CD4 and infection: Expansion of IL-17-producing cells (either CD4+ T cells, CD8+ T cells or macrophages) and related cytokines (IL-17, IL-22 and IL-23) has been observed in P. vivax natural infections [59] as well as P. berghei, P. chabaudi and P. fragile animal models [60-62], where these interleukins have been shown to reduce parasite intensity and protect against fatal outcomes [59-61].