antibodiesproteins

Antibodies, also called immunoglobulins, are large, Y-shaped glycoproteins produced mainly by plasma cells that recognize and bind specific antigens. They are a major component of the adaptive immune response. Each antibody has two identical heavy chains and two identical light chains, linked by disulfide bonds. The variable regions at the tips of the arms form the antigen-binding sites; the constant region determines the effector function through interactions with Fc receptors and complement proteins. Antibodies are produced by B lymphocytes after V(D)J recombination and somatic hypermutation, enabling vast diversity. They can exist as membrane-bound B cell receptors or as soluble secreted immunoglobulins. They belong to a larger family of proteins called immunoglobulins; in humans there are five major classes (isotypes): IgA, IgD, IgE, IgG, and IgM, each with distinct roles and distributions.

Functions include neutralization of pathogens and toxins, opsonization to promote phagocytosis, activation of the complement cascade, antibody-dependent cellular cytotoxicity, and agglutination or precipitation of antigens. Antibody responses can be polyclonal, produced by many B cells, or monoclonal, derived from a single B cell lineage and widely used in research and medicine. Monoclonal antibodies can be engineered for therapeutic use as chimeric, humanized, or fully human antibodies. Production methodologies include hybridoma technology, phage display, and recombinant DNA techniques. Antibodies are used in diagnostics (ELISA, western blot) and therapy for infections, cancers, autoimmune diseases, and inflammatory conditions.