Antigens are molecules or molecular structures that are foreign to the body and generally induce an immune reaction in the form of the production of antibodies against them ¹. The uptake of exogenous antigens is primarily mediated by phagocytosis via Antigen Processing Cells (APCs) like macrophages, dendritic cells, etc. ¹. The antigenic proteins are processed to peptides in endolysosomal compartments to be loaded on MHC-II molecules biosynthesized in the endoplasmic reticulum ³. The peptide/MHC-II complexes leave the endosomal antigen-processing compartments to be transported to and inserted into the plasma membrane for T cell recognition by CD4+ T cells ³.
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