The humoral immune program is usually a properly developed fortress that defends its host against foreign invasion. The sentinels of this fortress are macrophages that continually roam the bloodstream of their host. When challenged by infection or immunization, macrophages respond by engulfing invaders marked with foreign molecules (antigens). This event, mediated by helper T cells, sets forth a complicated chain of responses that results in the stimulation of B-cells. These B-cells, in turn, make proteins named antibodies which bind for the foreign invader. The binding event involving antibody and antigen marks the foreign invader for destruction by way of phagocytosis or activation on the complement system.
Five unique classes of antibodies (or immunoglobulins) exist: IgA, IgD, IgE, IgG, IgM. They differ not just in their physiological roles but in addition in their structures. From a structural point of view, IgG antibodies are a certain class of immunoglobulins that have been extensively studied, perhaps due to the dominant function they play inside a mature immune response. A considerable quantity of what we know regarding the structure of antibodies comes from X-ray crystallographic and immunoglobulin gene sequencing studies. The structure of an IgG antibody is shown schematically in Figure 1. IgG antibodies are Y-shaped proteins composed of two heavy chains and two light chains that are joined by disulfide linkages. The IgG molecule is usually broken down into two regions, the Fc and Fab. The Fc region, so known as since it is definitely the fragment of the IgG molecule that most readily crystallizes, is involved in effecting the physiological roles the antibody must play. Two identical Fab fragment are present in the ends on the "Y" in every IgG structure. The Fab area is named as such because it would be the IgG fragment that contains the antibody binding site. The Fab region consists of a region of highly conserved amino acids as well as a area of very variable amino acids (Fv). These variable sequences are confined to six protein loops (or complementarity figuring out regions) that cluster collectively in the finish of the Fab fragments to form a continuous hypervariable surface. It's this area that is responsible for the binding of foreign antigens.
Related Tags : blood antibody , monoclonal antibodies production