Learn more about the advantages of F(ab) and F(ab')2 fragments. Fc fragments are often used as Fc receptor blocking agents in immunohistochemical staining. Often, because of their smaller size and lack of cross-linking (due to the Fc region's loss), F(ab) fragments are radiolabeled in functional studies. Fragmenting IgG antibodies is sometimes useful because F(ab) fragments (1) will not precipitate the antigen, and (2) will not be bound by immune cells in live studies because of the lack of an Fc region. Also, dye and enzymes can be covalently linked to antibodies on the Fc portion of the antibody for experimental visualization.Īntibody fragments have distinct advantages in specific immunochemical techniques. The Fc fragment provides a binding site for endogenous Fc receptors on the surface of lymphocytes and secondary antibodies. The F(ab) regions contain the variable domain that binds to cognate (specific) antigens. The Y-shape of an antibody can be cleaved into three fragments by the proteolytic enzyme pepsin: two F(ab) regions and an Fc region. V H – heavy chain variable domain, V L- light chain variable domain, C H – heavy chain constant domain, C L – light chain constant domain. The base of the antibody includes constant domains (C). Antigen binding occurs at the variable domain (V), consisting of immunoglobulin heavy (H) and light chains (L). This region is essential for the function of the antibody during an immune response.įigure 1. Antibody structure. The Y-shaped antibody is joined in the middle by a flexible hinge region. The antibody base consists of constant domains (C) and forms the fragment crystallizable region (Fc). This region binds tightly to a specific part of an antigen called an epitope. The top of the Y shape contains the variable region (V), also known as the fragment antigen-binding (F(ab)) region. Each Y unit contains two identical copies of a heavy chain (H) and two identical copies of a light chain (L) heavy and light chains differ in their sequence and length. Antibodies specifically bind unique pathogen molecules called antigens.Īntibodies exist as one or more copies of a Y-shaped unit composed of four polypeptide chains (Fig. Guide to the structural components that make up an antibody - heavy chains, light chains, F(ab)/Fc regions - and antibody isotypes.Īntibodies, also known as immunoglobulins (Ig), are large, Y-shaped glycoproteins produced by B-cells as a primary immune defense.
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