Human T4+ and T8+ cytotoxic T lymphocyte clones directed at products of different class II major histocompatibility complex loci.

Abstract

Abstract Three human CTL clones, JR-2-2, JR-2-19, and HG-31, which recognized antigens associated with class II products of the major histocompatibility complex (MHC), were analyzed. The clones were obtained by limiting dilution of T cell cultures of two different donors JR (HLA Aw23,w29; B7,7;DR5) and HG (HLA A2,w23;B40,w44;DRw6,7) stimulated three times with cells of the lymphoblastoid cell line JY (HLA A2;B7;DR4,w6). The activity of all three CTL clones could be blocked by a rabbit anti-human la antiserum, whereas this antiserum did not block the activity of two class I MHC specific CTL clones, JR-2-16 and HG-31, which were included in this study as controls. The activity of JR-2-2, JR-2-19, and HG-38 could not be blocked by a monoclonal anti-HLA-A, B and C antibody W6/32. In contrast W6/32 inhibited strongly the activity of the class I MHC specific CTL clones. CTL clone JR-2-2 seemed to recognize a class II antigen different from the one recognized by JR-2-19 and HG-38, because the activity of JR-2-2 could be inhibited by the monoclonal antibodies Q5/6 and Q5/13, which reacted with determinants on HLA-DR, whereas these antibodies did not block the activity of the CTL clones JR-2-19 and HG-38. The activity of these latter CTL clones was blocked by SPV-L3, a monoclonal reagent that recognizes a monomorphic determinant present on HLA-DC. SPV-L3 did not block the activity of the class I MHC specific clones nor that of JR-2-2. These findings suggest that JR-2-2 recognized HLA-DR, whereas JR-2-19 and HG-38 interacted with determinants on HLA-DC. A panel study with HLA-typed EBV-transformed B blasts used as target cells revealed that JR-2-2 recognized an antigen predominantly associated with HLA-DRw6. CTL clone JR-2-19 only lysed target cells expressing either HLA-DR2 or DRw6, suggesting that JR-2-19 recognized a determinant present on DC-1. Both JR-2-2 and JR-2-19 killed Daudi cells, excluding a role for class I MHC in the cytotoxic activity of these two CTL clones. In contrast to JR-2-2, clone JR-2-19 killed normal macrophages expressing DRw6 only to a low extent; however, JR-2-19 was able to kill HLA-DRw6+ EBV− lymphoma cells, excluding the possibility that this clone recognized an EBV antigen in the context of class II MHC antigens. The target specificity of HG-38 could not be correlated with a known serologically defined HLA specificity. In view of the finding that CTL clone JR-2-2 recognizes a class II MHC product, it was remarkable to observe that JR-2-2 was T3+ T4− T8+. JR-2-19 and HG-38 expressed T4, but lacked T8. The implications of these observations—that the T4 and T8 antigens are markers for the specificity of T cells instead of being functional markers—are discussed.