Fifth component of complement (C5)-derived high-molecular-weight macrophage chemotactic factor in normal guinea pig serum.

Normal guinea pig serum contain a chemotactic factor(s) for macrophages. As the chemotactic activity in the serum was absorbed by an anti-C5 antibody affinity column but not by the anti-C3 or anti-macrophage chemotactic factor from skin-1 (MCFS-1) affinity column, the major chemotactic factor in the serum was postulated to be C5-derived. This chemotactic factor, which was a heat-labile molecule with an apparent molecular weight of 150,000 (by gel filtration) and lacked vascular permeability activity, was distinct from the C5a-like anaphylatoxins. Using a combination of a Boyden chamber assay and a morphological polarization assay for the macrophage chemotaxis, it was revealed that this chemotactic factor was latent in plasma and could be activated by incubation for 30 min at 37 degrees C in the presence of a sufficient amount of Ca ion (5 mM) concomitant or not concomitant with the clot formation of the plasma. Precursor of MCFS-1 in plasma was not activated during coagulation.