Antigeenideantikehade

Antigeenideantikehade are antibodies against antigens produced by the immune system. In immunology, antibodies (immunoglobulins) are large, Y-shaped glycoproteins produced mainly by plasma cells derived from B lymphocytes. They recognize and bind to specific epitopes on antigens with high specificity.

They have a modular structure: two identical heavy chains and two identical light chains form antigen-binding sites (Fab) and a crystallizable fragment (Fc) that interacts with other components of the immune system. The antigen-binding regions are highly variable, allowing recognition of a vast array of antigens.

Antigen recognition triggers multiple effector pathways. Neutralization blocks pathogenic activity; opsonization promotes phagocytosis; the classical complement pathway can be activated; antibody-dependent cellular cytotoxicity (ADCC) involves effector cells. Antibody responses develop during humoral immunity, initiated when B cells encounter antigens and receive helper signals. Clonal expansion leads to plasma cells producing antibodies and memory B cells for faster responses on re-exposure. Class switching alters the heavy-chain isotype (e.g., IgM to IgG, IgA, or IgE) without changing antigen specificity.

There are monoclonal antibodies, derived from a single B cell clone, and polyclonal antibodies, a mixture from multiple B cell clones. Monoclonal antibodies are widely used in diagnostics and therapy, including cancer treatment and autoimmune disease management. Antigen-antibody interactions underpin many laboratory assays, such as ELISA and immunohistochemistry, and are integral to vaccine-induced protection and immune surveillance.