| Abstract: | The T3-Ti complex appears to play a central role in the activation of T cells by antigens and mitogens. Wheat germ agglutinin (WGA) is a unique lectin which inhibits T cell proliferation induced by mitogens, but it also induces marked IL 2 production by peripheral blood T cells. The pattern of responses induced by WGA suggests that this lectin may use a different mechanism of T cell activation other than the mechanism employed by the common T cell stimulants. We first investigated the production of IL 2 by Jurkat cells (E6-1) stimulated with WGA, before and after modulation of the surface T3-Ti complex. IL 2 production was markedly reduced after modulation of the T3 antigen from the cell surface when these cells were stimulated with PHA. In contrast, little change was observed in WGA-induced IL 2 production after modulation. Furthermore, we examined the effect of WGA on a T3-mutant of E6-1 cells (T3.1) which does not produce IL 2 in response to PHA or PHA plus PMA. WGA-stimulated T3.1 cells produced a significant amount of IL 2 with or without added PMA. In addition, a small but consistent rise in intracytoplasmic free calcium was observed when these cells were stimulated with WGA. These results demonstrate the presence of an alternative mechanism of T cell activation independent of the T3-Ti complex. |
