Secretes cytokines that help B cells make antibodies or that activate pathogen-infected macrophages
The cells responsible for secreting cytokines that help B cells make antibodies or activate pathogen-infected macrophages are T helper cells, specifically a subset called T follicular helper (Tfh) cells
The cells responsible for secreting cytokines that help B cells make antibodies or activate pathogen-infected macrophages are T helper cells, specifically a subset called T follicular helper (Tfh) cells.
Tfh cells are a specialized population of CD4+ T cells that play a crucial role in promoting antibody-mediated immune responses. When a pathogen invades the body, antigen-presenting cells (APCs) such as dendritic cells capture and process the pathogen’s antigens. These antigens are then presented on the surface of APCs along with major histocompatibility complex II (MHC II) molecules.
When Tfh cells encounter these APCs displaying antigen-MHC II complexes, they interact through the recognition of specific antigens by the T cell receptor on the surface of Tfh cells. This interaction is further strengthened by the binding of co-stimulatory molecules between the APC and Tfh cells.
Once activated, Tfh cells undergo several changes that help them guide and support B cells in producing antibodies. The main mechanism by which Tfh cells promote antibody production is through the secretion of cytokines, which are small proteins that act as signaling molecules in the immune system.
Tfh cells primarily secrete two types of cytokines involved in antibody production: interleukin-4 (IL-4) and interleukin-21 (IL-21). IL-4 plays a critical role in the class switch recombination of B cells, guiding them to switch from producing IgM antibodies to isotypes such as IgG, IgE, or IgA, which have different effector functions. By secreting IL-4, Tfh cells help B cells generate a diverse range of antibodies suitable for various immune functions.
IL-21, on the other hand, is a potent stimulator of B cell proliferation, differentiation, and antibody production. Tfh cells produce IL-21 to provide growth and survival signals to B cells, leading to their differentiation into plasma cells, which are the antibody-secreting cells.
Additionally, Tfh cells can release other cytokines such as interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) to activate macrophages that have been infected by pathogens. These cytokines enhance the phagocytic and killing activities of macrophages, aiding in the clearance of pathogens from the body.
In summary, Tfh cells secrete cytokines like IL-4 and IL-21, which play vital roles in supporting B cells to make antibodies and promoting the activation of pathogen-infected macrophages. Through these mechanisms, Tfh cells contribute significantly to the generation of effective immune responses against invading pathogens.
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