FITC Mouse Anti-Human IgG Antibody (S-4825)

Human immunoglobulin G (IgG) is the most abundant and important antibody type in serum, accounting for approximately 75-80% of all immunoglobulins. It is widely distributed in blood, lymph, and tissues, serving as a core effector molecule of the adaptive immune response. IgG is composed of four polypeptide chains—two identical heavy chains (γ chains) and two identical light chains (κ or λ chains)—connected by disulfide bonds to form a characteristic Y-shaped structure. It can be further divided into four subclasses: IgG1, IgG2, IgG3, and IgG4, each differing in hinge region flexibility, number of disulfide bonds, and effector functions. The primary functions of IgG include: recognizing and binding with high affinity to antigens from bacteria, viruses, or toxins via the variable region (Fab fragment) to form immune complexes; binding to Fc receptors on the surface of phagocytes and natural killer cells via the constant region (Fc fragment) to mediate opsonization and antibody-dependent cell-mediated cytotoxicity (ADCC). In addition, IgG is the only antibody subclass that can cross the placental barrier, providing passive immune protection to the fetus, and is involved in activating the classical complement pathway (particularly IgG1 and IgG3). In clinical and research settings, detection of specific IgG antibodies is commonly used to diagnose past infections or evaluate immune responses following vaccination, while recombinant human IgG monoclonal antibodies have been widely developed for the treatment of autoimmune diseases, malignancies, and infectious diseases.