IL6 and infection: Compared to the peritoneal macrophages from mice injected with nRBCs, the reactivity of macrophages from mice infected either with P. yoelii 17XL or 17XNL was enhanced at one, three and five days post infection, as both inflammatory cytokines TNF and IL-6 released by macrophages stimulated with pRBC lysate were much higher in either strain infected mice (Figure 2).