The Immunoglobulins Antibodies

The fundamental role of blood in the maintenance of homeostasis and the ease with which blood can be obtained have meant that the study of its constituents has been of central importance in the development of biochemistry and clinical biochemistry. The basic properties of a number of plasma proteins, including the immunoglobulins (antibodies), are described in this chapter. Changes in the amounts of various plasma proteins and immunoglobulins occur in many diseases and can be monitored by electrophoresis or other suitable procedures. As indicated in an earlier chapter, alterations of the activities of certain enzymes found in plasma are of diagnostic use in a number of pathologic conditions. 

Humoral immunity results from the interactions of antigen, macrophages, helper T-cells and B-cells the latter which produces the immunoglobulins antibodies. Cellular Immunity is a function of a number of cell types identified as macrophages, killer cells, and T-cells (l3miphocytes) of which there are functional subpopulations of lymphocytes. The evidence suggesting an effect on cellular Immunity by Se is supported by dinitrochlorobenzene (DNCB) hypersensitivity experiments, allograft rejection times, impaired microbicidal activity, insensitivity of lymphocytes to Se deprivation and carcinostatic activity. 

Va.ria.tions in Methods. The various immunochemical methods can differ in a number of ways. For example, the analytical reagent may be cmde antisemm, monoclonal antibodies, isolated immunoglobulin fractions, etc. The conditions under which the method is mn, detection of the antigen—antibody complex, and the techniques used to increase sensitivity or specificity of the reaction all maybe varied. 

IgG antibody molecules are composed of two light chains and two heavy chains joined together by disulfide bonds. Each light chain has one variable domain and one constant domain, while each heavy chain has one variable and three constant domains. All of the domains have a similar three-dimensional structure known as the immunoglobulin fold. The Fc stem of the molecule is formed by constant domains from each of the heavy chains, while two Fab arms are formed by constant and variable domains from both heavy and light chains. The hinge region between the stem and the arms is flexible and allows the arms to move relative to each other and to the stem. 

Another application shows the preparative purification and polishing of a therapeutic fusion protein with a humanized recombinant IgG protein. The fusion protein was expressed by the fermentation of baby hamster kidney cells. The filtered culture supernatant (155 liters) contained 2.2 g of IgG and 75.5 g of total protein. After the immunoglobulins were isolated by expanded bed adsorption and rebuffering, the IgG fraction was bound to Fractogel EMD SOj (M). This column achieved baseline separation of complete antibodies (fusion protein) from small amounts of antibodies lacking the fusion part. The resulting highly purified IgG fraction (110 ml) was diluted to 150 ml and... 

A Type III allergic reaction occurs when antibodies of the immunoglobulin G class (IgG) form immune complexes which are slowly eliminated and thus may elicit an inflammatory reaction by binding to the Fey receptors of leukocytes resulting in their activation. 

Secondary antibody and determination. A secondary antibody labeled with an enzyme is added which binds to the primary antibody that is bound to the coating antigen. If the primary antibody were produced in a rabbit, an appropriate secondary antibody would be goat anti-rabbit immunoglobulin G (IgG) conjugated with horseradish peroxidase (HRP) (or another enzyme label). Excess secondary antibody is washed away. An appropriate substrate solution is added that will produce a colored or fluorescent product after enzymatic conversion. The amount of enzyme product formed is directly proportional to the amount of first antibody bound to the coating antigen on the plate and is inversely proportional to the amount of analyte in the standards. 

The diagnosis of hepatitis A is made by detecting immunoglobulin antibody to the capsid proteins of the HAV. The presence of IgM anti-HAVin the serum indicates an acute infection. IgM appears approximately 3 weeks after exposure and becomes undetectable within 6 months. In contrast, IgG anti-HAV appears in the serum at approximately the same time IgM anti-HAV develops but indicates protection and lifelong immunity against hepatitis A.1... 

Cellulose can be activated by CDI and coupled with the amino groups of peptides or immunoglobulins in aqueous alkaline solution to give immobilized peptides or antibodies such as the immunoglobulin IgG [210] (see also Section 6.2) ... 

---