Effector functions of helper T cells.

We have reviewed the basic pathways of postthymic development of CD4 T cells (Th) and attempted to pinpoint the regulatory events that lead to the formation of functional effectors and/or the polarization of their patterns of cytokine secretion, which endow CD4 T cells with distinct functions. One finding of these studies is that the major role of naive cells is not to carry out regulatory functions, but rather to serve as precursors of the effector and memory populations. We have shown not only the particularly impressive capacity of effector populations generated in vivo and in vitro to secrete cytokines upon restimulation, but also the impressive helper function of both primary and memory effectors, which make Th2-like patterns of cytokines.