Stimulation of neutrophil phagocytosis of Aspergillus fumigatus conidia by interleukin-8 and N-formylmethionyl-leucylphenylalanine.

The effect of the chemoattractants, interleukin-8 (IL-8) and N-formylmethionyl-leucylphenylalanine (fmlp) on neutrophil phagocytosis of serum-opsonised Aspergillus fumigatus conidia were studied. Pre-exposure of neutrophil monolayers to IL-8 (10-100 ng ml-1) or fmlp (10(-6)M) for 20 min increased phagocytosis from 15% to 35%. Furthermore, there was a significant increase in the numbers of conidia ingested by active neutrophils. The chemoattractants did not enhance phagocytosis of conidia when added contemporaneously to neutrophil monolayers. The ability of each chemoattractant to act as a primer for the other was investigated. It was found that fmlp could prime for IL-8 and fmlp enhancement of phagocytosis, but IL-8 could not. An increase from 15% to 55% in phagocytosis was seen at a pre-exposure concentration of 10(-5) M fmlp followed by an incubation period of 30 min in the presence of 20 ng ml-1 IL-8. There was no significant increase in the average number of internalized conidia under these conditions. The response of human neutrophils to priming stimuli may have important implications in the pathogenesis of aspergillosis.