T helper cell type 1 (Th1 cell)

T helper cell type 1 (**Th1 cell**) is a specialized subset of CD4+ T lymphocytes characterized by the production of cytokines such as interferon-gamma (IFN-γ), interleukin-2 (IL-2), and tumor necrosis factor-beta (TNF-β)[1][3][7]. Th1 cells play a central role in orchestrating the cell-mediated immune response, particularly in the defense against intracellular pathogens like viruses, intracellular bacteria (e.g., *Mycobacterium tuberculosis*, *Leishmania major*), and certain protozoa[3][4][6]. Th1 cells activate macrophages, promote phagocytosis, and aid the maturation of cytotoxic T lymphocytes (CTLs). Differentiation to the Th1 phenotype is driven by cytokines (notably IL-12) and transcription factors such as T-bet[6][7]. Th1 responses are essential for effective immunity against infections but, if dysregulated, are implicated in the pathogenesis of several autoimmune diseases (e.g., type 1 diabetes, psoriasis, inflammatory bowel disease)[4][7]. Th1 cells are not a single molecule, receptor, or canonical drug target but rather a differentiated cell population, so are not considered a direct therapeutic target such as a receptor or enzyme[1][3][7]. Drugs may, however, target the cytokines they produce or the pathways regulating their activation. Overactivation or persistent Th1 responses can contribute to tissue injury, chronic inflammation, and autoimmunity[4][7]. Key identifying biomarkers include the cytokines IFN-γ, IL-2, and the transcription factor T-bet[1][6].

Other names

Type 1 helper T cellTh1 lymphocyteT helper 1 cell