Antibody molecules are roughly Y-shaped glycoproteins with a molecular weight of approximately 150 kDa. A typical IgG antibody has two copies of each of two polypeptide chains: the light chain (25 kDa) and the heavy chain (50 kDa). The disulfide bonds link two heavy chains to each other and each heavy chain to a light chain. These chains pair in such a way as to create three structural domains, two antigen-binding fragments (Fabs) and one crystallizable fragment (Fc), that are linked by a flexible “hinge” region. The antibody can be readily cleaved into Fab and Fc fragments by proteases. CH2 and CH3 comprise the Fc fragment, which can bind to cell surface receptors present on immune cell populations. The Fab fragment is a mixed light-heavy chain dimer of variable light (VL)-constant light (CL) paired with variable heavy (VH)-constant heavy 1 (CH1) segments. There are five types of Ig H chain (α, δ, ε, γ, and μ) and two types of Ig L chain (λ and κ) in mammals.
Fig 1. Structure of a monoclonal antibody. (Loureiro, 2015)
In any given antibody, the two H chains and the two L chains are identical, giving an antibody molecule two identical antigen-binding sites. This endows the antibody with the ability to bind to two identical antigens on a surface simultaneously, thereby increasing the strength of the interaction. Fabs contain antigen-binding sites. The Fc fragment is the part of the antibody molecule that does not interact with antigen, but rather interacts with effector molecules and cells, and it differs between H chain isotypes.
In addition to the dominant full-length monoclonal antibodies, antibody engineering technologies have progressed in recent years to produce highly optimized therapies. Several engineered antibodies are as follows.
Fig 2. Various genetically engineered antibody fragments. (Jain, 2007)
Creative Biolabs has built up a world-class ecosystem of expertise and capabilities to provide you a personalized solution to meet all your demands. We can provide various ViroAntibody products including a wide range of primary antibodies, secondary antibodies, isotype controls. If you are interested in our products, please feel free to contact us for more information.