Expression of properdin in human monocytes

Properdin is the only known positive regulator of the alternative pathway of complement activation. Northern blot analysis of cell lines derived from fibroblasts, B-cells, hepatoma cells, and cells of the monocyte-macrophage lineage revealed properdin expression only in the myelomonocytic cell line HL-60, in the monoblastic cell line U-937 and in the monocytic line Mono Mac 6. Culture of Mono Mac 6 cells for 24 h with phorbol 12-myristate 13-acetate, bacterial lipopolysaccharide and the cytokines interleukin-1 beta and tumour necrosis factor-alpha enhanced mRNA abundance, with the strongest effect (tenfold) being observed with the lipopolysaccharide. In contrast, recombinant interferon-gamm…