bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppressible and nonsuppressible autocrine mast cell tumors are distinguished by insertion of an endogenous retroviral element (IAP) into the interleukin 3 gene.
Authors: Hirsch H H , Nair A P , Moroni C
Published: June 2004

After v-H-ras expression, the interleukin 3 (IL-3)-dependent PB-3c mast cells progress in vivo to two different classes of IL-3 autocrine tumors. Class I tumors show a germline configuration of the IL-3 gene and represent more than 90% of tumors analyzed so far. Somatic cell fusion of class I tumor lines with the nontumorigenic parental PB-3c resulted in loss of oncogenic IL-3 expression by a posttranscriptional mechanism with concomitant tumor suppression. Class II tumors arise rarely and contain an insertion in one IL-3 allele. This alteration was linked to enhanced IL-3 gene transcription. For one tumor, the insertion was shown to be an endogenous retroviral element (intracisternal A-particle). Cell hybrids of class II tumors with PB-3c remained IL-3 independent, expressed IL-3, and formed tumors rapidly. These results suggest that the v-H-ras oncogene synergizes with a recessive and a dominant lesion in class I and II tumors, respectively, both of which lead to the autocrine production of IL-3.
An autoimmune disease with multiple molecular targets abrogated by the transgenic expression of a single autoantigen in the thymus.
Authors: Alderuccio F , Toh B H , Tan S S , Gleeson P A , van Driel I R
Published: June 2004

Many autoimmune diseases are characterized by autoantibody reactivities to multiple cellular antigens. Autoantigens are commonly defined as targets of the autoimmune B cell response, but the role, if any, of these autoantigens in T cell-mediated autoimmune diseases is generally unknown. Murine experimental autoimmune gastritis is a CD4+ T cell-mediated organ-specific autoimmune disease induced by neonatal thymectomy of BALB/c mice. The murine disease is similar to human autoimmune gastritis and pernicious anemia, and is characterized by parietal and chief cell loss, submucosal mononuclear cell infiltrates, and autoantibodies to the alpha and beta subunits of the gastric H/K ATPase. However, the specificity of T cells that cause the disease is not known. To examine the role of the H/K ATPase in this T cell-mediated disease, transgenic mice were generated that express the beta subunit of the H/K ATPase under the control of the major histocompatibility complex class II I-Ek alpha promoter. We show that transgenic expression of the gastric H/K ATPase beta subunit specifically prevents the onset of autoimmune gastritis after neonatal thymectomy. In addition, thymocyte transfer experiments suggest that tolerance of pathogenic autoreactive T cells is induced within the thymus of the transgenic mice. We conclude that the beta subunit of the gastric H/K ATPase is a major T cell target in autoimmune gastritis and that thymic expression of a single autoantigen can abrogate an autoimmune response to multiple autoantigens.
The significance of low bcl-2 expression by CD45RO T cells in normal individuals and patients with acute viral infections. The role of apoptosis in T cell memory.
Authors: Akbar A N , Borthwick N , Salmon M , Gombert W , Bofill M , Shamsadeen N , Pilling D , Pett S , Grundy J E , Janossy G
Published: June 2004

The bcl-2 gene product has been shown to prevent apoptotic cell death. We have now investigated the bcl-2 protein expression by resting and activated mature T cell populations. Freshly isolated CD45RO+ T cells within CD4+ and CD8+ subsets expressed significantly less bcl-2 than CD45RO- (CD45RA+) T cells (p < 0.001). When CD45RA+ T cells within both CD4+ and CD8+ subsets were activated in vitro, the transition to CD45RO phenotype was associated with a decrease in bcl-2 expression. Patients with acute viral infections such as infectious mononucleosis caused by Epstein-Barr virus infections or chickenpox, resulting from varicella zoster virus infection, had circulating populations of activated CD45RO+ T cells which also showed low bcl-2 expression. In these patients, a significant correlation was seen between low bcl-2 expression by activated T cells and their apoptosis in culture (r = 0.94, p < 0.001). These results suggest that the primary activation of T cells leads to the expansion of a population that is destined to perish unless rescued by some extrinsic event. Thus the suicide of CD45RO+ T cells could be prevented by the addition of interleukin 2 to the culture medium which resulted in a concomitant increase in the bcl-2 expression of these cells. Alternatively, apoptosis was also prevented by coculturing the activated T lymphocytes with fibroblasts, which maintained the viability of lymphoid cells in a restinglike state but with low bcl-2 expression. The paradox that the CD45RO+ population contains the primed/memory T cell pool yet expresses low bcl-2 and is susceptible to apoptosis can be reconciled by the observations that maintenance of T cell memory may be dependent on the continuous restimulation of T cells, which increases their bcl-2 expression. Furthermore, the propensity of CD45RO+ T cells to extravasate may facilitate encounter with fibroblast-like cells in tissue stroma and thus be an important additional factor which promotes the survival of selected primed/memory T cells in vivo.
Autoimmune disease in mice due to integration of an endogenous retrovirus in an apoptosis gene.
Authors: Wu J , Zhou T , He J , Mountz J D
Published: June 2004

The MRL-lpr/lpr mouse strain is a model of systemic autoimmune disease. In this model, intrinsic defects of intrathymic T cell development include defective deletion of self-reactive T cells and expression of endogenous retroviruses. Defective deletion of self-reactive T cells in the thymus has been proposed to be due to germline mutation in the Fas apoptosis gene. Using different fragments of a Fas cDNA probe, we determined that the lpr/lpr mutation is a 5.3-kb insertion of DNA within the second intron of the Fas gene. cDNA corresponding to this region was then derived from thymic RNA from MRL-lpr/lpr and MRL- +/+ mice using the polymerase chain reaction. All thymic RNA samples from MRL-lpr/lpr mice yielded a unique product that was 168 bp larger than that of MRL- +/+ mice. Complete sequence analysis indicated that this inserted sequence had 98% homology with a sequence from the 3' long terminal repeat of the early transposon (ETn). RNA analysis indicated higher expression of ETn RNA in the thymus of MRL-lpr/lpr than MRL- +/+ mice. The interdependence of ETn expression and abnormal Fas expression was then analyzed in a CD2-Fas transgenic mouse model in which a full-length murine Fas cDNA under the regulation of the CD2 promoter and enhancer was used to correct defective Fas expression in T cells of MRL-lpr/lpr mice. In these mice, reduced thymic ETn expression was observed, confirming that high ETn expression is related to abnormal Fas expression. These results establish a link between endogenous retrovirus expression, abnormal Fas expression, and autoimmune disease.
A complex of glycoproteins is associated with VpreB/lambda 5 surrogate light chain on the surface of mu heavy chain-negative early precursor B cell lines.
Authors: Karasuyama H , Rolink A , Melchers F
Published: June 2004

Monoclonal antibodies (mAbs) have been made specific for the pre-B cell-specific proteins VpreB and lambda 5 which together form the surrogate light (L) chain. mAbs specific for VpreB protein identified the 16-kD molecule associated on precursor B cell lines with lambda 5 protein as the product of the VpreB gene. Surrogate L chain was detectable even in the absence of mu heavy (H) chain on the surface of early precursor cell lines such as pro-B cell lines where all immunoglobulin (Ig) loci are in the germline configuration, as well as early pre-B cell lines where Ig H chain loci are DHJH rearranged in reading frame I or III, which does not allow the expression of a DHJHC mu protein. A complex of glycoproteins (200, 130, 105, and 65-35 kD) was identified as coprecipitated with the Vpreb/lamba 5 surrogate L chain in mu H chain-negative precursor B cell lines. The 130-kD protein was most strongly labeled with iodine and most consistently detected in noncovalent association with surrogate L chain. This protein turned out to be a N-linked glycoprotein with a 100-kD protein core and isoelectric point 5.8, indicating that it is distinct from CD43 and the BP-1/6C3 antigen. The surface deposition of the surrogate L chain in association with the newly identified glycoproteins suggests that the surrogate L chain may function as a receptor even before the association with mu H chain in early precursor B cells.
The tyrosinase gene codes for an antigen recognized by autologous cytolytic T lymphocytes on HLA-A2 melanomas.
Authors: Brichard V , Van Pel A , Wölfel T , Wölfel C , De Plaen E , Lethé B , Coulie P , Boon T
Published: June 2004

Lymphocytes of melanoma patients can be restimulated in vitro with autologous tumor cells to generate antitumor cytolytic T lymphocytes (CTL). Previous reports have indicated that, when such CTL are obtained from HLA-A2 melanoma patients, they often display broad reactivity on A2 melanoma cell lines. Such antitumor CTL clones, which appeared to recognize the same antigen, were isolated from two patients. We report here the cloning of a cDNA that directs the expression of the antigen recognized by these CTL. This cDNA corresponds to the transcript of the tyrosinase gene. The gene was found to be active in all tested melanoma samples and in most melanoma cell lines. Among normal cells, only melanocytes appear to express the gene. The tyrosinase antigen presented by HLA-A2 may therefore constitute a useful target for specific immunotherapy of melanoma. But possible adverse effects of antityrosinase immunization, such as the destruction of normal melanocytes and its consequences, will have to be examined before clinical pilot studies can be undertaken.
CD44 is necessary for optimal contact allergic responses but is not required for normal leukocyte extravasation.
Authors: Camp R L , Scheynius A , Johansson C , Puré E
Published: June 2004

The in vivo administration of certain monoclonal antibodies (mAbs) against the adhesion receptor, CD44, into normal mice induces both a modulation of CD44 from the surface of peripheral lymphocytes, and a concomitant increase in the amount of soluble CD44 in the serum. CD44-negative lymphocytes isolated from anti-CD44-treated mice exhibit normal homing patterns upon adoptive transfer, and are capable of reexpressing CD44 upon activation. The treatment of haptensensitized mice with anti-CD44 mAb inhibits their ability to mount a cutaneous delayed-type hypersensitivity (DTH) response within the first 24 h after hapten challenge. This inhibition reflects a block in both the edema and leukocyte infiltration of the cutaneous site of DTH, whereas the extravasation and accumulation of leukocytes in the draining lymph nodes progress normally. After 72 h, the leukocytes that extravasate into the site of antigen challenge express CD44. These results indicate that CD44 is not necessary for normal leukocyte circulation but is required for leukocyte extravasation into an inflammatory site involving nonlymphoid tissue.
Phagocytosis of antigens by Langerhans cells in vitro.
Authors: Reis e Sousa C , Stahl P D , Austyn J M
Published: June 2004

Dendritic cells (DC) isolated from lymphoid tissues are generally thought to be nonphagocytic in culture. It has therefore been unclear how these cells could acquire particulate antigens such as microorganisms for initiation of primary immune responses. Lymphoid DC derive in part from cells that have migrated from nonlymphoid tissues, such as Langerhans cells (LC) of skin. The ability of LC to internalize a variety of particles was studied by electron, ultraviolet, phase, and differential interference contrast microscopy, and by two-color flow cytometry. Freshly isolated LC in epidermal cell suspensions phagocytosed the yeast cell wall derivative zymosan, intact Saccharomyces cerevisiae, representatives of two genera of Gram-positive bacteria, Corynebacterium parvum and Staphylococcus aureus, as well as 0.5-3.5-microns latex microspheres. During maturation in culture, the phagocytic activity of these cells was markedly reduced. Likewise, freshly isolated splenic DC were more phagocytic than cultured DC for two types of particle examined, zymosan and latex beads. Unlike macrophages, LC did not bind or internalize sheep erythrocytes before or after opsonization with immunoglobulin G or complement, and did not internalize colloidal carbon. The receptors mediating zymosan uptake by LC were examined. For this particle, C57BL/6 LC were considerably more phagocytic than BALB/c LC and exhibited a reproducible increase in phagocytic activity after 6 h of culture followed by a decline, whereas this initial rise did not occur for BALB/c LC. These differential kinetics of uptake were reflected in the pattern of zymosan binding at 4 degrees C, and endocytosis of the soluble tracer fluorescein isothiocyanate-mannose-bovine serum albumin at 37 degrees C. Zymosan uptake by LC from both strains of mice was inhibited in the presence of mannan or beta-glucan, although to different extents, but not by antibodies specific for CR3 (CD11b/CD18). These data indicate that zymosan uptake by LC can be mediated by a mannose/beta-glucan receptor(s) that is differentially expressed in the two strains of mice and that is downregulated during maturation of LC in culture.
Natural killer cells are a source of interferon gamma that drives differentiation of CD4+ T cell subsets and induces early resistance to Leishmania major in mice.
Authors: Scharton T M , Scott P
Published: June 2004

Infection of mice with the protozoan Leishmania major provides an excellent model to define the factors involved in T helper (Th) subset development, since Th1 cells confer protection in resistant strains of mice, whereas Th2 cells are associated with the fatal outcome of susceptible mice. We previously found that interferon gamma (IFN-gamma) was required for Th1 cell development after infection of mice with L. major. In this report, we evaluate the contribution of natural killer (NK) cells to IFN-gamma levels early in L. major infection. NK cell activity was higher in resistant C3H/HeN mice than in susceptible BALB/c mice during the first week of infection, and removal of NK cells significantly decreased IFN-gamma levels and promoted interleukin 4 (IL-4) production in both the draining lymph nodes and spleen. IFN-gamma production by NK cells required the presence of CD4+ T cells or IL-2, but not CD8+ T cells. Enhanced disease, as measured by parasite numbers and lesion development, was observed in NK cell-depleted mice. Furthermore, a comparison of the NK cell response and the subsequent parasite burden in several inbred strains of mice demonstrated that NK cells mediate early resistance to L. major. Together, these data indicate that the stimulation of NK cells, through the production of IFN-gamma, plays an important role in initiating Th1 cell differentiation in leishmaniasis and in controlling early resistance to L. major.
Platelet activation by C1q results in the induction of alpha IIb/beta 3 integrins (GPIIb-IIIa) and the expression of P-selectin and procoagulant activity.
Authors: Peerschke E I , Reid K B , Ghebrehiwet B
Published: June 2004

C1q receptors (C1qR) have been identified on a variety of somatic and cultured cells including peripheral blood platelets. Since platelets are likely to encounter both circulating C1q multimers and C1q associated with the extracellular matrix after complement activation by the classical pathway, the present study was designed to assess the effect of fluid phase and immobilized C1q on platelet function. Platelet adhesion to C1q-coated surfaces was accompanied by the induction of fibrinogen receptors. Scatchard analysis of fibrinogen binding to adherent platelets revealed the binding of approximately 10,000 molecules of fibrinogen per platelet with a Kd of 0.1 +/- 0.03 microM (mean +/- SD, n = 4). Furthermore, fluid phase C1q multimers were noted to aggregate platelets at doses > 5 micrograms/ml. This aggregation was preceded by a rise in inositol-1,4,5-trisphosphate (IP3) (6.9 +/- 2.4 pmoles/10(9) platelets at 15 s, n = 4), and activation of GPIIb-IIIa complexes supporting fibrinogen binding. Platelet aggregation in response to C1q multimers was accompanied by the aspirin-inhibitable release of granule contents and P-selectin (CD62) expression. Platelet aggregation was inhibited by the collagenous domain of C1q (c-Clq) and a monoclonal antibody directed against C1q receptors, suggesting the direct involvement of the 67-kD platelet C1qR. Antibodies against the very late antigen 2 or CD36 collagen receptors were without effect. Platelet exposure to C1q multimers was also accompanied by the expression of procoagulant activity, as demonstrated by the dose-dependent shortening of the kaolin recalcification time of normal plasma from 108 +/- 12 s in the presence of unstimulated platelets to 62 +/- 14 s in the presence of platelets that had been preincubated (5 min, 37 degrees C) with 100 micrograms/ml multimeric C1q (n = 3). These data suggest that platelet interactions with C1q multimers or immobilized C1q, resulting in the activation of GPIIb-IIIa fibrinogen binding sites and the expression of P-selectin as well as platelet procoagulant activity, are likely to contribute to thrombotic events associated with complement activation and inflammation.
P58 molecules as putative receptors for major histocompatibility complex (MHC) class I molecules in human natural killer (NK) cells. Anti-p58 antibodies reconstitute lysis of MHC class I-protected cells in NK clones displaying different specificities.
Authors: Moretta A , Vitale M , Bottino C , Orengo A M , Morelli L , Augugliaro R , Barbaresi M , Ciccone E , Moretta L
Published: June 2004

Human CD3-16+56+ natural killer (NK) cells have been shown to display a clonally distributed ability to recognize major histocompatibility complex (MHC) class I alleles. Opposite to T lymphocytes, in NK cells, specific recognition of MHC class I molecules appears to induce inhibition of cytolytic activity and, thus, to protect target cells. Since a precise correlation has been established between the expression of the NK-specific GL183 and EB6 surface molecules (belonging to the novel p58 molecular family) and the specificity of NK clones, we analyzed whether p58 molecules could function as receptors for MHC in human NK cells. NK clones displaying the previously defined "specificity 2" and characterized by the GL183+EB6+ phenotype, specifically recognize the Cw3 allele and thus fail to lyse the Fc gamma R+ P815 target cells transfected with Cw3. On the other hand, NK clones displaying "specificity 1" and expressing the GL183-EB6+ phenotype failed to lyse Cw4+ target cells. Addition of the F(ab')2 fragments of either GL183 or EB6 mAb as well as the XA141 mAb of IgM isotype (specific for the EB6 molecules) completely restored the lysis of Cw3-transfected P815 cells by the Cw3-specific NK clones EX2 and EX4. Similarly, both the entire EB6 mAb, its F(ab')2 fragment and the XA141 mAb reconstituted the lysis of C1R, a Fc gamma R- target cell expressing Cw4 as the only serologically detected class I antigen. Thus, it appears that masking of different members of p58 molecules prevents recognition of "protective" MHC class I alleles and thus the delivering of inhibitory signals. Further support to the concept that p58 molecules represent a NK receptor delivering a negative signal was provided by experiments in which the entire anti-p58 mAbs (of IgG isotype) could inhibit the lysis of unprotected Fc gamma R+ P815 target cells, thus mimicking the inhibitory effect of MHC class I molecules.
Multiple rearrangements in T cell receptor alpha chain genes maximize the production of useful thymocytes.
Authors: Petrie H T , Livak F , Schatz D G , Strasser A , Crispe I N , Shortman K
Published: June 2004

Peripheral T lymphocytes each express surface T cell receptor (TCR) alpha and beta chains of a single specificity. These are produced after random somatic rearrangements in TCR alpha and beta germline genes. Published model systems using mice expressing TCR alpha and/or beta chain transgenes have shown that allelic exclusion occurs conventionally for TCR-beta. TCR alpha chain expression, however, appears to be less strictly regulated, as endogenous TCR alpha chains are often found in association with transgenic TCR beta chains in TCR alpha/beta transgenic mice. This finding, coupled with the unique structure of the TCR alpha locus, has led to the suggestion that unlike TCR beta and immunoglobulin heavy chain genes, TCR alpha genes may make multiple rearrangements on each chromosome. In the current study, we demonstrate that the majority of TCR-, noncycling thymocytes spontaneously acquire surface expression of CD3/TCR. Further, we show that cultured immature thymocytes originally expressing specific TCR alpha and beta chains may lose surface expression of the original TCR alpha, but not beta chains. These data provide evidence that not only must multiple rearrangements occur, but that TCR alpha gene rearrangement continues even after surface expression of a TCR alpha/beta heterodimer, apparently until the recombination process is halted by positive selection, or the cell dies. Sequential rearrangement of TCR alpha chain genes facilitates enhanced production of useful thymocytes, by increasing the frequency of production of both in-frame rearrangements and positively selectable TCR alpha/beta heterodimers.
Protective effects of sialylated oligosaccharides in immune complex-induced acute lung injury.
Authors: Mulligan M S , Lowe J B , Larsen R D , Paulson J , Zheng Z L , DeFrees S , Maemura K , Fukuda M , Ward P A
Published: June 2004

Using sialyl Lewisx (SLX) oligosaccharides derived from fucosyl transferase-expressing cells or generated synthetically, the ability of these compounds to protect against acute lung damage after deposition of immunoglobulin (Ig)G or IgA immune complexes has been determined. The synthetic compounds were tetra- and pentasaccharide derivates of SLX as well as the nonfucosylated forms of SLX as controls. In the IgG immune complex model of lung injury, which is E-selectin dependent, SLX preparations provided dose-dependent protective effects, as assessed by changes in lung vascular permeability and hemorrhage. Protective effects were associated with diminished tissue accumulation of neutrophils in lungs (as assessed by myeloperoxidase). Morphological assessment revealed reduced physical contact of neutrophils with the pulmonary vascular endothelium and reduced tissue accumulation of neutrophils. In the model of IgA immune complex-induced lung injury, which does not involve participation of neutrophils and is independent of the requirement for E-selectin, SLX preparations were not protective. These data suggest that, in neutrophil-mediated and E-selectin-dependent lung injury, SLX preparations provide significant, protective effects against inflammatory vascular injury. The ability to achieve antiinflammatory outcomes in vivo with appropriate oligosaccharides suggests a new approach to the blocking of acute inflammatory responses.
Nitric oxide localized to spinal cords of mice with experimental allergic encephalomyelitis: an electron paramagnetic resonance study.
Authors: Lin R F , Lin T S , Tilton R G , Cross A H
Published: June 2004

Experimental allergic encephalomyelitis (EAE) is a demyelinating autoimmune disorder that can be induced in susceptible mice by T lymphocytes sensitized to central nervous system (CNS) myelin components and is a prime animal model for the human CNS demyelinating disorder, multiple sclerosis (MS). Although CNS inflammation in which T lymphocytes and activated macrophages are the predominant cell types is observed in mice with EAE and in humans with MS, the exact mechanisms underlying the CNS damage and demyelination are not understood. Nitric oxide (NO), a gaseous free radical, has recently been shown to be a cytolytic product of activated macrophages. Using electron paramagnetic resonance spectroscopy, the nitric oxide free radical complexed with iron-sulfur proteins has been identified in affected spinal cords of mice with EAE, concurrent with the diminution of iron-sulfur proteins. These results indicate NO may play a role in the disease process of EAE, and perhaps MS.
Interchangeable alpha chain cytoplasmic domains play a positive role in control of cell adhesion mediated by VLA-4, a beta 1 integrin.
Authors: Kassner P D , Hemler M E
Published: June 2004

Integrins can exist in a range of functional states, depending on the cell type and its state of activation. Although the mechanism that controls activity is unknown, it has been suggested that for some integrins, alpha chain cytoplasmic domains may exert either a negative effect or no effect on adhesion function. To address this issue for VLA-4 (an alpha 4 beta 1 heterodimer), we constructed an alpha 4 cytoplasmic deletion mutant and chimeric alpha chains composed of the extracellular domains of alpha 4 and the cytoplasmic domains of alpha 2, alpha 4, or alpha 5. Upon stable transfection of wild-type alpha 4, VLA-4 heterodimer was obtained that mediated (a) poor adhesion to CS1 peptide, fibronectin, or vascular cell adhesion molecule 1 (VCAM-1) (in K562 cells); (b) poor adhesion to CS1 peptide but moderate adhesion to VCAM-1 (in MIP101 cells); and (c) moderate adhesion to both CS1 peptide and VCAM-1 (in PMWK cells). Chimeric alpha 4 constructs and wild-type alpha 4 yielded similar results in these cell lines. In contrast, truncation of the alpha 4 cytoplasmic domain (after the conserved GFFKR motif) caused an almost complete loss of adhesive activity in all three cell lines. Thus, several interchangeable alpha chain cytoplasmic domains play a fundamentally positive role in determining the state of constitutive activity for VLA-4. The alpha chain cytoplasmic domain is also required for agonist-stimulated adhesion, since phorbol ester stimulated the cell adhesion mediated by wild-type and chimeric alpha chains, but not by the cytoplasmic deletion mutant. The inactivity of both wild-type VLA-4 (in K562 cells), and truncated VLA-4 (in all three cell lines) was overcome by the addition of a stimulatory anti-beta 1 monoclonal antibody. Thus, the alpha cytoplasmic domain-dependent cellular mechanism controlling both constitutive and agonist-stimulated VLA-4 activity could be bypassed by external manipulation of the integrin.
Structural features of human immunoglobulin G that determine isotype-specific differences in complement activation.
Authors: Tao M H , Smith R I , Morrison S L
Published: June 2004

Although very similar in sequence, the four subclasses of human immunoglobulin G (IgG) differ markedly in their ability to activate complement. Glu318-Lys320-Lys322 has been identified as a key binding motif for the first component of complement, C1q, and is present in all isotypes of Ig capable of activating complement. This motif, however, is present in all subclasses of human IgG, including those that show little (IgG2) or even no (IgG4) complement activity. Using point mutants of chimeric antibodies, we have identified specific residues responsible for the differing ability of the IgG subclasses to fix complement. In particular, we show that Ser at position 331 in gamma 4 is critical for determining the inability of that isotype to bind C1q and activate complement. Additionally, we provide further evidence that levels of C1q binding do not necessarily correlate with levels of complement activity, and that C1q binding alone is not sufficient for complement activation.
CD40 expression by human monocytes: regulation by cytokines and activation of monocytes by the ligand for CD40.
Authors: Alderson M R , Armitage R J , Tough T W , Strockbine L , Fanslow W C , Spriggs M K
Published: June 2004

CD40 is a member of the tumor necrosis factor (TNF) receptor family of cell surface proteins and was originally described as a B cell restricted antigen. Treatment of primary human monocytes with granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), or interferon gamma (IFN-gamma) resulted in the induction of CD40 mRNA and enhancement of cell surface protein expression. CD40 was found to mediate monocyte adhesion to cells expressing recombinant CD40 ligand. CD40 ligand-transfected cells provided a potent costimulus for monocyte TNF-alpha and IL-6 production in the presence of GM-CSF, IL-3, or IFN-gamma, and enhanced IL-8 production stimulated by GM-CSF or IL-3. In addition, CD40 ligand-transfected cells acting in the absence of a costimulus induced monocytes to become tumoricidal against a human melanoma cell target. Collectively, these data indicate that CD40 ligand is pleiotropic with potent biological activity on monocytes.
T cell receptor interaction with peptide/major histocompatibility complex (MHC) and superantigen/MHC ligands is dominated by antigen.
Authors: Ehrich E W , Devaux B , Rock E P , Jorgensen J L , Davis M M , Chien Y H
Published: June 2004

While recent evidence strongly suggests that the third complementarity determining regions (CDR3s) of T cell receptors (TCRs) directly contact antigenic peptides bound to major histocompatibility complex (MHC) molecules, the nature of other TCR contact(s) is less clear. Here we probe the extent to which different antigens can affect this interaction by comparing the responses of T cells bearing structurally related TCRs to cytochrome c peptides and staphylococcal enterotoxin A (SEA) presented by 13 mutant antigen-presenting cell (APC) lines. Each APC expresses a class II MHC molecule (I-Ek) with a single substitution of an amino acid residue predicted to be located on the MHC alpha helices and to point "up" towards the TCR. We find that very limited changes (even a single amino acid) in either a CDR3 loop of the TCR or in a contact residue of the antigenic peptide can have a profound effect on relatively distant TCR/MHC interactions. The extent of these effects can be as great as that observed between T cells bearing entirely different TCRs and recognizing different peptides. We also find that superantigen presentation entails a distinct mode of TCR/MHC interaction compared with peptide presentation. These data suggest that TCR/MHC contacts can be made in a variety of ways between the same TCR and MHC, with the final configuration apparently dominated by the antigen. These observations suggest a molecular basis for recent reports in which either peptide analogues or superantigens trigger distinct pathways of T cell activation.
The defect in Fas mRNA expression in MRL/lpr mice is associated with insertion of the retrotransposon, ETn.
Authors: Chu J L , Drappa J , Parnassa A , Elkon K B
Published: June 2004

Fas is a cell surface protein of the tumor necrosis factor receptor, nerve growth factor receptor, CD40 family, and is involved in the control of lymphocyte apoptosis. A mutation in the Fas gene in MRL/lpr mice results in massive lymphoproliferation (lpr) and accelerated autoimmunity. To further study the nature of this defect, Fas mRNA expression was evaluated by reverse transcriptase polymerase chain reaction as well as by Northern blotting. These studies revealed that the wild-type Fas message was produced at approximately 10-fold lower levels in the lpr compared with the ++ substrain of MRL mice. In addition to the wild-type transcript, lpr mice also synthesized chimeric transcripts containing an insertion of the early retrotransposon (ETn). Molecular cloning and nucleotide sequencing of a Fas-ETn chimeric cDNA suggested that the striking reduction in wild-type Fas mRNA levels and the presence of aberrant transcripts in MRL/lpr mice are most likely explained by the insertion of the ETn retrotransposon into an intron of the Fas gene and induction of alternative splicing involving the 5' ETn long terminal repeat.
Cell surface expression and function of an HLA class II molecule with class I domain configuration.
Authors: Olson R R , Reuter J J , Scalf K
Published: June 2004

Recombinant major histocompatibility complex (MHC) class II molecules were expressed with extracellular polypeptide domains reorganized to form heavy (H) and light (L) chains (alpha 1-beta 1-beta 2 and alpha 2) analogous to class I. Accurate protein folding and dimerization is demonstrated by the ability of this 3+1-DR1 construct to bind class II-restricted peptides and stimulate CD4+ T cells. Cell surface expression of a functional class II molecule consisting of H and L chains supports the validity of current class II models and affirms the evolutionary relatedness of class I/II. MHC functions that differ between class I/II may be influenced by domain configuration, and the use of domain-shifted constructs will allow examination of this possibility.
Interleukin 13 inhibits human immunodeficiency virus type 1 production in primary blood-derived human macrophages in vitro.
Authors: Montaner L J , Doyle A G , Collin M , Herbein G , Illei P , James W , Minty A , Caput D , Ferrara P , Gordon S
Published: June 2004

The mechanisms by which cellular immunity maintains the asymptomatic state after human immunodeficiency virus type 1 (HIV-1) infection are poorly understood. CD4+ T lymphocytes play a complex role in regulating anti-HIV effector pathways, including activation of macrophages, which are themselves implicated in clinical latency and pathogenesis of symptomatic acquired immune deficiency syndrome. We have found that a newly identified T helper type 2 lymphokine, interleukin 13 (IL-13), inhibits HIV-1ADA and Ba-L replication in primary tissue culture-derived macrophages but not in peripheral blood lymphocytes. Viral production in cells was measured by viral protein (p24) and reverse transcriptase levels, while entry was assessed by proviral DNA analysis at timed intervals after infection. Inhibition by IL-13 was dose and time dependent and not mediated through altered viral entry, reverse transcription, or viral release. IL-13 is therefore a candidate cytokine for the suppression of HIV infection within monocytes and macrophages in vivo.
Suppression of arthritis by an inhibitor of nitric oxide synthase.
Authors: McCartney-Francis N , Allen J B , Mizel D E , Albina J E , Xie Q W , Nathan C F , Wahl S M
Published: June 2004

Nitric oxide (NO), a toxic radical gas produced during the metabolism of L-arginine by NO synthase (NOS), has been implicated as a mediator of immune and inflammatory responses. A single injection of streptococcal cell wall fragments (SCW) induces the accumulation of inflammatory cells within the synovial tissue and a cell-mediated immune response that leads destructive lesions. We show here that NO production is elevated in the inflamed joints of SCW-treated rats. Administration of NG-monomethyl-L-arginine, an inhibitor of NOS, profoundly reduced the synovial inflammation and tissue damage as measured by an articular index and reflected in the histopathology. These studies implicate the NO pathway in the pathogenesis of an inflammatory arthritis and demonstrate the ability of a NOS inhibitor to modulate the disease.
Identification of an extracellular plasmin binding protein from nephritogenic streptococci.
Authors: Poon-King R , Bannan J , Viteri A , Cu G , Zabriskie J B
Published: June 2004

Examination of the extracellular products of nephritis(+) and nephritis(-) group A streptococci revealed the presence of a 46-kD protein secreted by nephritogenic strains that binds to human plasmin. Immunological data revealed that this protein, called nephritis plasmin binding protein (NPBP), is not related to group A streptokinase nor to a recently described streptococcal dehydrogenase protein. The binding of human plasmin to this protein can be blocked by epsilon-amino caproic acid, indicating the importance of lysine groups in the binding process. Mutanolysin extracts of cell walls from these nephritogenic strains probed with anti-NPBP antibody were negative for cell wall-bound NPBP. Serological data with acute poststreptococcal glomerulonephritis (APSGN) and acute rheumatic fever sera indicated that the protein reacts preferentially with APSGN sera. Amino acid sequence analysis and immunological reactivity suggest NPBP is the streptococcal pyrogenic exotoxin B precursor, also previously described as zymogen (streptococcal proteinase precursor). The secretion of both group A streptokinase and a secreted plasmin binding protein in the same nephritogenic strain raises an intriguing hypothesis of the mechanisms of action of this protein in APSGN.
Hck tyrosine kinase activity modulates tumor necrosis factor production by murine macrophages.
Authors: English B K , Ihle J N , Myracle A , Yi T
Published: June 2004

The hematopoietic cell kinase (hck) is a member of the src family of tyrosine kinases, and is primarily expressed in myeloid cells. Hck expression increases with terminal differentiation in both monocyte/macrophages and granulocytes and is further augmented during macrophage activation. Recent evidence has implicated src-related tyrosine kinases in critical signaling pathways in other hematopoietic lineages. Herein we demonstrate that manipulation of the level of hck expression in the murine macrophage cell line BAC1.2F5 alters the responsiveness of these cells to activation by bacterial lipopolysaccharide (LPS) but does not affect survival or proliferation. Overexpression of an activated mutant of hck in BAC1.2F5 cells augments tumor necrosis factor (TNF) production in response to LPS, whereas inhibition of endogenous hck expression, by antisense oligonucleotides, interferes with LPS-mediated TNF synthesis. Together, these observations suggest that hck is an important component of the signal transduction pathways in activated macrophages.
Human natural killer (NK) alloreactivity and its association with the major histocompatibility complex: ancestral haplotypes encode particular NK-defined haplotypes.
Authors: Christiansen F T , Witt C S , Ciccone E , Townend D , Pende D , Viale D , Abraham L J , Dawkins R L , Moretta L
Published: June 2004

As ancestral haplotypes of the major histocompatibility complex (MHC) appear to define identical MHC haplotypes in unrelated individuals, unrelated individuals sharing the same ancestral haplotype should also share the same NK-defined allospecificities that have recently been shown to map to the human MHC. To test this prediction, multiple cell lines from unrelated individuals sharing the same ancestral haplotypes were tested for the NK-defined allospecificities. It was found that cells sharing the same ancestral haplotypes do have the same NK-defined specificities. Furthermore, the NK-defined phenotype of cells that possess two different ancestral haplotypes can be predicted from the NK-defined phenotypes of unrelated cells that are homozygous for the ancestral haplotypes concerned. Although the group 1 and 2 NK-defined allospecificities can be explained to some extent by HLA-C alleles, evidence is presented that additional genes may modify the phenotype conferred by HLA-C.
IP-10, a -C-X-C- chemokine, elicits a potent thymus-dependent antitumor response in vivo.
Authors: Luster A D , Leder P
Published: June 2004

IP-10 is a member of the -C-X-C-chemokine superfamily of proinflammatory cytokines whose secretion is induced by interferon gamma (IFN-gamma) and lipopolysaccharide (LPS). To date no function has been described for IP-10. We have genetically engineered tumor cells to secrete high levels of murine IP-10 and demonstrate that while IP-10 has no effect on the growth of these tumor cells in culture, it elicits a powerful host-mediated antitumor effect in vivo. The IP-10 antitumor response is T lymphocyte dependent, non-cell autonomous, and appears to be mediated by the recruitment of an inflammatory infiltrate composed of lymphocytes, neutrophils, and monocytes. These results document an important biologic property of IP-10 and raise the possibility that some of the T cell-directed effects of IFN-gamma and LPS may be mediated by this chemokine.
Expression of a functional c-kit receptor on a subset of natural killer cells.
Authors: Matos M E , Schnier G S , Beecher M S , Ashman L K , William D E , Caligiuri M A
Published: June 2004

Natural killer (NK) cells are large granular lymphocytes thought to be important in the host's early immune response to viral infection and malignant transformation. NK cells proliferate and display enhanced cytotoxic activity in response to the T cell growth factor, interleukin 2 (IL-2). Stem cell factor or steel factor (SF) is the ligand for the c-kit receptor, and when combined with other hematopoietic growth factors, SF synergistically promotes the proliferation and differentiation of bone marrow stem cells. In the present study we show the c-kit receptor to be uniquely expressed on a subset of resting human NK cells (CD56bright) which constitutively expresses both the high affinity IL-2 receptor (IL-2R) and the intermediate affinity IL-2R. Other lymphocyte populations, including CD56dim NK cells, did not appear to express the c-kit receptor. Within the CD56bright NK cell subset, SF alone had no obvious effect on proliferation or cytotoxic activity. SF was shown to significantly augment the proliferative effect of IL-2, and caused a marked shift in the dose-response curve at IL-2 concentrations that selectively saturate the high affinity IL-2R. The potentiating effect of SF on NK cell proliferation was dependent on IL-2 binding to the high affinity IL-2R, and was blocked by a monoclonal antibody directed against the c-kit receptor. SF did not enhance proliferation at higher IL-2 concentrations that saturate the intermediate affinity IL-2R, nor did SF enhance IL-2-induced cytotoxic activity. Together, these data indicate that SF and IL-2 act synergistically to directly augment the proliferative capacity of a unique human NK cell subset constitutively expressing the high affinity IL-2R and the c-kit receptor. The implications of these findings on NK cell development and the host's early immune response to pathogen invasion are discussed.
Evidence for a bone marrow B cell transcribing malignant plasma cell VDJ joined to C mu sequence in immunoglobulin (IgG)- and IgA-secreting multiple myelomas.
Authors: Corradini P , Boccadoro M , Voena C , Pileri A
Published: June 2004

Multiple myeloma is a B cell malignancy characterized by the expansion of plasma cells producing monoclonal immunoglobulins (Ig). It has been regarded as a tumor arising at the B, pre-B lymphocyte, or even stem cell level. Precursor cells are presumed to proliferate and differentiate giving rise to the plasma cell clonal expansion. Antigenic features and specific Ig gene rearrangement shared by B lymphocytes and myeloma cells have supported this hypothesis. However, the existence of such a precursor is based upon indirect evidence and is still an open question. During differentiation, B cells rearrange variable (V) regions of Ig heavy chain genes, providing a specific marker of clonality. Using an anchor polymerase chain reaction assay, these rearranged regions from five patients with multiple myeloma were cloned and sequenced. The switch of the Ig constant (C) region was used to define the B cell differentiation stage: V regions are linked to C mu genes in pre-B and B lymphocytes (pre-switch B cells), but to C gamma or C alpha in post-switch B lymphocytes and plasma cells (post-switch B cells). Analysis of bone marrow cells at diagnosis revealed the presence of pre-switch B cells bearing plasma cell V regions still joined to the C mu gene. These cells were not identified in peripheral blood, where tumor post-switch B cells were detected. These pre-switch B cells may be regarded as potential myeloma cell precursors.
Interleukin 7 is produced by murine and human keratinocytes.
Authors: Heufler C , Topar G , Grasseger A , Stanzl U , Koch F , Romani N , Namen A E , Schuler G
Published: June 2004

Interleukin 7 (IL-7) was originally identified as a growth factor for B cell progenitors, and subsequently has been shown to exert proliferative effects on T cell progenitors and mature peripheral T cells as well. Constitutive IL-7 mRNA expression so far had been demonstrated in bone marrow stromal cell lines, thymus, spleen, and among nonlymphoid tissues in liver and kidney. Here we show that both murine and human keratinocytes express IL-7 mRNA and release IL-7 protein in biologically relevant amounts. The physiological or pathological relevance of keratinocyte-derived IL-7 is presently unknown. Our finding that keratinocytes can produce IL-7 in concert with reports that IL-7 is a growth factor for in vivo primed antigen-specific T cells, as well as for T lymphoma cells suggests, however, that keratinocyte-derived IL-7 is important in the pathogenesis of inflammatory skin diseases and cutaneous T cell lymphoma.
CD1d is involved in T cell-intestinal epithelial cell interactions.
Authors: Panja A , Blumberg R S , Balk S P , Mayer L
Published: June 2004

We assessed the role of the nonclassical class I molecule, CD1d, in the interaction between intestinal epithelial cells and T cells. In a mixed lymphocyte reaction (MLR) system where the stimulator cells were irradiated normal intestinal cells, the anti-CD1d monoclonal antibody (mAb) 3C11 inhibited T cell proliferation. In contrast, no inhibition was seen when mAb 3C11 was added to conventional MLR cultures (non T cell stimulators). Furthermore, no inhibition was seen when either airway epithelial cells were used as stimulator cells or lamina propria lymphocytes were used as responder cells. These latter two conditions along with a conventional MLR favor CD4+ T cell proliferation. However, we have previously shown that normal intestinal epithelial cells stimulate CD8+ T cells under similar culture conditions. Thus, CD1d expressed on intestinal epithelial cells may be an important ligand in CD8+ T cell-epithelial cell interactions.
Human interferon-inducible protein 10: expression and purification of recombinant protein demonstrate inhibition of early human hematopoietic progenitors.
Authors: Sarris A H , Broxmeyer H E , Wirthmueller U , Karasavvas N , Cooper S , Lu L , Krueger J , Ravetch J V
Published: June 2004

Human interferon-inducible protein 10 (IP-10), a member of the family of the small secreted proteins called intercrine cytokines or chemokines, is secreted by interferon gamma-stimulated T cells, monocytes, endothelial cells, and keratinocytes. We have begun to explore the biological properties of IP-10 by cloning and overexpression in baculovirus and in bacterial protein expression systems. A 9.9-kD protein was secreted by infected insect cells, which on sodium dodecyl sulfate-polyacrilamide gel electrophoresis comigrated with keratinocyte IP-10 and with f(22-98), a bacterial recombinant fragment lacking the signal sequence but containing all other residues of IP-10. All three reacted with antibodies recognizing residues 10-98 (alpha IP-10) and 77-98 of IP-10 (alpha 22), demonstrating that it is secreted by keratinocytes and insect cells after removal of the signal sequence but without proteolysis of the COOH-terminal end. Purified rIP-10 suppresses in vitro colony formation by early human bone marrow progenitor cells which need r-steel factor (rSLF) and rGM-CSF or rSLF and r-erythropoeitin (rEPO). The inhibition is dose dependent, is complete at concentrations > or = 50 ng/ml, is prevented by preincubation of rIP-10 with alpha IP-10, but not by alpha 22, and is seen with highly purified CD34+ cells, suggesting direct effect of rIP-10 on the progenitors. Combination of rIP-10 and other chemokines at inactive concentrations inhibited colony formation in a synergistic manner. rIP-10 did not affect colony formation in the absence of any growth factors or in the presence of rEPO or rGM-CSF but in absence of rSLF. The effects of IP-10 may be relevant to normal marrow function and might be harnessed to protect human hematopoietic progenitors from the cytotoxic effects of chemotherapy.