Macrophage accumulation in primary and transplanted tumors growing in C5-deficient B10.D2/oSn mice.

The hypothesis was tested that the fifth component of complement (C5) was required for the accumulation of macrophages at the site of tumor growth. This was based on the assumption that the cleavage product of C5, C5a, attracts peripheral blood monocytes along a chemotactic gradient. Methylcholanthrene-induced primary and transplanted tumors were grown in the genetically C5-deficient B10.D2/oSn strain and the C5-positive B10.D2/oSn strain and their macrophage content assessed after enzymic disaggregation of the tumors. The overall data indicated that there were no significant differences in the two strains since macrophages accumulated in the tumors irrespective of the presence of C5 or its cleavage product C5a.