title: Secretion of a suppressor cell-inducing factor by an interleukin 3-dependent cell line with natural cytotoxic activity. II. Range, potency, and kinetics of suppressive activity.
abstract: We have shown previously that the interleukin 3 (IL 3)-dependent, M1-A5 cell line has natural cytotoxic (NC) activity and secretes a small molecular weight factor which activates suppressor cells capable of inhibiting the in vitro generation of antibody forming cells (PFC). In this paper, we show that the M1-A5 cells are capable of suppressing the generation of both PFC and cytotoxic T cells (CTL) as well as the proliferative response in a mixed lymphocyte reaction (MLR). Very little suppression of Concanavalin A (Con A)-stimulated proliferation is seen. Suppression is seen with as few as 10(2) M1-A5 cells, a 10(-4) dilution of a cell-free supernatant from the M1-A5 cells, or as few as 10(4) suppressor cells activated by the suppressor cell inducing factor (SIF) secreted by the M1-A5 cell line. Kinetic studies show that, in all cases, the cells or suppressive factors must be present in the initial 24 to 48 h of the culture for significant suppression. In contrast, a second IL 3-dependent cell line FDC-P1 is directly suppressive, but this suppression is clearly due to a different mechanism, since cell-free supernatants are not inhibitory and do not activate suppressor cells.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003208:Concanavalin A / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000145:classification / Q000276:immunology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects*; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects* / Q000378:metabolism
chemical_list: D007377:Interleukin-3; D003208:Concanavalin A