T lymphocyte responses to non-H-2 histocompatibility antigens. I. Role of Ly-1⁺2⁺ T cells as cytotoxic effectors and requirement for Ly-1⁺2⁺ T cells for optimal generation of cytotoxic effectors

Cytotoxic effector T cells specific for non-H-2 histocompatibility (H) antigens were examined for phenotypic expression of lymphocyte differentiation (Ly) antigens. Virtually all H-Y-specific cytotoxic effectors generated in mixed lymphocyte culture were Ly-1⁺2⁺ T cells. H-3-specific effectors comprised both Ly-1⁺2⁺ and Ly-1^-2⁺ T cells. However, cytotoxic effectors specific for multiple non-H-2 H antigen-specific effectors required an interaction between Ly-1⁺2^- and Ly-1^-2⁺ T cells. These observations suggest that the identity of the target H antigen in part determines the Ly type of responsive T cells. Our observations suggest that 2 alternative pathways of T cell response exist for non-H-2 H antigens. The first pathway involves an interaction between Ly-1⁺2^- helper T cells and Ly-1^-2⁺ cytotoxic effector precursors. The 2nd pathway simply involves the response of Ly-1⁺2⁺ T cells proliferating and generating H antigen-specific cytotoxic effectors.