INHIBITION OF CHEMOTAXIS OF NEUTROPHIL LEUKOCYTES TO INTERLEUKIN-8 BY ENDOTOXINS OF VARIOUS BACTERIA

The effects of endotoxins from various bacteria (Escherichia coli, Klebsiella pneumoniae, Vibrio cholerae, Shigella flexneri, Salmonella typhosa, and Pseudomonas aeruginosa) on chemotaxis of neutrophil leukocytes to formyl peptide and interleukin-8 were tested in an improved chemotaxis assay involving a "sparse-pore" polycarbonate (Nucleopore) membrane in a Boyden-type chamber. The possible chemotactic activity of the endotoxins themselves were tested by the same technique. In addition, the effects of these substances on random motility of neutrophils were tested with a corresponding assay involving similar chambers fitted with membranes of standard pore density. Possible activation of the complement system of serum by each endotoxin was tested with sheep erythrocyte assays and the maximum endotoxin concentration (100-mu-g/ml) used in the chemotaxis and motility assays. All endotoxins inhibited chemotaxis of neutrophils to interleukin-8. No endotoxin affected chemotaxis to formyl peptide or was itself chemotactic for neutrophils. Endotoxin of S. flexneri inhibited random motility of neutrophils, while the others had no such effect. Endotoxins of K. pneumoniae and of P. aeruginosa produced moderate and marked inhibition, respectively, of total complement, as measured by hemolysis of sheep erythrocytes, without affecting the levels of C3c and C4 in these assays. Endotoxins of the other bacteria had no demonstrable effect in any of these assays of complement activation. These results suggest that chemotaxis to interleukin-8 may be mediated by cellular mechanisms different from those involved in chemotaxis to formyl peptide. Furthermore, the presence of these endotoxins could be significant for the suppression of neutrophil accumulation in inflammatory lesions mediated by interleukin-8.