CD4 T cells play critical roles in mediating adaptive immunity to a variety of pathogens. They
are also involved in autoimmunity, asthma, and allergic responses as well as in tumor
immunity. During TCR activation in a particular cytokine milieu, naive CD4 T cells may
differentiate into one of several lineages of T helper (Th) cells, including Th1, Th2, Th17, and
iTreg, as defined by their pattern of cytokine production and function. In this review, we
summarize the discovery, functions, and relationships among Th cells; the cytokine and …