How is antigen presentation carried out in immune cells?

Antigen presentation is a crucial process in the immune response, allowing immune cells to recognize and respond to pathogens. One primary method of antigen presentation involves receptor-mediated endocytosis, where immune cells, such as dendritic cells, macrophages, and B cells, uptake antigens through specific receptors on their surface. After internalization, these antigens are processed and then complexed with Major Histocompatibility Complex (MHC) class II molecules. This MHC-antigen complex is then transported to the cell surface, where it can be recognized by T-helper cells, initiating a wider immune response.

This process emphasizes the specificity and efficiency of immune cells in dealing with antigens. It enables the body to mount a tailored response to specific pathogens and is an essential step in adaptive immunity. MHC class II is particularly important as it presents exogenous antigens that have been taken up from the extracellular environment, informing T cells about what the immune system encounters outside the cells.

Other methods, such as phagocytosis, do contribute to the intake of antigens, but they are not solely responsible for antigen presentation. Passive diffusion does not effectively promote the uptake of large molecules such as proteins, and direct contact with antibodies does not facilitate the processing and