

Treatment of the WEHI-2131 or CH31 B cell lymphomas with anti-mu or transforming growth factor (TGF)-beta leads to growth inhibition and subsequent cell death via apoptosis. Since anti-mu stimulates a transient increase in c-myc and c-fos transcription in these lymphomas, we examined the role of these proteins in growth regulation using antisense oligonucleotides. Herein, we demonstrate that antisense oligonucleotides for c-myc prevent both anti-mu- and TGF-beta-mediated growth inhibition in the CH31 and WEHI-231 B cell lymphomas, whereas antisense c-fos has no effect. Furthermore, antisense c-myc promotes the appearance of phosphorylated retinoblastoma protein in the presence of anti-mu and prevents the progression to apoptosis as measured by propidium iodide staining. Northern and Western analyses show that c-myc message and the levels of multiple myc proteins were maintained in the presence of antisense c-myc, results indicating that myc species are critical for the continuation of proliferation and the prevention of apoptosis. These data implicate c-myc in the negative signaling pathway of both TGF-beta and anti-mu.
Membrane interactions influence the peptide binding behavior of DR1.
Authors: Sherman M A , Runnels H A , Moore J C , Stern L J , Jensen P E
Published: June 2004

We analyzed the binding of an influenza matrix protein-derived peptide, MAT(17-31), to cell surface and purified DR1. The pH dependence of peptide binding was dramatically influenced by the membrane environment. Cell surface binding was enhanced at low pH, with little or no binding detected at neutral pH and optimal binding at pH 4. By contrast, hydrogen ion concentration had minimal effect on peptide binding to purified DR1. Exposure to low pH in the absence of peptide did not affect the peptide binding capacity of cell-associated DR1. Purified DR1 was stable at low pH, excluding the possibility that enhanced binding was offset by a competing denaturation event at low pH. The striking effect of pH on peptide binding characteristic of cell surface DR1 was recovered after reconstitution of purified DR1 in B cell membranes by detergent dialysis. This behavior was partially recovered by reconstitution of full-length, but not truncated DR1 in vesicles containing purified lipid. Our results demonstrate that interactions involving membrane components influence the peptide-binding behavior of DR1.
Structural requirements for binding of an immunodominant myelin basic protein peptide to DR2 isotypes and for its recognition by human T cell clones.
Authors: Wucherpfennig K W , Sette A , Southwood S , Oseroff C , Matsui M , Strominger J L , Hafler D A
Published: June 2004

Immunodominant T cell epitopes of myelin basic protein (MBP) may be target antigens for major histocompatibility complex class II-restricted, autoreactive T cells in multiple sclerosis (MS). Since susceptibility to MS is associated with the DR2 haplotype, the binding and presentation of the immunodominant MBP(84-102) peptide by DR2 antigens were examined. The immunodominant MBP(84-102) peptide was found to bind with high affinity to DRB1*1501 and DRB5*0101 molecules of the disease-associated DR2 haplotype. Overlapping but distinct peptide segments were critical for binding to these molecules; hydrophobic residues (Val189 and Phe92) in the MBP(88-95) segment were critical for peptide binding to DRB1*1501 molecules, whereas hydrophobic and charged residues (Phe92, Lys93) in the MBP(89-101/102) sequence contributed to DRB5*0101 binding. The different registers for peptide binding made different peptide side chains available for interaction with the T cell receptor. Although the peptide was bound with high affinity by both DRB1 and DRB5 molecules, only DRB1 (DRB1*1501 and 1602) but not DRB5 molecules served as restriction elements for a panel of T cell clones generated from two MS patients suggesting that the complex of MBP(84-102) and DRB1 molecules is more immunogenic for MBP reactive T cells. The minimal MBP peptide epitope for several T cell clones and the residues important for binding to DRB1*1501 molecules and for T cell stimulation have been defined.
Rat T cell response to superantigens. I. V beta-restricted clonal deletion of rat T cells differentiating in rat-->mouse chimeras.
Authors: Surh C D , Gold D P , Wiley S , Wilson D B , Sprent J
Published: June 2004

T cells of mice display V beta-specific reactivity for a spectrum of mouse mammary tumor virus (Mtv) antigens; confrontation with these antigens during ontogeny causes substantial "holes" in the T cell repertoire. Since endogenous Mtv antigens are rare in other species, the question arises whether V beta-specific recognition of Mtv antigens is unique to mice. To examine this question, rat T cells were allowed to differentiate from stem cells in severe combined immunodeficiency (SCID) mice. These rat-->mouse xenochimeras were prepared under a variety of conditions. The results show that rat T cells are strongly reactive to mouse Mtv antigens, both in terms of tolerogenicity and immunogenicity. In fact, the V beta specificity of rat and mouse T cells for Mtv antigens is almost indistinguishable.
Distinct types of lung disease caused by functional subsets of antiviral T cells.
Authors: Alwan W H , Kozlowska W J , Openshaw P J
Published: June 2004

T cells appear to play a central role in viral bronchiolitis, but the effects of different functional and phenotypic subgroups of T cells have not been defined. To test the activities of T cells recognizing individual proteins of respiratory syncytial (RS) virus, virus-specific T cell lines were produced from mice primed by scarification with recombinant vaccinia viruses expressing the major surface glycoprotein (G), fusion protein (F) or second matrix (22K) protein of RS virus. As previously reported, the in vitro characteristics of these cells are predetermined by the choice of RS virus protein: 22K-specific cells are predominantly class I-restricted cytolytic CD8+ cells; F-specific cells, a mixture of cytolytic CD8+ cells and CD4+ cells with a T helper 1 cell (Th1) cytokine secretion profile, whereas those from G-sensitized mice are almost exclusively CD4+, with Th2 characteristics. Mice infected intranasally with RS virus showed mild illness and recovered fully, but developed respiratory distress after intravenous injections of T cells. Dose-for-dose, infected mice receiving G-specific cells suffered the most severe (sometimes fatal) illness, characterized by lung hemorrhage, pulmonary neutrophil recruitment (shock lung) and intense pulmonary eosinophilia. This disease was further enhanced by coinjection of 22K-specific cells, which alone caused mild shock lung without eosinophilia. F-specific cells caused minimal enhancement of pathology and had little or no effect on the disease caused by G-specific cells. Each cell line reduced lung virus titer and combined injections of G- and 22K-specific cells eliminated infection completely. The in vitro characteristics of these antiviral T cell lines therefore predict the pathological effects in vivo. Moreover, different forms of viral bronchiolitis can be caused by functionally distinct types of activated T cell.
Comparison of somatic mutation frequency among immunoglobulin genes.
Authors: Motoyama N , Miwa T , Suzuki Y , Okada H , Azuma T
Published: June 2004

We analyzed the frequency of somatic mutation in immunoglobulin genes from hybridomas that secrete anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) monoclonal antibodies. A high frequency of mutation (3.3-4.4%) was observed in both the rearranged VH186.2 and V lambda 1 genes, indicating that somatic mutation occurs with similar frequency in these genes in spite of the absence of an intron enhancer in lambda 1 chain genes. In contrast to the high frequency in J-C introns, only two nucleotide substitutions occurred at positions -462 and -555 in the 5' noncoding region in one of the lambda 1-chain genes and in none of the other three so far studied. Since a similar low frequency of somatic mutation was observed in the 5' noncoding region of inactive lambda 2-chain genes rendered inactive because of incorrect rearrangement, this region may not be a target or alternatively, may be protected from the mutator system. We observed a low frequency of nucleotide substitution in unrearranged V lambda 1 genes (approximately 1/15 that of rearranged genes). Together with previous results (Azuma T., N. Motoyama, L. Fields, and D. Loh, 1993. Int. Immunol. 5:121), these findings suggest that the 5' noncoding region, which contains the promoter element, provides a signal for the somatic mutator system and that rearrangement, which brings the promoter into close proximity to the enhancer element, should increase mutation efficiency.
Characterization of human immunodeficiency virus type 1-specific cytotoxic T lymphocyte clones isolated during acute seroconversion: recognition of autologous virus sequences within a conserved immunodominant epitope.
Authors: Safrit J T , Andrews C A , Zhu T , Ho D D , Koup R A
Published: June 2004

Virus-specific cytotoxic T lymphocytes (CTL) are involved in protective immunity to many virus infections. It has recently been shown that CTL are detectable early during primary infection with the primate lentiviruses, human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus. To better characterize the CTL response during acute HIV-1 infection, HIV-1-specific CTL clones were generated from two patients during symptomatic HIV-1 seroconversion. These CTL clones demonstrated specificity for env of HIV-1 and recognized sequences within gp41. Two human histocompatibility leukocyte antigen (HLA) A31-restricted clones from the same individual were found to have differing virus strain specificities. Both clones recognized the 11-amino acid peptide RLRDLLLIVTR from position 770-780 of gp41. A change from T to V at position 779 in this epitope abrogated lysis by one clone but not the other. A CTL clone from the other patient, restricted by a different class I HLA allele, recognized the nine-amino acid peptide HRLRDLLLI from position 769-777 of gp41. Of note, the peptide RLRDLLLIVTR has been shown by others to be presented to CTL by HLA-A3.1. Autologous virus sequences from seroconversion and up to 15 wk after presentation in these two patients were recognized by the CTL clones isolated during acute infection. None of the CTL clones recognized the MN strain of HIV-1, indicating the problems inherent in relying on a single virus strain in the development of a vaccine. These studies have identified an immunodominant and promiscuous area for the generation of CTL responses within gp41. This recognition of autologous virus sequences by the initial CTL response is consistent with the hypothesis that a single virus strain is transmitted to the seroconverter and that the CTL response is involved in the initial control of that virus. These studies indicate the importance of the CTL response to HIV-1 infection and have implications in the design of vaccines.
Separate metabolic pathways leading to DNA fragmentation and apoptotic chromatin condensation.
Authors: Sun D Y , Jiang S , Zheng L M , Ojcius D M , Young J D
Published: June 2004

Apoptosis is the predominant form of cell death observed in a variety of physiological and pathological conditions such as cancer involution, insect metamorphosis, the development of the immune and nervous systems, and embryogenesis. The typical nuclear changes taking place in apoptotic cells include extensive condensation of chromatin and internucleosomal DNA fragmentation into units of 200 base pairs. However, the mechanisms responsible for both chromatin condensation and DNA fragmentation have yet to be elucidated. In this study, micrococcal nuclease and the divalent cations, Ca2+ and Mg2+, were applied to isolated nuclei in an attempt to reconstitute in vitro the digestion of genomic DNA associated with apoptosis. Micrococcal nuclease was found to induce a typical pattern of DNA fragmentation, but did not give rise to chromatin condensation, whereas Ca2+/Mg2+ induced both chromatin condensation and DNA fragmentation in isolated mouse liver nuclei. When the endonuclease inhibitor ZnCl2 was used, the DNA fragmentation induced by Ca2+/Mg2+ in nuclei could be completely inhibited, but chromatin condensation still occurred. For comparison, intact liver cells were treated with valinomycin, a potassium ionophore, which gave rise to an atypical cell death, with chromatin condensation appearing without DNA fragmentation. Our results suggest that endonuclease activation in apoptosis is neither necessary nor sufficient to induce chromatin condensation, and that DNA fragmentation and chromatin condensation may be triggered through separate pathways during apoptosis.
Regulatory interactions between CD45RBhigh and CD45RBlow CD4+ T cells are important for the balance between protective and pathogenic cell-mediated immunity.
Authors: Powrie F , Correa-Oliveira R , Mauze S , Coffman R L
Published: June 2004

BALB/c mice infected with the intracellular protozoan Leishmania major mount a T helper cell 2 (Th2) response that fails to control growth of the parasite and results in the development of visceral leishmaniasis. Separation of CD4+ T cells into CD45RBhigh and CD45RBlow subsets showed that the L. major-specific Th2 cells were contained within the CD45RBlow population as these cells produced high levels of antigen-specific interleukin 4 (IL-4) in vitro and transferred a nonhealing response to L. major-infected C.B-17 scid mice. In contrast, the CD45RBhighCD4+ population contained L. major-reactive cells that produced interferon gamma (IFN-gamma) in vitro and transferred a healing Th1 response to L. major-infected C.B-17 scid mice. Transfer of the Th1 response by the CD45RBhigh population was inhibited by the CD45RBlow population by a mechanism that was dependent on IL-4. These data indicate that L. major-specific Th1 cells do develop in BALB/c mice, but their functional expression is actively inhibited by production of IL-4 by Th2 cells. In this response, the suppressed Th1 cells can be phenotypically distinguished from the suppressive Th2 cells by the level of expression of CD45RB. Although the CD45RBhigh population mediated a protective response to L. major, C.B-17 scid mice restored with this population developed a severe inflammatory response in the colon that was independent of L. major infection, and was prevented by cotransfer of the CD45RBlow population. The colitis appeared to be due to a dysregulated Th1 response as anti-IFN-gamma, but not anti-IL-4, prevented it. Taken together, the data show that the CD4+ T cell population identified by high level expression of the CD45RB antigen contains cells that mediate both protective and pathogenic Th1 responses and that the reciprocal CD45RBlow population can suppress both of these responses. Whether suppression of cell-mediated immunity is beneficial or not depends on the nature of the stimulus, being deleterious during L. major infection but crucial for control of potentially pathogenic inflammatory responses developing in the gut.
Human interleukin 10 induces naive surface immunoglobulin D+ (sIgD+) B cells to secrete IgG1 and IgG3.
Authors: Brière F , Servet-Delprat C , Bridon J M , Saint-Remy J M , Banchereau J
Published: June 2004

During antigen-induced immune responses, human B cells switch isotype from immunoglobulin M (IgM)-IgD to IgG1-4, IgA1-2, or IgE. In the human, no cytokines have yet been demonstrated to act as switch factors for IgG1, IgG2, and IgG3. In this paper, we report that in response to interleukin 10 (IL-10), anti-CD40 activated tonsillar surface IgD+ (sIgD+) B cells are induced to secrete large amounts of IgM, IgG1, and IgG3 but neither IgG2 nor IgG4. Cord blood purified B cells and lymphocytes from Hyper-IgM patients also produced IgG1 and IgG3 after culture with anti-CD40 and IL-10. In contrast, sIgD- isotype-committed B cells produce IgG1, IgG2, and IgG3 when activated through CD40 in the presence of IL-10. Thus, in addition to its growth-promoting and differentiating activities on human B cells, IL-10 may represent a switch factor for IgG1 and IgG3.