Antikeha

Antikeha refers to an antibody or immunoglobulin, a large, Y-shaped protein produced mainly by plasma cells that recognize and bind to specific antigens. Antibodies are a key component of the adaptive immune system. They are produced by B lymphocytes following exposure to antigens and can persist as memory antibodies.

Structure and diversity: An antibody is composed of two identical heavy chains and two identical light chains linked by disulfide bonds. Each chain has constant and variable regions; the variable regions of the two arms form the antigen-binding sites, enabling high specificity. The Fc region interacts with other parts of the immune system, mediating effector functions.

Diversity and maturation: Antibody diversity arises from V(D)J recombination during lymphocyte development, followed by somatic hypermutation and class switch recombination that change isotype and effector function without changing antigen specificity. Isotypes include IgA, IgD, IgE, IgG, and IgM in humans, each with distinct roles.

Functions: Neutralization of pathogens, opsonization to promote phagocytosis, activation of the complement system, antibody-dependent cellular cytotoxicity, and recruitment of other immune cells. Antibodies can be produced naturally in response to infection or vaccination or generated as therapeutic monoclonal antibodies.

Clinical relevance: Serology detects antibodies to determine exposure or immunity. Therapeutic antibodies are used to treat cancers, autoimmune diseases, and infectious diseases. Autoantibodies can indicate autoimmune disorders, while antigenic variation can limit antibody effectiveness.

Note: In Estonian, antikeha is the term for an antibody; plural antikehad. The concept is broadly parallel to immunoglobulins across vertebrates.