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Primary T-cell responses to minor alloantigens. II. Analysis of accessory cell requirements for the development of cytotoxic T lymphocytes.

The accessory cell requirements of cytotoxic T-lymphocyte (CTL) responses directed at multiple minor alloantigens are examined using a short-term, combined in-vivo and in-vitro protocol. The development of cytotoxic activity in vitro from T cells sensitized in vivo requires low-density accessory cells derived from the immunizing strain which have to be H-2 compatible with the responder population. The accessory activity of these cells can be by-passed by interleukin-2 (IL-2)-containing supernatant. Since IL-2 is a product of helper T (Th) cells secreted upon activation by antigen recognized in context of self H-2 and is known to stimulate antigen-activated cytotoxic T-lymphocyte precursors (CTL-P) non-specifically to effector CTL function, the results indicate that accessory cells interact in an H-2 restricted fashion with helper rather than cytotoxic T-lymphocyte precursors. The low-density accessory cells active in this system do not express Fc receptors (FcR) and are present in both the adherent and non-adherent fractions of spleen or lymph nodes.