Reacts with: Guinea Pig, Cat, Mouse, Rat, Dog, Horse.

The complement Factor H protein is secreted into the bloodstream and acts in the regulation of complement activation. Mutations leading to changes in this protein have been linked with HUS (hemolytic-uremic syndrome) and chronic hypocomplementemic nephropathy.Factor H is mainly synthesised in the liver but also in macrophages and endothelium.It is primarily aplasma glycoprotein but is also found in platelets and there is a membrane bound form on some leukocytes.Consisting of a single polypeptide, the major form of Factor H has a molecular weight of 155kDa.There are two truncated forms, a non-glycosylated 49 kDa form and a glycosylated 39-43 kDaform.Plasma concentrations are in the range 200-600mg/L for the 155 kDa form and 1-5mg/L for thetruncated forms.Factor H is a major regulatory protein of the complement system.By binding to C3b it either displacesor prevents the binding of Bb (activated Factor B).When bound to Factor H, C3b is susceptible tocleavage by Factor 1 to yield iC3b.Factor H is released or modified following this cleavage.The regulatory role of Factor H is essential because C3bBb is not only a C5 convertase but a C3 convertaseand so has a positive feedback effect, potentially consuming the entire C3 pool if unregulated.