Understanding the Role of Processed Exogenous Antigens in Immune Activation: An Overview

b. From processed exogenous antigens

Processed exogenous antigens refer to foreign substances that have entered the body from outside and are being processed by antigen-presenting cells (APCs)

Processed exogenous antigens refer to foreign substances that have entered the body from outside and are being processed by antigen-presenting cells (APCs). APCs are specialized immune cells, such as dendritic cells, macrophages, and B cells, that capture, process, and present antigens to other immune cells.

When a foreign substance enters the body, it is engulfed by an APC through a process called phagocytosis. The antigen is then broken down into smaller fragments within the APC’s intracellular compartments called endosomes and lysosomes. This process of antigen degradation is known as antigen processing.

Once the antigen is processed, it is loaded onto major histocompatibility complex (MHC) molecules within the APC. MHC molecules are proteins that serve as platforms for antigen presentation. There are two types of MHC molecules involved in antigen presentation: MHC class I and MHC class II.

Processed exogenous antigens are presented on MHC class II molecules. MHC class II molecules are primarily found on APCs and are responsible for presenting antigens to helper T cells. The processed antigen-MHC complex is then transported to the surface of the APC, where it is displayed for recognition by T cells.

Helper T cells have specialized receptors called T cell receptors (TCRs) that can recognize specific antigens. When a TCR binds to the processed antigen-MHC complex on the APC, it triggers a cascade of immune responses, including the activation and proliferation of T cells. These activated T cells can then coordinate specific immune reactions to eliminate the invading pathogen.

In summary, processed exogenous antigens are taken up by APCs, broken down into smaller fragments, loaded onto MHC class II molecules, and presented on the surface of the APC to activate helper T cells. This immune response is crucial for eliminating foreign pathogens and maintaining overall immune homeostasis in the body.

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