T Cell Antigen Recognition: Key Steps in Adaptive Immune Response Activation

Antigen recognition by T cells: T cell activation

~ The required secondsignal is provided via CD80/86 – CD28 that induces the expression of CD154 first and CD152 later on. Next T Cell CD154 binds with CD40 on APCs. These APC – T cell interactions induce the activation and proliferation of downstream effector cells.

Antigen recognition by T cells is a crucial aspect of the adaptive immune response. T cells recognize foreign antigens presented on the surface of antigen-presenting cells (APCs) such as dendritic cells, macrophages, and B cells. The T cell receptor (TCR) plays a central role in antigen recognition by T cells and is composed of an alpha and beta chain or, less commonly, a gamma and delta chain.

Once a TCR recognizes its specific antigen, a series of signaling events occurs that ultimately leads to T cell activation and proliferation. This process is initiated by the engagement of the TCR with the antigen-presenting cell, which triggers the recruitment of a coreceptor molecule, CD4 or CD8, on the T cell surface. This binding, together with interactions between various costimulatory molecules, provides the necessary signals for T cell activation.

Activated T cells undergo clonal expansion, with the initial T cell dividing and giving rise to a population of effector T cells that are specific for the presented antigen. These effector T cells are responsible for directly attacking pathogen-infected cells or producing cytokines that mediate the immune response.

In conclusion, T cell recognition of foreign antigens through TCRs and coreceptors leads to T cell activation and subsequent proliferation, ultimately generating effector T cells capable of mounting an appropriate immune response.

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