Monocyte-chemotactic activity of defensins from human neutrophils

Abstract

We investigated the monocyte-chemotactic activity of fractionated extracts of human neutrophil granules. Monocyte-chemotactic activity was found predominantly in the defensin-containing fraction of the neutrophil granules. Purified preparations of each of the three defensins (HNP-1, HNP-2, HNP-3) were then tested. HNP-1 demonstrated significant chemotactic activity for monocytes: Peak activity was seen at HNP-1 concentrations of 5 x 10-9 M and was 49 ± 20% (mean ± SE, n = 9) of that elicited by 10-8 M FMLP. HNP-2 (peak activity at 5 x 10-9 M) was somewhat less active, yielding 19 ± 10% (n = 11). HNP-3 failed to demonstrate chemotactic activity. Checkerboard analysis of monocyte response to HNP-1 and HNP-2 confirmed that their activity was chemotactic rather than chemokinetic. Neutrophils demonstrated a low level of response to defensins but this reaction was primarily chemokinetic. Defensins may play a role in the recruitment of monocytes by neutrophils into inflammatory sites.