Antikropp

Antikropp, or antibody, is a large Y-shaped protein produced mainly by plasma cells as part of the adaptive immune system. Antikroppar recognize specific molecular features called antigens and can neutralize pathogens or mark them for attack by other parts of the immune system.

Antikroppar are immunoglobulins composed of two identical heavy chains and two light chains, forming variable regions that bind antigens and a constant Fc region that interacts with immune cells. There are five major isotypes in humans: IgM, IgG, IgA, IgE, and IgD, each with distinct roles and tissue distribution.

Most antikroppar originate from B cells. Upon antigen exposure and help from T cells, B cells differentiate into plasma cells that secrete large amounts of antibodies. Through somatic hypermutation and class switching in germinal centers, antibodies increase affinity and change isotype.

Functions include neutralization of toxins or viruses, opsonization to enhance phagocytosis, activation of the classical complement pathway, and antibody-dependent cellular cytotoxicity. Antikroppar can be produced in response to pathogens or vaccines, and memory B cells provide rapid responses upon re-exposure.

In medicine, serological tests detect antikroppar to diagnose infections or autoimmune diseases. Autoantibodies are antibodies directed against self-antigens, seen in conditions such as lupus and rheumatoid arthritis. Monoclonal antibodies are laboratory-generated antikroppar used therapeutically in cancer, autoimmune disease, and infectious disease. Examples include anti-dsDNA antibodies in systemic lupus erythematosus and anti-CCP antibodies in rheumatoid arthritis.