Human immune system development and survival of non-obese diabetic (NOD)-scid IL2rγ(null) (NSG) mice engrafted with human thymus and autologous haematopoietic stem cells.

Immunodeficient mice bearing targeted mutations in the IL2rg gene and engrafted with human immune systems are effective tools for the study of human haematopoiesis, immunity, infectious disease and transplantation biology. The most robust human immune model is generated by implantation of human fetal thymic and liver tissues in irradiated recipients followed by intravenous injection of autologous fetal liver haematopoietic stem cells [often referred to as the BLT (bone marrow, liver, thymus) model]. To evaluate the non-obese diabetic (NOD)-scid IL2rγ(null) (NSG)-BLT model, we have assessed various engraftment parameters and how these parameters influence the longevity of NSG-BLT mice. We observed that irradiation and subrenal capsule implantation of thymus/liver fragments was optimal for generating human immune systems. However, after 4 months, a high number of NSG-BLT mice develop a fatal graft-versus-host disease (GVHD)-like syndrome, which correlates with the activation of human T cells and increased levels of human immunoglobulin (Ig). Onset of GVHD was not delayed in NSG mice lacking murine major histocompatibility complex (MHC) classes I or II and was not associated with a loss of human regulatory T cells or absence of intrathymic cells of mouse origin (mouse CD45(+) ). Our findings demonstrate that NSG-BLT mice develop robust human immune systems, but that the experimental window for these mice may be limited by the development of GVHD-like pathological changes.

Human peripheral blood CD4 T cell-engrafted non-obese diabetic-scid IL2rγ(null) H2-Ab1 (tm1Gru) Tg (human leucocyte antigen D-related 4) mice: a mouse model of human allogeneic graft-versus-host disease.

Graft-versus-host disease (GVHD) is a life-threatening complication of human allogeneic haematopoietic stem cell transplantation. Non-obese diabetic (NOD)-scid IL2rγ(null) (NSG) mice injected with human peripheral blood mononuclear cells (PBMC) engraft at high levels and develop a robust xenogeneic (xeno)-GVHD, which reproduces many aspects of the clinical disease. Here we show that enriched and purified human CD4 T cells engraft readily in NSG mice and mediate xeno-GVHD, although with slower kinetics compared to injection of whole PBMC. Moreover, purified human CD4 T cells engraft but do not induce a GVHD in NSG mice that lack murine MHC class II (NSG-H2-Ab1(tm1Gru), NSG-Ab°), demonstrating the importance of murine major histocompatibility complex (MHC) class II in the CD4-mediated xeno-response. Injection of purified human CD4 T cells from a DR4-negative donor into a newly developed NSG mouse strain that expresses human leucocyte antigen D-related 4 (HLA-DR4) but not murine class II (NSG-Ab° DR4) induces an allogeneic GVHD characterized by weight loss, fur loss, infiltration of human cells in skin, lung and liver and a high level of mortality. The ability of human CD4 T cells to mediate an allo-GVHD in NSG-Ab° DR4 mice suggests that this model will be useful to investigate acute allo-GVHD pathogenesis and to evaluate human specific therapies.

Human peripheral blood leucocyte non-obese diabetic-severe combined immunodeficiency interleukin-2 receptor gamma chain gene mouse model of xenogeneic graft-versus-host-like disease and the role of host major histocompatibility complex.

Immunodeficient non-obese diabetic (NOD)-severe combined immune-deficient (scid) mice bearing a targeted mutation in the gene encoding the interleukin (IL)-2 receptor gamma chain gene (IL2rgamma(null)) engraft readily with human peripheral blood mononuclear cells (PBMC). Here, we report a robust model of xenogeneic graft-versus-host-like disease (GVHD) based on intravenous injection of human PBMC into 2 Gy conditioned NOD-scid IL2rgamma(null) mice. These mice develop xenogeneic GVHD consistently (100%) following injection of as few as 5 x 10(6) PBMC, regardless of the PBMC donor used. As in human disease, the development of xenogeneic GVHD is highly dependent on expression of host major histocompatibility complex class I and class II molecules and is associated with severely depressed haematopoiesis. Interrupting the tumour necrosis factor-alpha signalling cascade with etanercept, a therapeutic drug in clinical trials for the treatment of human GVHD, delays the onset and progression of disease. This model now provides the opportunity to investigate in vivo mechanisms of xenogeneic GVHD as well as to assess the efficacy of therapeutic agents rapidly.

Non-obese diabetic-recombination activating gene-1 (NOD-Rag1 null) interleukin (IL)-2 receptor common gamma chain (IL2r gamma null) null mice: a radioresistant model for human lymphohaematopoietic engraftment.

Immunodeficient hosts engrafted with human lymphohaematopoietic cells hold great promise as a preclinical bridge for understanding human haematopoiesis and immunity. We now describe a new immunodeficient radioresistant non-obese diabetic mice (NOD) stock based on targeted mutations in the recombination activating gene-1 (Rag1(null)) and interleukin (IL)-2 receptor common gamma chain (IL2rgamma(null)), and compare its ability to support lymphohaematopoietic cell engraftment with that achieved in radiosensitive NOD.CB17-Prkdc(scid) (NOD-Prkdc(scid)) IL2rgamma(null) mice. We observed that immunodeficient NOD-Rag1(null) IL2rgamma(null) mice tolerated much higher levels of irradiation conditioning than did NOD-Prkdc(scid) IL2rgamma(null) mice. High levels of human cord blood stem cell engraftment were observed in both stocks of irradiation-conditioned adult mice, leading to multi-lineage haematopoietic cell populations and a complete repertoire of human immune cells, including human T cells. Human peripheral blood mononuclear cells also engrafted at high levels in unconditioned adult mice of each stock. These data document that Rag1(null) and scid stocks of immunodeficient NOD mice harbouring the IL2rgamma(null) mutation support similar levels of human lymphohaematopoietic cell engraftment. NOD-Rag1(null) IL2rgamma(null) mice will be an important new model for human lymphohaematopoietic cell engraftment studies that require radioresistant hosts.

In vitro analysis of CD40-CD154 and CD28-CD80/86 interactions in the primary T-cell response to allogeneic "nonprofessional" antigen presenting cells.

BACKGROUND: Recently, several ligand interactions have been examined in detail as potential mediators of costimulatory signaling. The CD154/CD40 and CD28/B7 interactions have been highlighted as being among the more-significant contributors to proper activation of unprimed T lymphocytes. Human keratinocytes (HK) and human dermal fibroblasts (HF) are capable of expressing Class II HLA and CD40 antigens after interferon-gamma exposure, yet neither express significant levels of B7. HK and HF have been characterized as "nonprofessional" antigen presenting cells (APC) and their poor APC function has been partially attributed to deficient costimulatory activity. METHODS: In this study, we examined whether substituting for costimulatory signaling events through the addition of cross-linked monoclonal antibodies against the T-cell ligand/s (CD28 and/or CD154) could restore allostimulation. Mixed lymphocyte reactions were performed combining enriched human peripheral blood T cells and allogeneic HK or HF with or without stimulatory anti-CD28 and/or anti-CD154 antibodies. RESULTS: The results show that the addition of anti-CD28 alone permitted HF but not HK to present alloantigen effectively. In contrast, addition of both anti-CD154 and anti-CD28 was required to generate even a moderate proliferative response to allogeneic HK. Further, adding a monomorphic anti-HLA-DR antibody substantially inhibited these responses. Additional experiments suggest that signaling through CD40/CD154 directs HK to produce TGF-beta, which would adversely affect T-cell activation. CONCLUSIONS: The data presented highlight significant differences in signaling capacities for HK versus HF and provide evidence for a partial mechanism by which allogeneic human skin equivalents might be immunologically null upon engraftment.

Effects of immunoregulatory cytokines on the immunogenic potential of the cellular components of a bilayered living skin equivalent.

The purpose of this study was to determine if the immunocompatibility of an allogeneic living skin equivalent (LSE) would be affected by cytokines that would be potentially present at the wound site. Specifically, the ability of interleukin-1alpha (IL-1a), interleukin-6 (IL-6), or interleukin-12 (IL-12) to induce an allogeneic T cell response to "nonprofessional" antigen presenting cells (APC) was investigated in this series of experiments. Since cytokine concentrations at the wound site can vary greatly, recombinant IL-1a, IL-6, and IL-12 were used over a wide range of concentrations. These cytokines were either added directly to a mixed lymphocyte reaction (MLR) culture system or used to pretreat APC prior to use in the MLR culture. The addition of IL-12, IL-1alpha, or IL-6 into an MLR was examined as a possible means of providing the necessary costimulatory signal for functionally deficient APC, such as human keratinocytes (HK) and dermal fibroblasts (HF). While the results show that IL-1a and IL-12 can significantly augment a primary allogeneic response against appropriately equipped antigen presenting cells, the same was not true for HK or HF. Further experiments showed that pretreatment of HK, HF, or human umbilical vein endothelial cells (HUVEC) with Interferon-gamma (IFNgamma) and either IL-12, IL1alpha, or IL-6 had no significant affect on their ability to present alloantigen to immune-reactive T lymphocytes over IFNgamma-treatment alone. The data suggest that exposure of HK or HF to IL-1alpha, IL-6, or IL-12 in combination with IFNgamma does not provide the additional signal(s) required by these cells to effectively present alloantigen to unprimed T cells. The data suggests that exposure to these immunoregulatory cytokines in the wound bed would be unlikely to affect the immunocompatibility of the LSE.

Normal human keratinocytes inhibit the proliferation of unprimed T cells by TGFbeta and PGE2, but not IL-10.

Recent investigations in antigen processing suggest that many hematopoietic and nonhematopoietic cell types are capable of presenting alloantigen to T lymphocytes. However, the role of certain nonclassical antigen presenting cells is blurred by their apparent ability to down-regulate the immune response as well as activate immune cells, depending upon the microenvironment and the functional state of the responding cells. In this study we examine the ability of cultured allogeneic keratinocytes to inhibit the response of naive T cells to alloantigen or to anti-CD3. Our results demonstrate that as few as 6.25 x 10(3) keratinocytes significantly inhibited T cell proliferation in response to alloantigen as well as anti-CD3-mediated stimulation (49 and 54%, respectively). HK-mediated inhibition of T cell proliferation did not require cell contact, suggesting that inhibition is mediated by cytokines or other soluble factors. This was further supported by experiments demonstrating the inducibility of HK inhibitory activity in the presence of FCS, and the partial blockage of HK inhibitory activity through the addition of indomethacin or anti-TGFbeta antibody. Interestingly, the data suggest that IL-10, a known immunomodulatory cytokine, does not play a role in the inhibitory activity seen in this system. Taken together the results suggest that HK have the potential to regulate the response of T cells to antigen presented by other APC through the production of soluble factors.

Production and function of monocyte chemoattractant protein-1 and other beta-chemokines in murine glial cells.

Monocyte chemoattractant protein-1 (MCP-1), formerly termed JE, is a member of the beta-chemokine (C-C chemokine) family and has been shown to be produced by a variety of cell types. Recently, mRNA of JE/MCP-1 was detected in astrocytes during the acute phase of experimental allergic encephalomyelitis (EAE). In addition, supernatants collected from human cultured astrocytes have recently been found to be chemotactic for monocytes. However, chemokine production and function in glial cells has not been fully examined. Using a sandwich ELISA assay, we have now quantitated MCP-1 levels and assessed MCP-1 function on murine glial cells. Lipopolysaccharide (LPS), interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha induced MCP-1 secretion by astrocytes, but not microglia. In addition, pretreatment with interferon (IFN)-gamma significantly augmented MCP-1 production by either LPS or the above cytokines. In contrast, LPS preferentially induced production of another beta-chemokine, macrophage inflammatory protein-1 alpha (MIP-1 alpha) from microglial cells. MCP-1 induced chemotaxis of microglial cells and macrophages. Similarly, another beta-chemokine, TCA3, which is produced by encephalitogenic T lymphocytes, also induced chemotaxis of microglia and macrophages. These findings suggested that astrocytes and microglial cells differentially produce chemokines in the central nervous system, and that both astrocytes and T cells may facilitate recruitment and activation of microglial cells via production of beta-chemokines.

Susceptibility to tumors induced by polyoma virus is conferred by an endogenous mouse mammary tumor virus superantigen.

A dominant gene carried in certain inbred mouse strains confers susceptibility to tumors induced by polyoma virus. This gene, designated Pyvs, was defined in crosses between the highly susceptible C3H/BiDa strain and the highly resistant but H-2k-identical C57BR/cdJ strain. The resistance of C57BR/cdJ mice is overcome by irradiation, indicating an immunological basis. In F1 x C57BR/cdJ backcross mice, tumor susceptibility cosegregates with Mtv-7, a mouse mammary tumor provirus carried by the C3H/BiDa strain. This suggests that Pyvs might encode the Mtv-7 superantigen (SAG) and abrogate polyoma tumor immunosurveillance through elimination of T cells bearing specific V beta domains. DNA typing of 110 backcross mice showed no evidence of recombination between Pyvs and Mtv-7. Strongly biased usage of V beta 6 by polyoma virus-specific CD8+ cytotoxic T lymphocytes in C57BR/cdJ mice implicates T cells bearing this Mtv-7 SAG-reactive V beta domain as critical anti-polyoma tumor effector cells in vivo. These results indicate identity between Pyvs and Mtv-7 sag, and demonstrate a novel mechanism of inherited susceptibility to virus-induced tumors based on effects of an endogenous superantigen on the host's T cell repertoire.

Biologic activities of the beta-chemokine TCA3 on neutrophils and macrophages.

Previous in vivo and in vitro studies demonstrated that the murine beta-chemokine TCA3 is a chemoattractant for monocytes/macrophages and neutrophils. The ability of TCA3 to activate these cell populations is now evaluated. Treatment with 10 to 20 nM rTCA3 induced a respiratory burst with the production of superoxide and hydrogen peroxide in both casein-elicited and unstimulated neutrophil and macrophage populations. In addition, TCA3 treatment induced the production of reactive nitrogen intermediates, whereas stimulation with higher concentrations (100 nM) of TCA3 induced the exocytosis of lysozyme and elastase in the presence of cytochalasin B (7 micrograms/ml). Subnanomolar concentrations (100 pM) of TCA3 also caused integrin-mediated increases of adhesiveness to fibrinogen by neutrophils and macrophages. Increased adhesiveness is the most sensitive assay for TCA3 bioactivity. TCA3 treatment appears to involve signaling through a G-protein-linked receptor as Pertussis toxin abolished the TCA3-mediated increase of adhesiveness and the production of reactive nitrogen intermediates. The dose dependence of the TCA3-mediated activities indicate a coordinated inflammatory response mediated by varying concentrations of TCA3.

Biologic activities of the murine beta-chemokine TCA3.

The murine beta-chemokine TCA3 was purified to homogeneity. The biologic activities of the purified glycoprotein were evaluated in vivo and in vitro. Mice injected i.p. with 1- to 100-ng purified rTCA3 exhibited a rapid influx of neutrophils and macrophages. Increased numbers of neutrophils and monocytes were observed in peripheral blood within 15 min and peak at 45 min. After 45 min neutrophil and macrophage levels were increased in the peritoneal exudate with peak levels occurring at 2 h, followed by a subsequent decline by 24 h. Inflammatory responses were induced in a dose-dependent fashion. The in vivo inflammatory responses were mirrored by the pattern of TCA3-induced chemotaxis in vitro. Neutrophils and macrophages responded to similar concentrations of TCA3 (3 x 10(-9) to 10(-8) M). Lymph node cells responded to other chemokines but did not migrate to TCA3. We also demonstrated that rTCA3 stimulates a transient increase in cytoplasmic free calcium in monocytic cells through a PTX-sensitive pathway. Cross-desensitization studies indicate that TCA3 acts independently of other beta-chemokines (MIP-1 alpha and RANTES) and the alpha-chemokine IL-8. Furthermore, TCA3 does not induce a Ca2 lux in cells transfected with cDNA for the C-C CKR-1 chemokine receptor, supporting the conclusion that there are distinct receptors for TCA3.

Inhibition of in vivo tumor growth by the beta chemokine, TCA3.

TCA3 is a proinflammatory murine glycoprotein that shares structural features with cytokines of the beta chemokine family and is a chemoattractant for neutrophils and monocytes. To assess the in vivo functions of TCA3, the cDNA was expressed in two mouse myeloma cell lines. Although the transfected and control cells had similar growth rates in vitro, TCA3-expressing tumors demonstrated impaired growth in both normal and immunodeficient mice. Histologic evaluation of the injection sites demonstrated that TCA3 expression resulted in an early neutrophil and monocyte infiltrate accompanied by tumor necrosis. There was complete regression of the TCA3-transfected tumor in some immunocompetent syngeneic mice. The TCA3-transfected cells induced specific and long-lasting immunity in mice that showed complete tumor regression; these animals were resistant to challenge with nontransfected tumor cells. In contrast, priming with irradiated tumor cells provided little protection against challenge with nontransfected tumor, which indicates that TCA3 specifically augments tumor immunogenicity. Mixing TCA3-transfected cells with normal tumor cells causes retarded growth of the normal tumor cells provided the latter are injected into the same site. Furthermore, direct in situ injection of soluble rTCA3 early during the course of tumor implantation also inhibits tumor growth. The data suggest that TCA3 may perform two roles in tumor protection: it induces lymphocyte-independent antitumor activity and stimulates tumor-specific immunity. We speculate that TCA3 has natural adjuvant activities that result in augmented immune responses.

Serologic analysis of the mouse beta chemokine JE/monocyte chemoattractant protein-1.

Mouse monocyte chemoattractant protein-1 (MCP-1), previously termed JE, is a member of the beta chemokine gene family and a homologue of the human monocyte chemoattractant protein, MCP-1. Mouse rMCP-1 was used to immunize hamsters for the production of mAb. Seven mouse MCP-1-specific mAbs were characterized: two of these mAbs cross-reacted with the human MCP-1, as determined by ELISA. A sensitive and specific capture ELISA for MCP-1 quantitation, which allowed measurement of mouse MCP-1 levels in supernatants from cells stimulated with inflammatory agents, was developed. LPS-stimulated astrocytes produce the highest levels of MCP-1 (80 ng/ml); macrophages and mesangial cells produce lower levels of MCP-1 (2 to 14 ng/ml) after LPS stimulation. IL-1 and TNF-alpha stimulation also can induce low levels of MCP-1 production. Western blot analysis demonstrated that the predominant native form of mouse MCP-1 is a 30-kDa glycoprotein. Two mAbs (2H5 and 6C7) demonstrated dose-dependent neutralization of mouse MCP-1 chemotactic activity. To localize the epitope recognized by one of these neutralizing Abs, the mAb was used to bind a series of genetically engineered truncated variants of human MCP-1. The C-terminal residues 62 to 67 on human MCP-1 molecules seem to be critical to express the epitope recognized by the neutralizing 2H5 anti-MCP-1 mAb. However, multiple sites on the MCP-1 molecule seem to be critical for bioactivity. Thus, these Ab reagents provide a useful tool to explore the biology of the mouse MCP-1 beta chemokine.

Serologic analysis of a murine chemokine, TCA3.

The TCA3 gene encodes a proinflammatory cytokine related to IL-8 and MCP-1 (JE). TCA3 mRNA is produced by T cells in response to stimulation with Ag or Con A. Glycosylated and nonglycosylated forms of rTCA3 produced by transfected Chinese hamster ovary cells were purified. rTCA3 was used to immunize hamsters and produce mAb. Four mAb were characterized; each was specific for TCA3, failing to react with the closely related molecule MCP-1 (JE). Western blotting also demonstrated that all four mAb specifically recognize rTCA3, native TCA3 produced by activated mouse T cells, and the nonglycosylated TCA3 core protein. A sensitive and specific capture ELISA for TCA3 quantitation was developed, allowing measurement of TCA3 levels in the supernatants from activated murine splenocytes and T cell clones. In addition, two mAb demonstrated dose-dependent neutralization of TCA3 inflammatory activity. Thus, the results directly demonstrate that TCA3 is expressed in an activation-specific manner by mouse T cells. The data also provide characterization of mAb reagents specific for this new cytokine.

CTLA-4 and CD28 mRNA are coexpressed in most T cells after activation. Expression of CTLA-4 and CD28 mRNA does not correlate with the pattern of lymphokine production.

Ag-presenting cells provide at least two distinct signals for T cell activation. T cell receptor-dependent stimulation is provided by presentation of a specific peptide Ag in association with MHC molecules. In addition, APC also supply costimulatory signals required for T cell activation that are neither Ag- nor MHC restricted. One such costimulatory signal is mediated via the interaction of B7 on APC with the CD28 receptor on T cells. Recently, CTLA-4 has been shown to be a second B7 receptor on T cells. In the present report, we have examined the expression of CD28 and CTLA-4 on a panel of resting and activated normal T cell subsets and T cell clones by RNA blot analysis in an attempt to determine whether their expression defines reciprocal or overlapping subsets. CD28 was detected in resting T cells, whereas CTLA-4 was not. After stimulation with PHA and PMA for 24 h, CTLA-4 mRNA was expressed in both the CD4+ and CD8+ subsets as well as in CD28+ T cells. We examined 37 human and six murine T cell clones that had been previously characterized for their cytokine production. After activation, CTLA-4 and CD28 mRNA were coexpressed in 36 of 37 human T cell clones and all six murine T cell clones. These included T cells of CD4+8-, CD4-8+, and CD4-8- phenotypes as well as clones with Th1 and Th2 cytokine profiles. In contrast, CD28 but not CTLA-4 mRNA was detected in leukemic T cell lines and myelomas. CTLA-4 and B7 mRNA but not CD28 mRNA was detected in two long term HTLV-I-transformed T cell lines. These data demonstrate that CD28 and CTLA-4 mRNA are coexpressed in most activated T cells and T cell clones, providing evidence that they do not define reciprocal subsets. Moreover, they are consistent with the hypothesis that B7 transmits its signal through a single receptor, CD28, on resting T cells, and multiple receptors, CD28 and CTLA-4, on activated T cells.

Experimental allergic encephalomyelitis mediated by cloned T cells specific for a synthetic peptide of myelin proteolipid protein. Fine specificity and T cell receptor V beta usage.

Proteolipid protein (PLP) is the major protein of central nervous system myelin. SJL (H-2s) mice immunized with a synthetic peptide corresponding to PLP residues 139-151 develop acute EAE. In this study, 6 IAs-restricted, CD4+, TCR alpha beta-bearing T cell clones were derived from SJL/J mice after immunization with this synthetic peptide. The clones responded in in vitro proliferative assays to the whole PLP molecule and to PLP peptide 139-151, but not to irrelevant Ag. They also responded to truncated and overlapping forms of the peptide but five distinct reactivity patterns were observed using these peptides. A panel of anti-TCR V beta mAb and TCR V beta-specific cDNA probes were used to determine the TCR V beta usage of the clones. Five clones were found to use four different V beta (V beta 2, V beta 6, V beta 10, or V beta 17a), whereas the V beta on the sixth clone could not be identified. Five of the clones induced EAE of varying severity upon adoptive transfer into naive syngeneic mice or mice pretreated with irradiation and pertussis and one clone was nonencephalitogenic. The Ag-specific proliferative response of all but the nonencephalitogenic clone could be blocked by an anti-CD4 mAb. Thus, the clones showed differences in their fine specifity, TCR V beta usage, sensitivity to antibody blocking, and encephalitogenic potency. These data demonstrate that the T cell response to the encephalitogenic PLP peptide 139-151 is heterogeneous.

T cell recognition of Mlsc,x determinants.

Among a large number of cow insulin-specific T cell clones derived from both C57BL/10 and B10.A strains, several were found to react to non-MHC-linked gene products of a number of allogeneic strains. The stimulatory moiety for three of these clones correlates, in part, with expression of Mlsc, as defined by mouse strains C3H/HeJ and A/J. In addition, all three of these clones are stimulated by cells from strain PL/J, which has the poorly defined Mlsx allele. The data strongly suggest that Mlsx may, in fact, be Mlsc or is, at least, highly cross-reactive with Mlsc. Segregation analysis by using (B10.D2 X PL/J)F2 mice demonstrates that the Mlsx gene is genetically independent of the Mlsa linked Ly-9 marker on chromosome 1. Further studies with the use of these Mlsc,x-reactive clones reveal that they also recognize a gene product present in many mouse strains including DBA/2 which were previously phenotyped as Mlsa. However, testing of BxD recombinant inbred lines excludes Mlsa as being the stimulatory moiety. We therefore propose reclassification of the Mls phenotypes of several mouse strains based upon a two-locus model for Mls.

Synergy between stimulator cells in the induction of the anti-Mlsa response.

We have identified two types of clones responsive to Mls determinants. One type responded vigorously to purified B cells from mice bearing Mlsa-stimulatory determinants. The other type, including clone Ly1-N5, responded vigorously to unfractionated spleen cells, but failed to respond to B cells alone or to spleen-adherent cells (SAC) alone from the Mlsa-bearing mice. Synergy between two stimulator cell types, B cells and SAC, was required to induce the Mls response of clone Ly1-N5. The failure of clone Ly1-N5 to respond to Mlsa-bearing B cells was reversed by the addition of SAC taken from mice bearing the Mlsa allele or the non-stimulatory Mlsb allele. B cells were required to provide the Mlsa determinant. The Mls response of clone Ly1-N5 is restricted by class II determinants shared by the H-2b, H-2d and H-2k haplotypes, but not the H-2q haplotype. The optimal response of the clone was obtained by using B cells bearing both Mlsa and the permissive H-2 alloantigen. However, complementation was also observed between B cells bearing Mlsa and the non-permissive Iaq and SAC bearing the nonstimulatory Mlsb, but a permissive Ia epitope, resulting in activation of the clone. Clone Ly1-N5 responds to Mlsa-bearing B cells only in the presence of SAC.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship of Mlsx to Mlsc.

Among T cell clones with specificity for cow insulin and autologous class II MHC products, a significant number displayed interesting patterns of alloreactivity to non-MHC antigens. Four clones are described in this report. One is a typical Mlsa-reactive clone, while the other three proliferate to a variety of allogeneic spleen cells with reportedly different Mls phenotypes. These include PL/J stimulator cells, designated Mlsx, all strains reported to be Mlsc, and several strains previously typed as Mlsa. Little is known about Mlsx except that it does not appear to be cross-reactive with Mlsa. In this report, therefore, we attempt to investigate the reasons why these clones seem to be stimulated by a variety of different Mls phenotypes. Our conclusions are, first, that some of the strains previously typed as Mlsa may actually express a second Mls product, either c or x, in a manner analogous to the CBA/J strain (which expresses both Mlsa and Mlsc), and second, that Mlsc and Mlsx are cross-reactive. In preliminary experiments, we investigate the genetic relationship between Mlsc and Mlsx by analysis of backcrosses, and the extent of cross-reactive recognition of Mlsc and Mlsx by raising T cell clones which recognize one but not the other. Our preliminary conclusion is that Mlsc and Mlsx are cross-reactive, but represent distinct gene products.

Isolation of antigen-specific T cell clones from nonresponder mice.

The mechanisms responsible for major histocompatibility complex (MHC)-linked unresponsiveness are still poorly understood. Here we examine the cellular events that follow when B10. A mice are immunized with cow insulin, an antigen to which they make no apparent immunologic response. Despite the fact that there is no detectable antibody or T cell proliferative response to cow insulin, we have been able to clone out responding T cells after priming and restimulating in vitro with this "nonimmunogenic" antigen. These cells are L3T4+, and co-recognize specific antigen and class II MHC gene products. The data demonstrate that "nonresponder" mice to cow insulin have both the capacity to present antigen and T cells capable of recognizing that antigen. The diversity within this population was investigated by analyzing various parameters of cellular activation. These include fine specificity of both antigen and MHC recognition, as well as recognition of allogeneic MHC and M1s determinants. In addition, the antigen-presenting cell requirements were studied. The results demonstrate that this population comprise a surprisingly heterogeneous group in terms of its repertoire of receptors.