Mótefnisrænt

Mótefnisrænt is the antibody-mediated portion of the adaptive immune system. It is driven primarily by B lymphocytes, which upon activation differentiate into plasma cells that secrete antibodies (immunoglobulins). These antibodies circulate in blood and extracellular fluids and recognize specific antigens, often pathogens outside host cells, as well as soluble toxins.

Key components of mótefnisrænt include B cells, plasma cells, memory B cells, and the various classes of antibodies (IgG, IgM, IgA, IgE, and IgD). Activation typically begins when B cells encounter an antigen and receive help from CD4+ T helper cells, leading to clonal expansion and differentiation. Memory B cells persist after an infection or vaccination, enabling a faster secondary response.

The main functions of mótefnisrænt are neutralization of pathogens and toxins, opsonization to promote phagocytosis, and activation of the complement system via the classical pathway. Antibodies can also mediate antibody-dependent cellular cytotoxicity (ADCC), where effector cells such as natural killer cells destroy antibody-coated targets. These actions are especially important against extracellular bacteria and viruses before they enter host cells or during phases when pathogens are exposed to circulating antibodies.

Mótefnisrænt is distinct from cell-mediated immunity, which is principally driven by T lymphocytes and targets infected cells rather than extracellular entities. In clinical contexts, serological tests measure antibody responses to assess exposure or immunity, and vaccines aim to elicit durable mótefnisrænt memory.