For instance, distinct and specialised CD4+ T cell subsets have been implicated in immunity against viral or intramacrophagocytic (Th1), parasitic (Th2) and fungal (Th17) infections, as well as regulating B-cell differentiation/humoral immunity (Tfh) and immune regulation/homeostasis (Tregs)3, 20. This evidence concerns the gene CD4 and infection.