Wheat germ agglutinin decreases expression of the T8 antigen on human peripheral mononuclear cells

We examined dynamics of expression of the human T-suppressor specific antigen, T8, following interaction of peripheral lymphocytes with wheat germ agglutinin (WGA). Cells were incubated at 37 degrees C with or without WGA (15 micrograms/ml) for 18 hrs, washed sequentially with N-acetylglucosamine (to remove bound WGA) and plain medium, then analyzed by flow cytometry for binding of lectins and monoclonal antibodies OKT8(T-suppressor specific) and OKT3 (pan-T specific). WGA pretreatment induced an overall 65% reduction in WGA binding and concomitant 30% reduction in percentage of T8+ cells. Furthermore, residual T8+ cells showed 50% reduction in T8 expression. Taking into account reductions in both percentages of T8+ cells and also antigen densities, WGA reduced T8 expression by greater than 60% overall. By contrast, binding of OKT3 and the lectins, concanavalin A (con A) and Ricinus communis agglutinin (RCA-I), was unaffected by WGA. The decreased T8 expression could not be explained by residual cell bound WGA and was fully reversible within 48 hours of removal of cells from WGA-containing medium. Therefore, WGA caused downregulation of T8 antigen expression. The effect of WGA was time- and concentration-dependent. Downregulation did not occur at 4 degrees C nor in the presence of azide, thereby demonstrating a requirement for cellular metabolism. The data suggest that WGA may bind to the T8 antigen, and they provide the possibility that similar downregulation of T8 by WGA may underlie certain of the in vitro immunoregulatory effects of this lectin.