H-2-specific antibodies induced by injection of syngeneic leukemia cells

The costimulatory and differentiating activity of soluble class I MHC antigens for an autologous thymocyte population

Combined cultivation of macrophages with syngeneic thymocytes resulted in accumulation of soluble H-2Kk antigens in culture medium. Incubation of intact autologous thymocytes with these soluble class I MHC molecules was shown to induce functional maturation of thymocytes assayed in local graft-vs-host reaction. Similar thymocyte costimulating activity was detected for the papain-solubilized purified H-2Kk antigens. Soluble class I antigens were shown to costimulate IL2 production by thymocytes in response to submitogenic doses of exogenous IL2 and to increase PHA-induced thymocyte proliferation. Soluble class I molecules were shown to increase the level of expression of function-associated membrane antigens, H-2Kk, CD8 and CD4, and to trigger thymocyte differentiation. The expression of I-Ak antigens remained invariable. It was also shown that soluble autologous class I molecules may function as direct amplifiers of thymocyte proliferation in autologous, but not allogeneic, mixed leukocyte reactions. It is concluded that soluble MHC class I molecules are capable of triggering functional and phenotype differentiation of syngeneic thymocytes and acting as restricted coaccessory molecules when thymocyte activation is induced by a submitogenic dose of different stimuli.

Specificity of anti-H-2 class I antibodies induced by syngeneic immunization with Sendai virus-treated cells is regulated by the mouse MHC and viral antigens. No evidence for MHC-restricted virus-specific antibodies

In a previous study, we searched for Sendai virus (SV)-specific antibodies that were restricted in their binding by self-major histocompatability complex (MHC) antigens. In C57BL/6 (B6; H-2b) mice, most of the sera obtained after i.p. injections with syngeneic SV-coated (SV+) spleen cells contained auto- and alloreactive lymphocytotoxic antibodies directed against H-2 class I molecules, but no viral-specific, MHC-restricted antibodies. Here we report that syngeneic immunization with SV+ cells regularly induced H-2-specific antibodies in various mouse strains. From a total of 12 strains tested, only the B10.S (H-2s) strain appeared to be a low responder. The immune responses are of two types: (i) mice of some strains produce autoreactive antibodies and a broad variety of alloreactive antibodies; and (ii) mice of some strains produce only narrow or widely alloreactive antibodies. Because most of the strains differ only in the H-2 region, the patterns observed are regulated by the MHC. To locate the genes involved in the induction of H-2-specific antibodies more precisely, two B6 mutant strains, bm1 (Kb mutant) and bm13 (Db mutant), were immunized with syngeneic SV+ cells. The results suggest that the H-2Db region plays an important role in the induction and specificity of the lymphocytotoxic H-2 class I-specific antibodies present in sera of H-2b mice after syngeneic immunization with SV+ cells. The role of SV in the induction of H-2-specific antibodies was studied in B6 mice after injections of syngeneic cells coated with liposomes bearing the F and HN proteins of SV. The results suggest that SV surface glycoproteins as well as internal proteins are directly involved in regulating the specificity of anti-H-2 antibodies present in sera after syngeneic immunization with SV+ cells. This study does not support the concept that antigen-specific, MHC-restricted antibodies are a part of the B-cell repertoire.

Immunization with syngeneic Sendai virus-infected cells induce no MHC-restricted antibodies but antibodies specific for H-2 class I determinants

To find out whether immunoglobulins are able to recognize foreign antigens in the context of syngeneic MHC determinants, an effort was made to trigger the production of MHC-restricted antibodies by syngeneic Sendai virus (SV)-infected cells using the spleen-fragment culture technique. Antibodies were found that mimicked MHC-restricted antibodies by recognizing MHC+SV better than MHC alone. However, the binding was not specific for SV and also occurred on mitogen-stimulated (SV-) or influenza virus-infected cells. We describe the production of H-2 class I-specific lymphocytotoxic antibodies by primary B cells responding to syngeneic SV-infected cells. No viral-specific, H-2-restricted antibodies were found.