Cell-mediated cytotoxicity to non-MHC alloantigens on mouse epidermal cells. VI. Influence of the MHC on the tissue specificity of cytotoxic T-lymphocyte responses

Tissue-specific and tissue-restricted histocompatibility antigens

Strictly defined, tissue-specific antigens are antigens characteristic of one particular tissue or cell. They are usually associated with autoimmunity and are remarkably homologous between species. In contrast, histocompatibility (H) antigens reflect polymorphism within species - they are alloantigens - and class-I major H complex (MHC) antigens - at least mouse H-2D and H-2 K and human HLA-A and -B, the commonest targets of acute allograft rejection - are widely distributed in the body; class-II MHC antigens - mouse Ia and human DR - have a much more limited distribution, being expressed primarily on B lymphocytes and on macrophages and other cells involved in antigen presentation and immune activation. This review is devoted to H antigens other than class-IIMHC antigens with limited if not highly specific, tissue distribution. Some of these antigens are classic tissue-specific antigens, others are alloantigens with limited tissue expression. Much of the evidence that they evoke immune responses that damage or destroy transplanted tissue is incomplete or circumstantial, but some is convincing and includes the immunogenetic characterization of new antigen systems that may have to be reckoned with clinically, especially when dealing with HLA-matched transplants.

Strain differences in the expression of the Epa-1-restricting element

Epa-1-specific cytotoxic T lymphocytes (CTL) lyse epidermal cells (EC) of different Epa-1+ H-2k strains, such a AKR, CBA, C58, and RF, at different levels. We used an H-2Kk-specific monoclonal antibody (mAb) to test the hypothesis that this phenomenon is due to differences in the H-2-restricting element. Initially, we established the specificity of this mAb for the Epa-1-restricting element by demonstrating its capacity to inhibit the lysis of CBA EC by Epa-1-specific CTL. We then used it as the probe in a cellular radioimmunoassay to quantify the expression of the restricting element by EC of different H-2k strains. We found that C58 and RF EC bound significantly less of the mAb than did CBA EC. Although AKR also bound less of the mAb than did CBA EC, the difference was not statistically significant. To examine the generality of this phenomenon, we quantified the expression of Kk antigens on spleen cells (SC) of the same four strains. We found that RF SC, but not AKR or C58 SC, bound significantly less of the Kk mAb than did CBA SC. Thus, the differential CTL lysis of Epa-1+ EC of different strains probably reflects differences in expression of the H-2-restricting element rather than of the nominal antigen.

Lysis of mouse macrophages, fibroblasts, and epidermal cells by epidermal alloantigen-specific cytotoxic T lymphocytes: effect of culture and inflammatory agents on Epa-1 expression

The expression of Epa-1, a tissue-restricted non-major histocompatibility complex (MHC) alloantigen, on CBA epidermal cells (EC), fibroblasts (FB), and macrophages (M phi) was investigated using bulk-cultured and clonally-derived anti-Epa-1 cytotoxic T lymphocytes (CTL). Epa-1 was readily detected on freshly trypsinized and 24-hr-cultured EC, and on skin FB cultured for 1-3 weeks. In contrast, fresh peritoneal (PE) M phi were specifically resistant to Epa-1 CTL but became susceptible after 12-24 hr in culture. Epa-1 expression by PE M phi also could be induced in vivo by M phi-activating agents such as concanavalin A or Bacillus Calmette-Guérin (BCG), but not by the sterile inflammatory agents peptone broth or thioglycolate, suggesting a correlation between Epa-1 phenotype and M phi activation. From this and from parallel studies of spleen cell M phi it is concluded that Epa-1 may be a strain-specific marker for activated M phi in the mouse, as well as an inducible histocompatibility antigen in vivo.

MHC epitopes of KS and Dd restrict the same population of cytolytic T lymphocytes

When A. SW (H-2S) mice are immunized with B10.S (H-2S) epidermal cells, cytolytic T lymphocytes are evoked that efficiently lyse B10.D2 (H-2d) as well as B10.S target cells. Immunogenetic analysis of this apparent H-2-unrestricted killing revealed that the most plausible explanation was a sharing of an H-2-restricting epitope by H-2KS and H-2Dd molecules.