vastaaineita

Vasta-aineita (antibodies) are Y-shaped glycoproteins of the adaptive immune system produced mainly by plasma cells derived from B lymphocytes. They recognize specific antigens—foreign molecules such as proteins on pathogens or toxins—and bind them with high specificity. Each antibody consists of two identical heavy chains and two identical light chains, forming Fab (antigen-binding) fragments and an Fc (crystallizable) fragment. The variable regions confer antigen specificity, while the constant regions define the immunoglobulin class (IgG, IgM, IgA, IgD, IgE). Immunoglobulin diversity arises through gene rearrangement (V(D)J recombination), followed by somatic hypermutation and class-switch recombination during immune responses.

Antibodies participate in multiple effector mechanisms: neutralization of toxins and viruses, agglutination and precipitation of antigens, opsonization to enhance phagocytosis, activation of the classical complement pathway, and antibody-dependent cellular cytotoxicity. They also form the basis of immunological memory, enabling rapid and robust responses upon re-exposure to the same antigen.

Clinically, antibodies are used in diagnostics (serology tests such as ELISA and Western blot) and therapeutics (monoclonal antibodies for cancer, autoimmune diseases, and infections). Vaccines aim to elicit protective antibody responses. The structure and function of antibodies were elucidated in the 20th century, with Gerald Edelman and Rodney Porter awarded the Nobel Prize in Physiology or Medicine in 1972 for discoveries concerning the structure of antibodies.