Monoclonal antibody I8/1 recognizes human complement factor D. Factor D is a 27 kDa serine protease that replaces the complement pathway and is synthesized as a precursor single-chain molecule. The alternative complement pathway represents an alternative complement pathway for an important body fluid component for natural defenses Participation is related to the pathogenesis of a variety of human diseases.
Factor D is unique among serine proteases because it neither requires enzyme cleavage to express proteolytic activity nor activation of serine protease inhibitors to control it. Factor D is highly specific and cleaves factor B that binds to C3b, thereby generating C3bBb enzyme. Factor D is the rate-limiting C3 convertase of the alternative pathway. It has the lowest plasma concentration and lowest molecular weight of all complement components. The normal values ​​of human EDTA plasma and urine are 1.05 (±0.27) and 0.62 (±0.33) µg/ml, respectively. In normal human subjects, factor D is rapidly eliminated by the kidneys. Compared with the control group, the levels of factor D in the plasma and urine of patients with renal failure increased. Plasma levels increase within seven days after successful kidney transplantation and return to normal levels to prevent excessive stimulation of the complement pathway.
Human lipase is a protein expressed at high levels in adipose tissue, which is the same as factor D, and also shows the same enzymatic activity as factor D. This indicates that the role of factor D in adipose tissue is different from its role as a complement protein.