Serum from Entamoeba histolytica-infected gerbils selectively suppresses Tcell proliferation by inhibiting interleukin-2 production

Suppression of T and B cell responses during invasive amebiasis may be seru m mediated. The mechanism of serum-mediated suppression of spleen cell lymp hoproliferation from gerbils with amebic liver abscess was examined. Compar ed with uninfected gerbil serum (10%), serum samples collected at days 10, 30, and 60, but not at day 20 after infection, augmented both concanavalin A (Con A; T cell mitogen)- and lipopolysaccharide (LPS; B cell mitogen)indu ced proliferation of homologous spleen cells. Only day 20 serum (>5%) inhib ited Con Abut not LPS-induced proliferation of spleen cells from uninfected gerbils, The suppressive mechanism was independent of nitric oxide and pro staglandin but involved reduced interleukin (IL)-2 production. Addition of exogenous IL-2 reversed the suppressive effect of day 20 serum on Con A-sti mulated proliferation. These results identify a mechanism whereby serum may contribute to transient suppression of T cell responses during Entamoeba h istolytica infections.