The helper T cells can be Th1, Th2, Th9, Th17, or Th22 cells, depending upon the pathogen and types of cytokines present in the cellular microenvironment. They are responsible for responding to both intracellular as well as extracellular pathogens and have also been found to be involved in various diseases.
CD4 T helper (Th) cells play a central role in orchestrating adaptive immune responses to invading pathogens through their ability to differentiate into specialized effector subsets. Part of this customized response requires the development of T follicular helper (Tfh) cells, which provide help to B cells for the generation of germinal centers (GCs) and long-term protective humoral responses. Although initially viewed as terminally differentiated, we now recognize that Th cell subsets, including Tfh cells, display substantial flexibility and overlap in their characteristics. In this review, we highlight advances in our understanding of Tfh cell development, cytokine production, and the potential plasticity that allows Tfh cells to possess characteristics of other effector Th cell populations.
CD4 T helper cells are the primary orchestrators of the adaptive immune response, mediating a variety of cellular and humoral responses against pathogens and cancer. Although they lack any capacity to directly kill or engulf pathogens, they are powerful activators of effector cells such as macrophages, cytotoxic T cells, and B cells. On the other hand, regulatory T cells (Tregs) are potent suppressors of the immune response important in limiting the immune reaction. Recent advances have led to the discovery of a diverse set of T helper subsets, each with unique functions.