β 2 - M i c r o g l o b u l i n . β 2 - M i c r o g l o b u l i n ( B 2 M ) i s t h e l i g h t c h a i n c o m p o n e n t o f t h e m a j histocompatibility complex (HLA). This protein is found on the surface of most nucleated cells and is present in high concentrations on lymphocytes. Because of its small size (MW, 11,800), B2M is filtered by the renal glomerulus but most (>99%) is reabsorbed and catabolized in the proximal tubules. o r
Complement. Complement is a collective term for several proteins that participate in the immune reaction and serve as a ink to the inflammatory response. These proteins circulate in the blood as nonfunctional precursors. In the classic pathway, activation of these proteins begins when the first complement factor, Clq, binds to an antigen-antibody complex. The binding occurs at the Fc, or constant, part of the IgG or IM molecule. Each complement protein (C2-C9) is then activated sequentially and can bind to the membrane of the cell to which the antigen-antibody complex is bound. The final result is lysis of the cell. In addition, complement is able to enlist the participation of other humoral and cellular effector systems in the process of inflammation. An alternate pathway (properdin pathway) for complement activation exists in which the early components are bypassed and the process begins with C3. This pathway is triggered by different substances (does not require the presence of an antibody), however, the lytic attack on membranes is the same (sequence C5-C9).
Fibrinogen. Fibrinogen is one of the largest proteins in blood plasma. It is synthesized in the liver, and it is classified as a glycoprotein because it has considerable carbohydrate content. On plasma electrophoresis, fi- brinogen is seen as a distinct band between the β- and γ-globulins. The function of fibrinogen is to form a fibrin clot when activated by thrombin; therefore, fibrinogen is virtually all removed in the clotting process and is not seen in serum.
C-Reactive Protein. C-Reactive protein (CRP) is synthesized in the liver and appears in the blood of patients with diverse inflammatory diseases. CRP was so named