Anticossos

Anticossos, commonly known as antibodies in English, are large glycoproteins produced mainly by plasma cells as part of the adaptive immune system. They recognize and bind specific antigens—molecules or parts of pathogens such as proteins on bacteria or viruses—thereby neutralizing them or marking them for attack by other immune components.

Structure: Anticossos are built from four polypeptide chains: two identical heavy chains and two identical light chains, linked by disulfide bonds. Each chain has constant and variable regions, with the variable regions forming the two antigen-binding sites at the tips of the Y-shaped molecule. The Fc region, composed of the constant parts, mediates interactions with immune cells and the complement system and can be glycosylated.

Classes: In humans there are five major isotypes—IgA, IgD, IgE, IgG, and IgM—each with distinct distributions and functions. Antibodies are produced by B cells and diversified through V(D)J recombination and somatic hypermutation, enabling a broad ability to recognize many antigens.

Functions and roles: Primary functions include neutralization of pathogens and toxins, opsonization to enhance phagocytosis, activation of the classical complement pathway, and antibody-dependent cellular cytotoxicity. Some antibodies provide mucosal protection (IgA) while others can cross the placenta (IgG). Antibodies also participate in immune memory following exposure to antigens.

Applications and relevance: Antibodies are central to diagnostics (serology tests), research, and therapy. Monoclonal antibodies are engineered for targeted treatments in cancer, autoimmune diseases, and infectious diseases. Vaccines aim to provoke protective antibody responses to prevent infection.