anti-MHC Antibodies Research Articles

Antigen presentation by liposomes: inhibition with antibodies.

The involvement of both antigen and class II major histocompatibility complex (MHC) molecules in T cell activation by liposome-bound antigens was investigated. We used a pigeon cytochrome c (PCC)-specific Ek-restricted T cell hybridoma that can be activated to produce interleukin 2 by liposomes carrying either PCC and Ek molecules, or a high concentration of PCC alone. We demonstrated that the MHC-restricted response of this hybridoma to liposomes is specifically blocked by both anti-MHC and anti-PCC monoclonal antibodies, whereas unrestricted activation is only inhibited by PCC-specific antibody.

Stimulation of alloreactive cytotoxic T cells by paternal major histocompatibility antigens during murine pregnancy.

In an effort to elucidate T cell reactivity toward paternal major histocompatibility (MHC) antigens during pregnancy, the ability of pregnant mice to develop alloreactive cytotoxic T lymphocytes (CTL) was studied in individual multiparous females mated with MHC congeneic strains of B10 background. Spleen cells obtained from B10.BR females mated to allogeneic males manifested strikingly higher CTL than those from animals mated to syngeneic males or from virgins; syngeneically mated animals were equivalent to virgin controls in CTL responses. The augmented CTL response in allogeneic pregnancy was detected not only by stimulation with the paternal MHC antigens but also by an unrelated MHC haplotype. However, this augmentation was found only during pregnancy in that 2-5 days after the delivery the CTL activity in allopregnant animals returned to a level comparable to that of virgin controls. No suppressor cells were detected at this stage. These observations suggest that maternal T cells recognize MHC disparity with the fetus in some way during pregnancy. Anti-MHC antibodies, immunoglobulin (Ig) M, and IgGs of all subclasses were not detected in these animals throughout multiple pregnancies.

Evidence for the role of class I and class II HLA antigens in the lytic function of a cloned line of human natural killer cells.

Monoclonal antibodies with specificity for HLA class I and class II antigens were generated which either inhibit or enhance the lytic activity of a cloned line of human NK cells. These antibodies were obtained from a fusion with spleen cells from mice immunized with NK clone 3.3. They affect the lytic function of that clone at the level of the killer cell; additional evidence suggests that the effect takes place during an early stage of lysis. Immunoprecipitation and cross-clearing experiments using MHC antibodies of known specificity demonstrate the reactivity of mAbs 131 and 164 with HLA class I antigens and mAbs 210 and 273 with HLA class II antigens. Binding studies indicate that these antibodies are probably recognizing nonpolymorphic MHC determinants. Although these antibodies bind to other NK effector cells tested, they have no effect on the lytic function of these bulk NK populations. Preliminary studies, however, indicate that they do affect the NK activity of a proportion of the clones within these bulk populations. To further assess the potential role of HLA gene products in the lytic function of NK3.3, several well-defined anti-MHC antibodies were tested for their effects on NK3.3 function. The anti-HLA class I and class II antibodies could each be grouped into functional categories based on their ability to enhance, inhibit, or not affect the lysis of NK-sensitive targets K562 and MOLT-4 by NK clone 3.3. These results demonstrate, for the first time, a potential involvement of MHC molecules with NK function.

Immunohistology of lymphoid and non-lymphoid cells in the thymus in relation to T lymphocyte differentiation.

The present paper reports the distribution of lymphoid and non-lymphoid cell types in the thymus of mice. To this purpose, we employed scanning electron microscopy and immunohistology. For immunohistology we used the immunoperoxidase method and incubated frozen sections of the thymus with 1) monoclonal antibodies detecting cell-surface-differentiation antigens on lymphoid cells, such as Thy-1, T-200, Lyt-1, Lyt-2, and MEL-14; 2) monoclonal antibodies detecting the major histocompatibility (MHC) antigens, H-2K, I-A, I-E, and H-2D; and 3) monoclonal antibodies directed against cell-surface antigens associated with cells of the mononuclear phagocyte system, such as Mac-1, Mac-2, and Mac-3. The results of this study indicate that subsets of T lymphocytes are not randomly distributed throughout the thymic parenchyma; rather they are localized in discrete domains. Two major and four minor subpopulations of thymocytes can be detected in frozen sections of the thymus: 1) the majority of cortical thymocytes are strongly Thy-1+ (positive), strongly T-200+, variable in Lyt-1 expression, and strongly Lyt-2+; 2) the majority of medullary thymocytes are weakly Thy-1+, strongly T-200+, strongly Lyt-1+, and Lyt-2- (negative); 3) a minority of medullary cells are weakly Thy-1+, T-200+, strongly Lyt-1+, and strongly Lyt-2+; 4) a small subpopulation of subcapsular lymphoblasts is Thy-1+, T-200+, and negative for the expression of Lyt-1 and Lyt-2 antigens; 5) a small subpopulation of subcapsular lymphoblasts is only Thy-1+ but T-200- and Lyt-; and 6) a small subpopulation of subcapsular lymphoblasts is negative for all antisera tested. Surprisingly, a few individual cells in the thymic cortex, but not in the medulla, react with antibodies directed to MEL-14, a receptor involved in the homing of lymphocytes in peripheral lymphoid organs. MHC antigens (I-A, I-E, H-2K) are mainly expressed on stromal cells in the thymus, as well as on medullary thymocytes. H-2D is also expressed at a low density on cortical thymocytes. In general, anti-MHC antibodies reveal epithelial-reticular cells in the thymic cortex, in a fine dendritic staining pattern. In the medulla, the labeling pattern is more confluent and most probably associated with bone-marrow-derived interdigitating reticular cells and medullary thymocytes. We discuss the distribution of the various lymphoid and non-lymphoid subpopulations within the thymic parenchyma in relation to recently published data on the differentiation of T lymphocytes.

Human cytotoxic T lymphocytes (CTL) against Epstein-Barr virus (EBV) infected cells: EBV specificity and involvement of major histocompatibility complex determinants in the lysis exerted by anti-EBV CTL toward HLA-compatible and allogeneic target cells

Human peripheral blood lymphocytes (PBL), from anti-Epstein-Barr virus (EBV)-seropositive donors, were stimulated by EBV and were shown to be cytotoxic toward autologous, HLA-compatible, and fully allogeneic EBV-transformed target cells. The lysis was not due to natural killer (NK) cells since the target cells used were resistant to lysis by fresh PBL and by virus-stimulated PBL-depleted of AET-SRBC-rosetting T cells (the latter being still fully cytotoxic on K562 NK-susceptible target cells). Conversely only E-rosette-purified (T) lymphocytes killed EBV-transformed HLA-compatible and allogeneic target cells. Moreover, anti-MHC antibodies inhibited the cytotoxicity exerted by EBV-induced cytotoxic T lymphocytes (CTL) on both autologous and allogeneic target cells. Finally the lysis was EBV specific since PHA blasts were not killed and since only EBV-transformed cells could compete for lysis with the EBV-positive target cells. Efficient competition was achieved by EBV-transformed cells autologous or allogeneic to the targets, even when effector and target cells were fully allogeneic. All together, the data suggest that human anti-EBV CTL may recognize nonpolymorphic HLA determinants on the target cells in association with the virus-induced antigens.

Idiotypes of anti-major histocompatibility complex antibodies.

Our studies to date indicate that treatment with anti-idiotype to monoclonal anti-MHC antibodies can markedly influence the repertoire of anti-MHC antibodies expressed. The antibodies discussed here appear to represent two classes, one of which is public, probably representing expression of a germ line gene, and the second of which probably represents either a somatic variant of a germ line gene or one of a very large number of germ line genes devoted to the same specificity. In either case, this class of idiotype arises only rarely following antigen, but is readily induced by anti-idiotype treatment. There may indeed exist a third class of anti-MHC monoclonal antibodies representing distant somatic diversification from a germ line gene. Our only indication of this so far is that certain idiotypes are only induced after multiple boosts with anti-idiotypes rather than a single treatment. This finding, however, may reflect again the enormous number of different ways in which anti-MHC antibodies to the same nominal specificity can be produced. Finally, our results in adoptive transfer systems indicate that manipulation of idiotype expression by anti-idiotype treatment probably involves a complex pathway of cellular interactions. If, as we expect, these intercellular interactions involve idiotype and/or anti-idiotypic receptors, they should provide a model for mechanistic studies of the in vivo immune network.

Anti-idiotypes against anti-H-2 antibodies VI. Detection of shared idiotypes among monoclonal anti-H-2 antibodies.

Anti-idiotypes produced against monoclonal anti-H-2 antibodies have been used to examine idiotope sharing among a panel of anti-major histocompatibility complex (MHC) antibodies detecting the same and different specificities. Both xenogeneic anti-100-30 and anti-3-83, which did not react with predominant idiotypes in conventional alloantisera, detected idiotopes on 3-83 and 100-30 as well as on 2 other monoclonal anti-H-2Kk antibodies. All 4 monoclonal antibodies recognized the same epitope cluster on the Kk molecule and detected the same serological specificity. H-2.5. In contrast, syngeneic and allogeneic anti-idiotype produced against the same monoclonal antibodies did not detect these cross-reactive determinants. In several instances, xenogeneic anti-idiotype reacted with anti-MHC antibodies which recognized distinct H-2 determinants, suggesting that anti-MHC antibodies detecting the same or different specificities may share idiotypic determinants. These reagents may be useful probes of the anti-MHC immune repertoire.

Protection against graft vs. host-associated immunosuppression in F1 mice. I. Activation of F1 regulatory cells by host-specific anti-major histocompatibility complex antibodies.

Injection of parental spleen cells into unirradiated F1 hybrid mice results in suppression of the potential to generate cytotoxic T lymphocyte (CTL) responses in vitro. In an attempt to protect the F1 mice from immunosuppression, the recipients were injected with antibodies specific for major histocompatibility complex (MHC)-encoded antigens of the F1 mice 24 h before inoculation of the parental spleen cells. 8-14 d later, the generation of CTL responses in vitro against H-2 alloantigens was tested. Alloantiserum directed against either parental haplotype of the F1 strain markedly diminished the suppression of CTL activity. Furthermore, monoclonal antibodies recognizing H-2 or Ia antigens protected the F2 mice from parental spleen cell-induced suppression. Although this study has been limited to reagents that recognize host H-2 determinants, these findings do not necessarily imply that protection against graft vs. host (GvH) can be achieved only with anti-MHC antibodies. However, protection was observed only by antibodies reactive with F1 antigens, and small amounts of the alloantibodies were sufficient to diminish CTL suppression. Adoptive transfer of spleen cells from syngeneic F1 mice treated with anti-h-2a alloantiserum 24 h previously provided protection equal to that of injection of the recipients with alloantibodies. The cells necessary for this effect were shown to be T cells and to be radiosensitive to 2000 rad. This cell population is induced by antisera against F1 cell surface antigens and effectively counteracts GvH-associated immuno-suppression.

Anti-MHC antibody idiotypes as important elements in immunoregulation

Anti-MHC antibody idiotypes as important elements in immunoregulation

The blocking effect of antibodies against the products of the H-2 gene complex on lymphocyte complement (C3d) receptors. complement dependence and specificity.

Antisera against the products of the major histocompatibility system (MHS), produced by immunization between congenic mouse strains differing only at that segment of the 17th chromosome rosettes which bears the H-2gene complex, exert a reproducible blocking effect on formation of with EACm (C3d rosettes). In many instances this effect is probably due to specific antibodies reactive with the lymphocytes, as indicated by immunochemical and adsorption experiments. Purified antibodies from the C3H anti-C3H.B10 immune ascites failed to exert this blocking effect. The blocking capacity can be restored, however, by addition of fresh normal mouse, rabbit or fetal calf serum, but not by heat inactivated serum. These experiments show that the presently defined H-2K, H-2D and H-2L antigens as well as some Ia antigens are themselves not the C3d receptors. The blocking effects observed in the presence of complement are possibly due to the proximity of H-2 or Ia molecules and C3d receptors, or to a rearrangement of membrane components after reaction with anti-MHC anti-MHC antibodies and complement.

Expression of MHC Antigens by Mouse Thymic Dendritic Cells

Thymic epithelial cells express MHC antigens in several different patterns. I-A is present throughout the thymic cortex on dendritic cells. The remainder of the I region and H-2K/D are expressed on dendritic cells apparently only variably in the cortex (at least in some haplotypes). All MHC antigens tested are present in the medulla on epithelial cells; expression on medullary lymphocytes cannot be evaluated. Monoclonal anti-MHC antibodies confirm these results. The significance of these findings to T cell maturation is discussed.