AntikörperIsotyp

AntikörperIsotyp, also known as antibody isotype or immunoglobulin class, refers to the different classes of antibodies produced by the immune system. These classes are distinguished by variations in their heavy chains, specifically the constant region. The five major isotypes in mammals are IgG, IgM, IgA, IgD, and IgE. Each isotype has a distinct structure, effector function, and distribution within the body, allowing them to mediate different aspects of the immune response.

IgG is the most abundant isotype in serum and is crucial for long-term immunity, neutralization of toxins, and complement activation. It is the only isotype that can cross the placenta, providing passive immunity to the fetus. IgM is the first antibody produced during a primary immune response and is a potent activator of the complement system. It exists as a monomer in serum and as a pentamer on the surface of B cells. IgA is the predominant isotype in mucosal secretions like saliva, tears, and breast milk, playing a vital role in protecting mucosal surfaces from pathogens. IgD is primarily found on the surface of mature naive B cells and is thought to be involved in B cell activation. IgE is present at very low concentrations in serum but is critical in defense against parasitic infections and is responsible for allergic reactions. The specific isotype produced is determined by the B cell's developmental stage and the signals it receives from its environment. This diversity in isotypes allows the immune system to mount tailored responses to a wide range of threats.