antigenpresentációval

Antigenpresentációval, often translated as antigen presentation, is a crucial process in the adaptive immune system. It refers to the display of antigens by specialized cells called antigen-presenting cells (APCs) to lymphocytes, primarily T cells. This presentation is essential for initiating an effective immune response against pathogens and abnormal cells.

Antigen-presenting cells, such as dendritic cells, macrophages, and B cells, engulf foreign invaders or cellular debris. Within these APCs, antigens are processed into smaller fragments. These fragments are then loaded onto specialized molecules called Major Histocompatibility Complex (MHC) molecules. There are two main classes of MHC molecules: MHC class I and MHC class II.

MHC class I molecules present antigens derived from intracellular pathogens or abnormal self-proteins, such as those found in cancer cells, to cytotoxic T lymphocytes (CTLs), also known as CD8+ T cells. MHC class II molecules, on the other hand, present antigens derived from extracellular pathogens that have been phagocytosed by the APC, to helper T lymphocytes (Th cells), also known as CD4+ T cells.

The T cell receptor (TCR) on the surface of T cells recognizes the specific antigen-MHC complex presented by the APC. This interaction is a key step in T cell activation, leading to the proliferation and differentiation of T cells into effector cells that can eliminate the threat or regulatory cells that help control the immune response. Without effective antigen presentation, T cells would not be able to recognize and respond to foreign antigens, leaving the body vulnerable to infections and diseases.