T-helper lymphocytes (Th cells)

T-helper lymphocytes (Th cells), also known as CD4+ T cells, are a critical component of the adaptive immune system. They express the surface protein CD4 and recognize antigens presented by MHC class II molecules on antigen-presenting cells (APCs). Th cells are essential for coordinating almost all adaptive immune responses by activating other immune cells, including B cells, cytotoxic T cells, and macrophages, through cytokine release and direct cell interactions. They differentiate into various subtypes (Th1, Th2, Th17, Tfh, Treg) depending on the cytokine environment during activation, allowing for tailored responses against different pathogens or for immune regulation. Their function is crucial in defending against infectious diseases, but their dysregulation is implicated in autoimmune diseases and allergies. HIV primarily targets these cells, leading to severe immunodeficiency. Modulating T-helper cell responses is an important strategy in developing therapies for various immunological conditions.

Other names

CD4+ T cellsCD4-positive cells