helper T cell

helper T cell,

a T lymphocyte that promotes the immune response of other lymphocytes to foreign antigens by releasing soluble proteins called helper factors. It is essential in determining B cell antibody class switching and maximizing bacteriocidal activity of phagocytes, as well as in growth and activation of cytotoxic T cells. Helper T cells have no cytotoxic or phagocytic activity. See also T cell.

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helper T cell

Helper T lymphocyte, CD4+ T cell Immunology A subset of T lymphocytes with the antigen determinant CD4, which are presented with a foreign antigen in the context of both a self MHC class II antigen and IL-1; once immune recognition or response occurs, HTCs produce various cytokines–eg, IFN-γ, IL-2 and osteoclast-activating factor, which are critical in hematopoietic differentiation, collagen synthesis, and antibody formation; HTCs play a central role in normal and pathologic immune responses by secreting various cytokines–eg, IL-2, IFN-γ, and TNF are involved in cell-mediated immunity Types Type 1–produces IL-2 and IFN-γ; ↑ in infectious granulomatous processes; type 2–produces IL-4 and IL-5; ↑ in atopic disorders, lepromatous leprosy, visceral leishmaniasis and as a clonal expansion in hypereosinophilic syndrome. See CD4, Flow cytometry, Suppressor cells, T cells.