title: Differential requirements for activation and growth of unprimed cytotoxic and helper T lymphocytes.
abstract: The requirements for activation and growth of T lymphocytes capable of mediating either cytolytic activity or help to B lymphocytes were studied in unprimed splenic T cell populations. The selectivity of expression of Lyt-2 antigens, the reactivity to soluble concanavalin A (Con A), to partially purified interleukin 2 (IL 2, T cell growth factor[s]) and to lectin-pulsed macrophages (M phi) were used in this analysis. Lectin-dependent cytotoxicity assays and a novel method that allows for the detection of all effector helper cells, regardless of their clonal specificities, were used for the functional identification of the responding T cells. The results show a marked contrast between cytolytic and helper T cells in their growth and activation requirements. Thus, while Lyt-2+ cytotoxic T lymphocyte precursors grow exponentially in IL 2 after a short pulse with soluble Con A in the absence of accessory cells, Lyt-2- helper cell precursors completely fail to proliferate under the same conditions and require the continuous presence of lectin-pulsed M phi for significant growth. Furthermore, addition of IL 2 to M phi-stimulated cultures of Lyt-2- cells has no effect. T cells which produce IL 2 have the same growth characteristics as helper cells. In both cases, effector helper functions could be expanded more than 10-fold on a per cell basis by a 5-day-culture period under those growth supporting conditions. The development of effector helper functions, however, was strongly inhibited by the presence of Lyt-2+ T cells.
mesh_terms: D000818:Animals; D002455:Cell Division; D003208:Concanavalin A / Q000494:pharmacology*; D007376:Interleukin-2 / Q000096:biosynthesis / Q000494:pharmacology*; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008264:Macrophages / Q000502:physiology; D051379:Mice; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000502:physiology*; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology / Q000502:physiology*
chemical_list: D007376:Interleukin-2; D003208:Concanavalin A