Staphylococcus aureus-derived chemoattractant activity for human monocytes.

Products of bacteria are potent chemoattractants for mammalian leukocytes. Several reports suggest that these attractants are small peptides. We compared the properties of culture fluids of Staphylococcus aureus with fMet-Leu-Phe, considered a prototype of bacterial attractant. Chemotactic activity for human monocytes of Staph. aureus culture filtrates was determined in multiwell chemotaxis chambers. At optimal concentrations, the filtrate attracted almost twice as many monocytes as fMet-Leu-Phe (53 +/- 5% of input number compared with 30 +/- 3%, in a series of ten experiments). Gel-filtration characteristics and susceptibility to proteolytic digestion suggested that chemotactic activity was due to peptides with a molecular size range of 500-2,000 daltons. Reverse-phase high-pressure liquid chromatography (HPLC) of unfractionated filtrate revealed nine peaks of chemotactic activity, most of which was in five of the peaks. One peak accounted for 40% of total activity. Individual peaks, like the unfractionated material, were capable of attracting about twice as many monocytes as the optimal concentration of fMet-Leu-Phe. Quantitative bioassay of the HPLC peaks showed that only 5% of the total Staph. aureus chemotactic activity eluted in the position of fMet-Leu-Phe. This is in contrast to the report that fMet-Leu-Phe accounted for 70% of neutrophil lysosomal enzyme-releasing activity of Escherichia coli culture fluid. In summary, chemotactic activity for monocytes of Staph. aureus culture fluid is due to peptides other than fMet-Leu-Phe; these peptides recruit a higher percentage of monocytes than fMet-Leu-Phe.