Adoptive transfer of nontransgenic mesenteric lymph node cells induces colitis in athymic HLA-B27 transgenic nude rats.

HLA-B27 transgenic (TG) rats develop spontaneous colitis when colonized with intestinal bacteria, whereas athymic nude (rnu/rnu) HLA-B27 TG rats remain disease free. The present study was designed to determine whether or not HLA-B27 expression on T cells is required for development of colitis after transfer of mesenteric lymph node (MLN) cells into rnu/rnu HLA-B27 recipients. Athymic nontransgenic (non-TG) and HLA-B27 TG recipients received MLN cells from either TG or non-TG rnu/+ heterozygous donor rats that contain T cells. HLA-B27 TG rnu/rnu recipients receiving either non-TG or TG MLN cells developed severe colitis and had higher caecal MPO and IL-1beta levels, and their MLN cells produced more IFN-gamma and less IL-10 after in vitro stimulation with caecal bacterial lysate compared to rnu/rnu non-TG recipients that remained disease free after receiving either TG or non-TG cells. Interestingly, proliferating donor TG T cells were detectable one week after adoptive transfer into rnu/rnu TG recipients but not after transfer into non-TG recipients. T cells from either non-TG or TG donors induce colitis in rnu/rnu TG but not in non-TG rats, suggesting that activation of effector T cells by other cell types that express HLA-B27 is pivotal for the pathogenesis of colitis in this model.

Reduced ratio of protective versus proinflammatory cytokine responses to commensal bacteria in HLA-B27 transgenic rats.

Germ-free HLA-B27 transgenic (TG) rats do not develop colitis, but colonization with specific pathogen-free (SPF) bacteria induces colitis accompanied by immune activation. To study host-dependent immune responses to commensal caecal bacteria we investigated cytokine profiles in mesenteric lymph node (MLN) cells from HLA-B27 TG versus nontransgenic (non-TG) littermates after in vitro stimulation with caecal bacterial lysates (CBL). Supernatants from CBL-stimulated unseparated T- or B- cell-depleted MLN cells from HLA-B27 TG and non-TG littermates were analysed for IFN-gamma, IL-12, TNF, IL-10 and TGF-beta production. Our results show that unfractionated TG MLN cells stimulated with CBL produced more IFN-gamma, IL-12 and TNF than did non-TG MLN cells. In contrast, CBL-stimulated non-TG MLN cells produced more IL-10 and TGF-beta. T cell depletion abolished IFN-gamma and decreased IL-12 production, but did not affect IL-10 and TGF-beta production. Conversely, neither IL-10 nor TGF-beta was produced in cultures of B cell-depleted MLN. In addition, CD4(+) T cells enriched from MLN of HLA-B27 TG but not from non-TG rats produced IFN-gamma when cocultured with CBL-pulsed antigen presenting cells from non-TG rats. Interestingly, IL-10 and TGF-beta, but not IFN-gamma, IL-12 and TNF were produced by MLN cells from germ-free TG rats. These results indicate that the colitis that develops in SPF HLA-B27 TG rats is accompanied by activation of IFN-gamma-producing CD4(+) T cells that respond to commensal bacteria. However, B cell cytokine production in response to components of commensal intestinal microorganisms occurs in the absence of intestinal inflammation.

Disrupted B-lymphocyte development and survival in interleukin-2-deficient mice.

Interleukin-2-deficient (IL-2-/-) mice develop a spontaneous, progressive, CD4+ T-cell-mediated colitis with an age-related decrease in the number of B lymphocytes. The aim of this study was to determine the mechanisms of B-cell loss in IL-2-/- mice. Serum immunoglobulin G1 (IgG1) levels in 8-week-old IL-2-/- mice were above normal but then decreased dramatically with advancing age. Between 8 and 11 weeks of age, the number of B-cell progenitors (B220+ IgM-) in the bone marrow of IL-2-/- mice was less than half of those in IL-2+/+ littermates. By 22 weeks of age, very few progenitor cells remained in the bone marrow of most mice, and spleens were almost devoid of B cells. Likewise, B1 cells were not present in the peritoneal cavity of aged IL-2-/- mice. Flow cytometry analysis of B-cell differentiation in the bone marrow suggested a progressive loss of B cells from the most mature to the least mature stages, which was not dependent on IL-2 receptor-alpha (IL-2Ralpha) expression. B cells transferred from normal animals had similar survival rates in IL-2-/- and wild-type mice. We conclude that conventional B cells in older IL-2-/- mice are lost by attrition owing to a derangement in B-cell development. Because B1 cells are less dependent on the bone marrow, a separate mechanism for their loss is suggested.

Continuous stimulation by normal luminal bacteria is essential for the development and perpetuation of colitis in Tg(epsilon26) mice.

BACKGROUND & AIMS: Normal resident bacteria are required for development of colitis in several rodent models. We determined whether bacterial stimulation is necessary for both induction and perpetuation of mucosal inflammation and T-cell activation in Tg(epsilon26) mice, in which transplantation of wild-type bone marrow (BM-->Tg(epsilon26)) causes colitis under specific pathogen-free (SPF) conditions. METHODS: BM from (C57BL/6 X CBA/J) F1 mice was transplanted into germfree (GF) or SPF Tg(epsilon26) mice. Mesenteric lymph node (MLN) cells from these mice were then transferred into SPF or GF recipients. Colitis and activation of MLN cells were measured by histologic scores, membrane marker analysis, and intracellular cytokine staining. Cytokine secretion by MLN cells stimulated by anti-CD3 or by luminal or epithelial antigens was measured by ELISA. RESULTS: Colitis did not develop when BM was transferred into GF recipient mice (BM-->GF Tg(epsilon26)). T lymphocytes that secreted interferon gamma upon activation were present in the MLN of BM-->GF Tg(epsilon26) mice, albeit in lower frequency than in control BM-->SPF Tg(epsilon26) mice. Furthermore, transfer of MLN cells from BM-->SPF Tg(epsilon26) mice into SPF Tg(epsilon26) recipients induced active colitis, but not if the same cells were transferred into GF Tg(epsilon26) recipients. Although CD4 T cells were detected in the colonic mucosa of GF recipients, no inflammation was observed for at least 31 weeks. In a reciprocal experiment, MLN cells from BM-->GF Tg(epsilon26) mice without colitis transferred disease to SPF Tg(epsilon26) recipients within 2-4 weeks. CONCLUSIONS: Activated T cells are present in the mucosa of BM-->GF Tg(epsilon26) mice but are incapable of inducing disease unless colonic bacteria are present. Moreover, pathogenic T cells require the continuous presence of colonic bacteria to sustain colitis.

Natural killer cell-dependent immunoglobulin G2a anti-bovine serum albumin (BSA) response elicited by high molecular weight dextran-BSA conjugates associated with dextran-mediated macrophage-natural killer cell interaction.

The roles of the interferon-gamma (IFN-gamma) and interleukin-12 (IL-12) produced during natural killer (NK) cell interaction with macrophages (M phi) were investigated as the basis for the induction of immunoglobulin G2a (IgG2a) anti-bovine serum albumin (BSA) responses by high molecular weight dextran conjugated to BSA (HMW-DEX-BSA). BALB/c mice immunized with HMW-DEX-BSA produced significantly higher levels of both IgG1 and IgG2a anti-BSA than did mice immunized with BSA alone. Both IgG1 and IgG2a anti-BSA levels were higher in mice immunized with BSA conjugated to dextran of molecular weight (MW) 5 000 000-40 000 000 compared with dextran of MW 10,000-60,000. The enhancement of anti-BSA IgG2a levels but not of anti-BSA IgG1 levels was inhibited when free BSA was added to the HMW-DEX-BSA conjugate. NK cell depletion during HMW-DEX-BSA immunization of mice resulted in significantly lower anti-BSA IgG2a levels without affecting anti-BSA IgG1 levels. Naive splenocytes or M phi + NK cell co-cultures incubated with HMW-DEX or HMW-DEX-BSA produced higher IFN-gamma levels than splenocytes or co-cultures incubated with BSA alone. HMW-DEX stimulated both IFN-gamma and IL-12 production by M phi + NK cell co-cultures in a dose-dependent manner. DEX-induced IFN-gamma production by NK cells was dependent upon the presence of IL-12, and IL-12 production by M phi was dependent upon the presence of IFN-gamma in these co-cultures. Both M phi and NK cells bound DEX to their surfaces. These data demonstrate that BSA linked to HMW-DEX enhanced both T-helper-1- and T-helper-2-associated antibody responses to BSA. The results also indicate an IL-12-dependent positive feedback interaction between NK cells and M phi that supports a NK cell/IFN-gamma-dependent mechanism for enhancement of anti-BSA IgG2a antibody responses in mice immunized with HMW-DEX-BSA protein conjugates.

Helicobacter hepaticus does not induce or potentiate colitis in interleukin-10-deficient mice.

Helicobacter hepaticus has been reported to induce colitis, hepatitis, and hepatocellular carcinoma in several different murine models. The aim of this study was to determine if H. hepaticus will cause colitis in monoassociated mice lacking the interleukin-10 gene (IL-10(-/-) mice) and potentiate colitis in specific-pathogen-free (SPF) IL-10(-/-) mice. Germfree IL-10(-/-) mice on either a mixed (C57BL/6 x 129/Ola) or inbred (129/SvEv) genetic background were monoassociated with H. hepaticus ATCC 51448 by oral feeding and rectal enemas. In a second experiment, germfree IL-10(-/-) mice were colonized with stool from SPF mice that harbored or did not harbor endogenous H. hepaticus. After 7 to 9 weeks of colonization, weight loss and mortality were assessed, the colon was isolated for histology and IL-12 secretion, and mesenteric lymph node cells were assessed for T-cell activation markers. It was found that IL-10(-/-) mice monoassociated with H. hepaticus for up to 16 weeks showed almost no histologic colitis or increased IL-12 production. SPF IL-10-knockout mice had no significant difference in weight loss, mortality rate, histologic scores, colonic IL-12 secretion, or T-cell activation with or without H. hepaticus. We conclude that H. hepaticus does not induce or potentiate disease in our IL-10(-/-) mice and therefore is not required to induce colitis in genetically susceptible hosts.

Interleukin 2, but not other common gamma chain-binding cytokines, can reverse the defect in generation of CD4 effector T cells from naive T cells of aged mice.

Development of effectors from naive CD4 cells occurs in two stages. The early stage involves activation and limited proliferation in response to T cell receptor (TCR) stimulation by antigen and costimulatory antigen presenting cells, whereas the later stage involves proliferation and differentiation in response to growth factors. Using a TCR-transgenic (Tg(+)) model, we have examined the effect of aging on effector generation and studied the ability of gamma(c) signaling cytokines to reverse this effect. Our results indicate that responding naive CD4 cells from aged mice, compared with cells from young mice, make less interleukin (IL)-2, expand poorly between days 3 to 5, and give rise to fewer effectors with a less activated phenotype and reduced ability to produce cytokines. When exogenous IL-2 or other gamma(c) signaling cytokines are added during effector generation, the Tg(+) cells from both young and aged mice proliferate vigorously. However, IL-4, IL-7, and IL-15 all fail to restore efficient effector production. Only effectors from aged mice generated in the presence of IL-2 are able to produce IL-2 in amounts equivalent to those produced by effectors generated from young mice, suggesting that the effect of aging on IL-2 production is reversible only in the presence of exogenous IL-2.

IL-2-deficient mice raised under germfree conditions develop delayed mild focal intestinal inflammation.

Interleukin-2 (IL-2) amplifies immune stimuli and influences B cell differentiation. IL-2-deficient mice spontaneously develop intestinal inflammation if raised under specific pathogen-free (SPF) conditions. We quantitatively determined the aggressiveness and kinetics of gastrointestinal and hepatic inflammation in the presence or absence of viable bacteria in IL-2-deficient mice. Breeding colonies were maintained under SPF and germfree (GF) conditions. Intestinal tissues, serum, and mesenteric lymph nodes were obtained from mice at different ages for blind histological scoring, immunoglobulin measurements, mucosal T cell infiltration, and cytokine secretion. GF IL-2 -/- mice developed mild, focal, and nonlethal intestinal inflammation with delayed onset, whereas the more aggressive inflammation in SPF IL-2 -/- mice led to their death between 28 and 32 wk. Periportal hepatic inflammation was equal in the presence or absence of bacterial colonization. Intestinal immunoglobulin secretion decreased significantly by 13 wk of age in IL-2 -/- mice in both GF and SPF environments. In contrast to other genetically engineered rodents, IL-2 -/- mice develop mild focal gastrointestinal and active portal tract inflammation in the absence of viable bacteria.

Blockade of both L-selectin and alpha4 integrins abrogates naive CD4 cell trafficking and responses in gut-associated lymphoid organs.

The recirculation of naive lymphocytes from blood to lymph that is initiated in high endothelial venules (HEV) of secondary lymphoid organs such as lymph nodes and Peyer's patches (PP) is regulated by multiple interactions of adhesion receptor/counter-receptor pairs involving both selectins and integrins. We showed previously that blocking of only L-selectin is sufficient to ablate trafficking of naive CD4 cells and the development of their responses in peripheral lymph nodes but not in PP where alpha4beta7 integrins are thought to primarily regulate entry. However, although antibody to alpha4 integrins partially inhibited homing of naive CD4 cells to PP and not to lymph nodes, there was no effect on the development primary responses in these tissues or spleens. Since previous studies indicate that both alpha4beta7 integrins and L-selectin regulate adhesion of naive cells to PP HEV, we examined the effect a blockade of both adhesion pathways on the recirculation of naive CD4 cells. There was no detectable homing of naive CD4 cells to PP or lymph nodes when interactions with both receptors were inhibited, resulting in a profound depletion of naive CD4 cells and loss of antigen responses in these sites. In contrast, increased numbers of naive CD4 cells and responses of higher magnitude were found in the spleen. The results demonstrate recirculation of naive CD4 cells through tissues where entry is controlled through HEV is essential for the local generation of primary responses.

L-selectin is not essential for naive CD4 cell trafficking or development of primary responses in Peyer's patches.

We showed previously that L-selectin-dependent recirculation of naive CD4 cells is essential for development of primary responses in peripheral lymph nodes. Recent studies suggest that L-selectin is also required for lymphocyte entry into gut mucosal lymphoid tissues that include Peyer's patches and mesenteric lymph nodes. Here we show that anti-L-selectin antibody, MEL-14, inhibited homing of a rigorously purified, homogenous population of naive CD4 cells into both of these tissues as well as peripheral lymph nodes, directly demonstrating a role for this receptor in regulating entry into gut-associated sites. However, in intact animals, treatment with MEL-14 resulted in the loss of naive CD4 cells (CD45RBhi, CD44lo from peripheral lymph nodes but not Peyer's patches, whereas mesenteric lymph nodes were intermediate in this regard. In mice primed by parenteral immunization with keyhole limpet hemocyanin (KLH), primary CD4 responses were readily detected in both. Peyer's patches and mesenteric lymph nodes, and were not affected by exposure to MEL-14. Indeed, similar frequencies of KLH-specific CD4 cells were recovered from both of these tissues irrespective of MEL-14 treatment. The results indicate that interactions with L-selectin can be circumvented to allow entry of naive CD4 cells into Peyer's patches but not peripheral lymph nodes.

Sensitized liposomes as an antigen delivery system for the stimulation of mucosal immunity.

This study was designed to exploit the ability of Peyer's patch M cells to recognize antigen-antibody complexes in the targeted delivery of a model antigen for the induction of mucosal immunity. Sensitized liposomes consisted of an entrapped model antigen, ovalbumin (OVA), and coated with unrelated antigen-antibody complexes. Sensitized liposomes were administered intrajejunally to mice either with or without monophosphoryl lipid A (MLA). Humoral immune responses were monitored in saliva, feces, serum, and bile. Mice which received sensitized liposomes showed up to 4-fold amounts of specific IgA in saliva, feces, and bile compared to controls. Transient increases in anti-OVA IgA and IgG were observed in serum. Formulations including MLA generated positive anti-OVA IgG responses in both serum and bile. In separate experiments, cell proliferation studies were performed with Peyer's patch lymphocytes harvested from mice immunized with OVA in either standard or sensitized liposomes. Lymphocytes from test mice receiving only sensitized liposomes proliferated in the presence of OVA, but not an unrelated antigen. Taken together, these results support the potential application of antigen-antibody complexes in the stimulation of mucosal immune responses and that MLA may play an important role in overcoming OVA tolerogenicity.

Immune System Activation in C3H/HeJBir Mice Exhibiting Spontaneous Perianal Ulceration.

: We report our initial characterization of the immune system in C3H/HeJBir mice that spontaneously develop perianal ulceration. Analysis of lymphokine production by mucosal and systemic lymphoid cells obtained from these mice revealed higher levels of interleukin (IL)4 in supernatants of in vitro stimulated Peyer's patch and mesenteric lymph node cells from C3H/HeJBir mice with severe perianal lesions than from C3H/HeJBir mice with mild perianal lesions or from normal C3H/HeJ mice. Supernatants that contain the highest amounts of IL-4 contain the lowest amounts of interferon (IFN)-γ. Peyer's patches and mesenteric lymph nodes of C3H/HeJBir mice with severe perianal lesions contain approximately four-fold fewer cells; however, inguinal lymph nodes contain up to 25-fold more cells compared with C3H/HeJ mice. These inguinal lymph node cells secrete IL-6, and T cells that produce IL-2 or IFN-γ can be demonstrated. Serum IgE, IgGl, and IgG2a are all increased in C3H/HeJBir mice with severe perianal ulceration. These results show that C3H/HeJBir mice with grossly evident inflammation have activated lymphocytes in both mucosal and systemic lymphoid organs. Understanding mechanisms of lymphocyte activation and regulation in these mice may provide insights into the pathogenesis of perianal ulceration that is often associated with Crohn's disease.

Distinct lymphokine production by CD4+ T cells isolated from mucosal and systemic lymphoid organs.

We have investigated the potential of CD4+ T cells isolated from Peyer's patches and mesenteric lymph nodes (mucosa-associated lymphoid tissues) and from spleens and peripheral lymph nodes (systemic lymphoid tissues) to secrete a variety of lymphokines. The results show several pronounced differences in the kinetics of lymphokine production and in the levels of lymphokines detected after primary and secondary in vitro stimulation with immobilized anti-CD3. The most striking difference was seen in the production of interleukin-4 (IL-4). Supernatants of splenic CD4-bearing cells collected at early time-points after primary stimulation contained high levels of IL-4. Supernatants of Peyer's patch and mesenteric lymph node CD4+ T cells contained considerably lower levels of IL-4 at all time-points analysed, while supernatants of peripheral lymph node CD4+ T cells contained high levels of IL-4, but only at late time-points. Neither cell concentration nor availability of accessory cells appeared to account for the differences observed in IL-4 production by the CD4+ T cells studied. Splenic CD4+ T cells most rapidly and effectively used the IL-4 they produced, as determined by analysing IL-4 production after restimulation. Therefore, we conclude that the spleen is a more potent source of IL-4 than are the mucosa-associated lymphoid tissues studied here. Amounts of IL-2, IL-3, IL-5, and IL-6 were similar in supernatants of all of the CD4+ T cells studied. Peyer's patch CD4+ T-cell supernatants contained the lowest levels of interferon-gamma and peripheral lymph node supernatants displayed the highest accumulation of this lymphokine.

Regulation of isotype production by IL-4 and IL-5. Effects of lymphokines on Ig production depend on the state of activation of the responding B cells.

The effects of IL-4 and IL-5 on the production of Ig of different isotypes was investigated. We compared B cells from spleen and from Peyer's patches either stimulated with LPS or without added polyclonal stimulation. We also compared high density (small) and low density (large) B cells. The effect of lymphokines depended on the size and source of the B cells as well as on whether LPS was added. As expected, small B cells from either lymphoid compartment responded to LPS alone and IL-4 suppressed IgM and IgG3 production and enhanced IgG1. In contrast, when large B cells were examined, the suppressive effects of IL-4 were much less apparent but the enhancement of IgG1 was still marked. IL-5 alone had only minimal effects in LPS-stimulated cultures but the combination of IL-4 plus IL-5 appeared to overcome much of the IL-4-mediated suppression of IgM, and IgA production was enhanced. In the absence of LPS, a quite different profile is seen. First, small B cells make little if any response. Second, there is dramatic synergy between IL-4 and IL-5 in the response of large B cells, which is independent of isotype. Third, IL-4 does not suppress any isotype in the absence of LPS. Fourth, IL-4 plus IL-5 stimulate large Peyer's patch B cells to produce 10 times more IgA but three times less IgM than large spleen B cells. Fifth, Th2 cells directly stimulate both large and small B cells.

Stimulation of gut-associated lymphoid cells by IL-4 and B-cell growth factor II.

We have analysed the ability of B cells isolated from the Peyer's patches of normal mice to respond to two different B-cell stimulatory factors. Peyer's patch B cells respond in vitro to co-stimulation by either interleukin-4 (IL-4) plus anti-IgM or B-cell growth factor II (BCGF-II) plus dextran sulphate (DXS). We have consistently observed that splenic B cells proliferate more than Peyer's patch B cells when co-stimulated by BCGF-II plus DXS. This is not due to a diminished proliferation capacity of the Peyer's patch B-cell preparations, because the Peyer's patch B cells often proliferate more than splenic B cells when co-stimulated with IL-4 plus anti-IgM. These differences are not a result of altered response kinetics or differences in relative amounts of surface IgM on the two types of B cells. We have also analysed B cells from the LPS hypo-responsive strain C3H/HeJ, and its LPS responsive partner strain C3H/OuJ, from the X-linked immunodeficient strain (xid), CBA/N, and from germ-free (GF) mice. B cells from spleens and Peyer's patches of GF mice are responsive to co-stimulation by IL-4 plus anti-IgM and to co-stimulation by BCGF-II plus DXS. Peyer's patch B cells from C3H/HeJ mice proliferate as well as Peyer's patch B cells from C3H/OuJ cells to both co-stimulation protocols. Among the types of B cells studied here, only cells from spleens and Peyer's patches of mice that bear the xid defect fail to respond to the signals delivered by lymphokine co-stimulation. Our results suggest that while Peyer's patch B cells are stimulated by these two lymphokines, Peyer's patches contain cells that react differently from spleen cells to either the lymphokines IL-4 and BCGF-II, or the co-stimulators anti-IgM or dextran sulphate.

A method for the accurate determination of the specificity of monoclonal antibodies reactive with porcine immunoglobulins.

Monoclonal antibodies against porcine IgG were produced by fusion and characterized. The supernatants of microtiter wells containing fusion hybrids were first screened with an ELISA using semi-purified porcine IgG as antigen. Hybrids reactive in ELISA were cloned by limiting dilution. Further characterization of the specificity of the monoclonal antibodies was done by a combination of two methods: SDS-PAGE electroimmunoblotting and convection blotting of immunoelectrophoretic patterns (IEP-immunoblotting). Using these techniques, we identified monoclonal antibodies specific for porcine Ig gamma chains.

Analysis of the B10.D2-H-2dml mutant with monoclonal antibodies.

We compared H-2D products of B10.D2 and the mutant B10.D2-H-2dml spleen cells using two monoclonal antibodies designated D3.179 and S11.7. D3.179 reacts with public specificities and appears to define more than one product as shown by cytotoxicity and binding studies. Strong reactivity was obtained in both binding and cytotoxicity to B10.D2 and marginal cytotoxicity and low binding were observed with B10.D2-H-2dml cells. The second monoclonal antibody S11.7, in contrast, reacts only with H-2Dd bearing strains and gave strong binding to B10.D2-H-2dml and weaker binding to B10.D2. Taken together, the observations indicate that the mutant not only expresses H-2D encoded antigens but bears quantitatively greater amounts of some specificities than the parent. A product of approximately 46,000 daltons was immunoprecipitated from B10.D2 cells by D3.179. Very small amounts of this product were seen in B10.D2-H-2dml immunoprecipitates.

Paired H-2-specific monoclonal antibodies react differently to red cells and lymphocytes.

Two hybrid clones from a fusion of C57BL/6 anti-DBA/2 spleen cells and the myeloma line Sp2/0 secrete antibodies reactive with a product of the murine major histocompatibility complex (MHC). The two antibodies are provisionally designated S13.11 and S13.29. Both react in rabbit-complement-mediated cytotoxicity with spleen cells of H-2d, H-2f, H-2r, and H-2p strains. In addition, both antibodies hemagglutinate red blood cells from these strains. S13.11 is also cytotoxic for H-2a, H-2k, H-2u, and H-2v spleen cells but does not hemagglutinate red blood cells from mice bearing these haplotypes. With the exception of H-2v, this strain pattern mimics the public specificity H-28. Quantitative absorption of S13.11 shows that H-2d cells are twice as efficient as H-2k cells in their ability to remove the S13.11 antibody. S13.29 reacts weakly in cytotoxicity with H-2k spleen cells and does not react with cells from H-2u or H-2v. Blocking studies indicate that S13.11 and S13.29 react with the same or a closely related molecule on the cell surface.

A new alloantigenic system associated with the Mls locus in the mouse.

An antiserum prepared by injecting C3H/HeJ mice with CBA/J tissue has been shown to react with cell surface components that are not part of any previously described system of serologically detectable alloantigens. The antiserum, which is designated AST-101, acts selectively in cytotoxic tests carried out with lymphoid cells, killing B cells, but not T cells. Phagocytic cells found in peritoneal exudates are also killed by AST-101 and complement in vitro; the sensitivity of other cell types has not been determined. Strain distribution does not indicate any association of the AST-101 system with H-2, Ly, or Thy systems; genetic analysis reveals close linkage with the mouse minor MLC-stimulating (Mls) locus. Serologic analysis also points to a close association between antigens reactive with AST-101 and the products of the Mls genes.