Glycoinositolphospholipids purified from Trypanosoma cruzi stimulate Ig production in vitro

We have investigated the effects of glycoinositolphospholipid (GIPL) purified from Trypanosoma cruzi on murine B cell activation. The GIPL neither stimulated any proliferative response by itself, nor affected the blastogenesis induced by surface IgD cross-linking or LPS. On the other hand, the GIPL significantly stimulated both low and high density B cells to secrete IgM in vitro. The GIPL induced B cells to produce IgM when added in the presence of either the surface Ig cross-linker, anti-delta-dextran, or a combination of IL-4 and IL-5. The T. cruzi-derived GIPL also stimulated Ig class switch to IgG1 in cultures stimulated with GIPL, IL-4, and IL-5. The IgG1 secretion was comparable to that induced by LPS plus IL-4. Production of IgG3 was also detected and the GIPL also potentiated the IgG3 production induced by LPS. The stimulatory effect of the T. cruzi-derived GIPL was mediated mainly by its oligosaccharide moiety. This isolated fraction induced a potent IgM secretory response, compared with a much lower response induced by the isolated GIPL ceramide. Taken together, our data suggest that the stimulatory effect of the T. cruzi-derived GIPL on B cell activation could play a role on the conspicuous Ig production observed during infection of the host with T. cruzi.