HLA-DR-antigen-associated restriction of EBV-specific cytotoxic T-cell colonies

Abstract

EBV-specific cytotoxic T cells can be generated in vitro in a secondary response. Several previous studies with bulk cultures provided evidence that cytotoxicity was restricted by HLA-A,B-related antigens. In the present family study, the EBV-specific cytotoxic T-cell response of a normal EBV-seropositive donor was analysed in detail by T-cell colony formation. Peripheral blood mononuclear cells were stimulated by the gamma-irradiated autologous lymphoblastoid cell line (LCL) and 3 days later seeded into agarose. Colonies were harvested, amplified by addition of interleukin-2 (IL-2), and analysed for T-cell markers and specificity in ⁵¹Cr-release assays. Twenty-two colonies were studied: all colonies were OKT3⁺, five were predominantly OKT4⁺, 9 were OKT8⁺ and 8 were mixtures. As expected from previous work, the OKT8⁺ colonies were cytotoxic for the autologous LCL target and cytotoxicity was blocked by monoclonal antibody (W6/32) to the non-polymorphic determinants of HLA-A,B,C antigens. Significantly, the OKT4⁺ colonies tested also showed specific cytotoxicity, but lysis of the autologous LCL was blocked by the monoclonal antibody (OKIa1) to the non-polymorphic determinants of HLA-DR antigens. Two interesting patterns of specificity were seen in cytotoxicity tests on sibling LCL targets. In one pattern, targets bearing the A11, B5, DR7 haplotype were lysed, while those bearing the A1,B8,DR3 were not, indicating haplotype preference. In the other pattern, there was lysis of the autologous cell line but not of the sibling targets. These results including HLA-DR-associated restriction, haplotype preference and strict self-preference, further illustrate the complexity of the EBV-cytotoxic T-cell response.