IDENTIFICATION OF HUMAN-COMPLEMENT FACTOR-H AS A CHEMOTACTIC PROTEIN FOR MONOCYTES

We used chromatographic separation to purify to homogeneity a monomeri c monocyte chemotactic protein of 150 kDa contained in mesothelioma pl eural effusions. It was identified by N-terminal amino acid sequencing and immunoblotting as complement factor H, an inhibitor of the altern ative complement pathway. Specific antibodies against factor H inhibit ed the monocyte chemotactic activity of the purified protein, which wa s most active at 10 nM. Factor H is a restrictive factor of alternativ e complement pathway activation. The new chemotactic function assigned to factor H in recruiting monocytes to the mesothelioma site might co ntribute to malignant cell phagocytosis via the iC3b/complement recept or type 3 pathway. These functions link the humoral and cellular immun e systems.