PURIFICATION AND CHARACTERIZATION OF A PHAGOCYTOSIS INDUCING FACTOR -ROLE IN CELL-SUBSTRATUM ADHERENCE

The presence of two different signaling molecules is essential to indu ce opsonin-independent phagocytosis of particulate activators of the h uman alternative complement pathway by human monocytes. In addition to the involvement of a low M-r peptide cytokine or phagocytosis inducin g factor (PIF), we have now established that the participation of bact erial lipopolysaccharide is also required. PIF has been demonstrated t o be present in human cell lines of different origins, e.g., WISH cell s, Raji cells, U937 cells, HL-60 cells and M21 cells, PIF has been pur ified to apparent homogeneity from the U937 cell line by anion-exchang e chromatography on DEAE-Sephacel followed by gel filtration chromatog raphy on Sephadex G-50, On the basis of Tricine-sodium dodecyl sulfate -polyacrylamide gel electrophoresis, the apparent molecular mass has b een estimated to be approximately 1,600 Da, PIF also plays an importan t role in the regulation of cell-substratum adherence. (C) 1998 Academ ic Press.