Inhibitory activity of anti-interleukin-4 and anti-interleukin-10 antibodies on Toxoplasma gondii proliferation in mouse peritoneal macrophages cocultured with splenocytes from infected mice

Cocultures of splenocytes from Toxoplasma gondii-immunized mice or from naive mice, separated by a transwell membrane from naive macrophage layers, induced a decrease in T. gondii proliferation in macrophages in comparison with cultures without splenocytes or cocultures with splenocytes from infected mice. Interleukin 4 (IL-4) and IL-10 levels increased in cocultures of splenocytes from infected mice with naive macrophages. In contrast, the levels of these cytokines decreased in cocultures with splenocytes from immunized mice. No correlation was found between the release of interferon-gamma (IFN-gamma) and the inhibition of parasite multiplication. Cocultures with splenocytes from immunized mice induced an increase in tumor necrosis factor-alpha (TNF-alpha) levels. In contrast, in cocultures with splenocytes from infected mice, TNF-alpha production decreased. In cocultures with splenocytes from infected mice, T. gondii proliferation in macrophages was neutralized by anti-IL4 or anti-IL10 antibodies and was associated with increased TNF-alpha production. Moreover, this study demonstrates the significant combined effect of IL-4 and IL-10 on the down-regulation of macrophage-effector functions. A soluble positive signal was given by splenocytes to induce the production of TNF-alpha by macrophages. This signal was inhibited by IL4 and IL10. This process is biologically relevant in the regulation of T. gondii proliferation.