1. T cell differentiation
T cell differentiation. Naïve CD4+ T cells differentiate into one of several T helper (Th) cell lineage based on signals from innate immune cells induced by antigenic and inflammatory stimuli as presented by activated DCs. The resultant products of differentiated T cells subsequently help tailor the immune response to various encountered antigen scenario. Th cell differentiation is classically regarded as a dichotomy between two main cell types, termed Th1 and Th2. Th1 cells produce IFN-γ as the signature cytokine and are predominantly involved in cell-mediated immunity against intracellular pathogens. In contrast, Th2 cells do not produce IFN-γ and instead produce IL-4, IL-5, and IL-13. Th2 cells are effective activators of B cell proliferation and antibody production, mediating humoral immunity essential for the eradication of extracellular pathogens as well as mediating allergic type of inflammation. Th17 cells have been described as a distinct Th subset characterized by the production of IL-17A, IL-17F, and IL-22, contributing to host defence against extracellular pathogens particularly on mucosal surfaces, as well as in the pathogenesis of autoimmune diseases. Recently, more Th cell subsets have been described such as Th9 and Th22 cells that participate in allergic type of immune responses. Other stimuli cause CD4+ T cells to become regulatory T (Treg) cells that help dampen immune responses. Other stimuli allow CD4+ T cells to reside in lymph nodes, differentiate into follicular helper T (Tfh) cells and provide help to B cells. The various Th subsets require activation of specific master regulator transcription factors such as T-bet, GATA-3, RORγt, Bcl-6, and Foxp3 as well as various STAT molecules for their differentiation as indicated in the diagram. Bcl-6, B cell lymphoma-6; Foxp3, forkhead box p3; ROR, retinoid-related orphan receptor; AHR, aryl hydrocarbon receptor; STAT, signal transducer and activation of transcription.
Source: Innate and Adaptive Immunity in the Lung, Fishman's Pulmonary Diseases and Disorders, 5e
Citation: Grippi MA, Elias JA, Fishman JA, Kotloff RM, Pack AI, Senior RM, Siegel MD. Fishman's Pulmonary Diseases and Disorders, 5e; 2015 Available at: Accessed: November 02, 2017
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