Answer :
The activation of T cells following infection at a mucosal surface involves antigen recognition, T cell activation, clonal expansion, differentiation into effector T cells, and migration to the site of infection. This coordinated process helps eliminate pathogens and promote an effective immune response to protect the mucosal surfaces.
When a pathogen infects a mucosal surface, such as the respiratory or gastrointestinal tract, several events occur during the activation of T cells as part of the immune response.
Antigen Recognition: T cells play a crucial role in recognizing and responding to specific antigens presented by antigen-presenting cells (APCs) such as dendritic cells. During infection, APCs encounter the pathogen and capture its antigens. The antigens are then processed and presented on the surface of the APCs using major histocompatibility complex (MHC) molecules.
T Cell Activation: T cells have T cell receptors (TCRs) on their surface that recognize the specific antigen-MHC complex. When a TCR on a T cell binds to the antigen-MHC complex, it triggers a series of signaling events, leading to T cell activation. Co-stimulatory signals from APCs are also required for full activation of T cells.
Clonal Expansion: Upon activation, T cells undergo clonal expansion, resulting in the rapid proliferation of antigen-specific T cells. This expansion ensures a robust immune response against the pathogen. Clonal expansion is driven by cytokines released by APCs and other immune cells.
Differentiation: During clonal expansion, T cells differentiate into effector T cells with specific functions. In the case of mucosal infections, T helper 1 (Th1) cells and cytotoxic T lymphocytes (CTLs) are crucial. Th1 cells secrete cytokines such as interferon-gamma (IFN-gamma), which activate macrophages and enhance their antimicrobial activity. CTLs, on the other hand, recognize and kill infected cells directly.
Migration to the Infection Site: Activated T cells migrate to the mucosal site of infection to exert their effector functions. Chemokines and adhesion molecules guide T cell trafficking to the infected tissue. Once at the site, effector T cells can eliminate infected cells and coordinate the immune response to control the infection.
In summary, the activation of T cells following infection at a mucosal surface involves antigen recognition, T cell activation, clonal expansion, differentiation into effector T cells, and migration to the site of infection. This coordinated process helps eliminate pathogens and promote an effective immune response to protect the mucosal surfaces.
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