HLA-DR-restricted cytotoxicity of cytomegalovirus-infected monocytes mediated by Leu-3-positive T cells.

Mononuclear leukocytes from 14 cytomegalovirus (CMV)-seropositive and six CMV-seronegative normal healthy donors were treated with soluble CMV antigen for 5 days to generate cytotoxic T lymphocyte (CTL) activity. CMV-antigen-stimulated lymphocytes from CMV-seropositive but not CMV-seronegative donors lysed autologous peripheral blood monocyte targets infected with CMV in 13 of 14 donors (mean percentage of virus-specific lysis = 19.0 +/- 4.5%, effector to target ratio of 50:1). Freshly donated, unstimulated lymphocytes displayed little or no lysis of CMV-infected monocytes. Lysis was virus specific in that CMV-stimulated CTL did not kill herpes simplex virus-infected monocytes. The mean level of lysis of CMV-infected autologous targets was equivalent to that of HLA-DR-matched targets (20.0 +/- 8.0%), and was significantly greater than that of HLA-A/B-matched targets (6.3 +/- 2.5%, p less than 0.035) and HLA-mismatched targets (3.3 +/- 2.5%, p less than 0.01). Enrichment for T cell subsets with the use of selective depletion methods with monoclonal antibodies showed that CTL activity against autologous and HLA-DR-matched allogeneic targets was present predominantly in Leu-3-positive T lymphocytes. These results show for the first time that short term stimulation of heterogeneous lymphocytes from CMV-seropositive donors with CMV antigen can generate CMV-specific, Leu-3-positive CTL that are primarily restricted in their activity to autologous and class II, HLA-DR-matched targets. Our findings suggest a role for Leu-3-phenotypic CTL in immunity to CMV, and provide a model for analysis of this antiviral effector function during immunodeficient states.