Antigenwahl

Antigenwahl, also known as antigen selection or antigen presentation, refers to the process by which the immune system identifies and responds to foreign substances, known as antigens, that enter the body. This process is fundamental to adaptive immunity, where the body’s defense mechanisms recognize and neutralize pathogens such as bacteria, viruses, and other harmful agents.

During antigen selection, immune cells, particularly B cells and T cells, play crucial roles. B cells produce antibodies that bind specifically to antigens, while T cells, especially cytotoxic T cells and helper T cells, recognize antigens presented by other immune cells. This recognition is highly specific and relies on the major histocompatibility complex (MHC) molecules, which display fragments of antigens on the surface of antigen-presenting cells (APCs) like dendritic cells, macrophages, and B cells.

The selection process begins when APCs capture antigens from pathogens and break them down into smaller peptides. These peptides are then loaded onto MHC molecules and displayed on the cell surface. Helper T cells, equipped with T cell receptors (TCRs), scan these MHC-antigen complexes. If a TCR recognizes the antigen with sufficient affinity, the T cell becomes activated, triggering a cascade of immune responses, including the production of cytokines that further stimulate B cells and other immune cells.

In the case of B cells, antigen recognition occurs when antibodies on their surface bind directly to free-floating antigens. This interaction leads to B cell activation, proliferation, and differentiation into plasma cells, which secrete large quantities of antibodies tailored to neutralize the specific antigen. The immune system’s ability to distinguish between self and non-self antigens is critical to prevent autoimmune reactions, where the body mistakenly attacks its own tissues.

Antigen selection is a dynamic and adaptive process, ensuring that the immune response is targeted and efficient. It underpins vaccination strategies, where weakened or inactivated pathogens are introduced to stimulate antigen selection and generate long-lasting immunity. Errors or dysfunctions in this process can lead to immune deficiencies, autoimmune diseases, or inadequate responses to infections.