Antigen Processing

Antigen Processing is a fundamental process in the immune system that plays a crucial role in vaccine development. It involves the degradation of foreign antigens, such as proteins or peptides derived from pathogens, into smaller fragments that can be presented to immune cells called T lymphocytes. The process of antigen processing begins when antigen-presenting cells, such as dendritic cells, macrophages, and B cells, engulf foreign invaders through a process called phagocytosis. Once inside the cell, the antigens are broken down into peptides by specialized enzymes called proteases.

These peptide fragments are then transported to the cell's surface, where they are displayed on molecules called major histocompatibility complex (MHC) molecules. MHC molecules act as molecular flags, presenting the antigen fragments to T lymphocytes, which play a central role in coordinating the immune response. There are two main types of MHC molecules involved in antigen presentation: MHC class I and MHC class II. MHC class I molecules present peptides derived from intracellular pathogens, such as viruses and intracellular bacteria, to cytotoxic T lymphocytes (CD8+ T cells). This process allows the immune system to detect and eliminate infected cells.

On the other hand, MHC class II molecules present peptides derived from extracellular pathogens, such as bacteria and parasites, to helper T lymphocytes (CD4+ T cells). Helper T cells play a crucial role in activating other immune cells and coordinating the adaptive immune response. In the context of vaccine development, understanding antigen processing is essential for designing vaccines that can effectively stimulate T cell responses. Vaccines may contain whole pathogens, inactivated pathogens, or specific antigens derived from pathogens. By targeting antigens that undergo efficient processing and presentation, vaccines can elicit strong and durable immune responses.