CD4-positive helper T cell CALOHA:TS-1146 CD4-positive helper T-lymphocyte A CD4-positive, alpha-beta T cell that cooperates with other lymphocytes via direct contact or cytokine release to initiate a variety of immune functions. The CD4-positive helper T cells are a subpopulation of T lymphocytes, which are part of the adaptive immune system. These cells play a vital role in establishing and maximizing the capability of the immune system to combat infections. Like all T lymphocytes, CD4+ helper T cells are uniquely characterized by the expression of a T-cell receptor (TCR) complex on their cell surface. The subset of CD4+ cells express the CD4 glycoprotein on their cell surface that serves as a co-receptor for the T-cell receptor. The CD4 co-receptor enables these cells to interact with antigen-presenting cells and perform their influential role in adaptive immune response. CD4+ helper T cells are primarily responsible for assisting other cells in the immunological processes. This involves recognition, interaction, and processing of antigens. Once an antigen-presenting cell presents a foreign antigen such as peptides derived from pathogens or transformed cells to the CD4+ helper T cell, it becomes activated, proliferates, and differentiates into subtypes such as Th1, Th2, Th17, or Treg, each with a specific role in the immune response. Th1 cells produces various cytokines. including IFN‐γ, IL-2 and TNF-β, and aid cell-mediated immune responses against intracellular pathogens. Th2 cells produce IL-4, IL-5 and IL13 and assist in antibody-mediated immune responses. Th17 cells release IL-17 and convey protective immunity against extracellular bacteria and fungi as well as contributing to inflammation and autoimmunity, while Treg cells are immunosuppressive cells and maintain immune homeostasis and provide tolerance to self-antigens. Finally, follicular T helper (Tfh) cells are thought to help B cells build up antibody responses by assisting germinal center formation, affinity maturation, and possibly immunoglobulin class switch recombination In addition to their critical role in immune response, CD4+ helper T cells are notably the main target of HIV infection, where the virus depletes the number of these cells, resulting in the deterioration of the immune system, characterized in the progression to AIDS. Thus, the presence and functionality of CD4+ helper T cells are not only necessary for a healthy immune response but also crucial in the context of immunodeficiency diseases. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) CD4-positive helper T-cell CD4-positive T-helper cell FMA:70572 https://cellxgene.cziscience.com/cellguide/CL_0000492 CD4-positive helper T lymphocyte CD4-positive, alpha-beta T cell Homo sapiens