Flow cytometric study of in vitro neutrophil activation by biomaterials

Neutrophil activation for adherent and nonadherent cells, as measured by fl ow cytometry, was not strongly dependent on material surface chemistry. We had hypothesized that material-induced neutrophil activation was an importa nt parameter associated with material failure. All materials tested [cellop hane, an acrylonitrile copolymer (AN69), Pellethane(TM) nylon, polyethylene terephthalate, low density polyethylene, and polydimethylsiloxane] activat ed isolated human neutrophils, which were resuspended in plasma or serum, t o similar extents based on L-selectin shedding, CD11b upregulation, and sti mulation of the oxidative burst after 30-min exposure. Inhibition of comple ment activation by sCR1 unexpectedly had Little effect if any on nonadheren t neutrophils. However, neutrophil adhesion, but not the level of activatio n of the adherent cells, was strongly dependent on complement activation. P retreatment with albumin did not inhibit adhesion or reduce neutrophil acti vation, but plasma pretreatment resulted in increased activation for nonadh erent and adherent cells. More adhesion and a higher level of activation of adherent cells was observed following pretreatment with fibrinogen, a liga nd of CD11b. Taken together these results suggest that upon contact with a material, neutrophil activation may occur though mechanisms that are not me diated by complement. For example, the presence of plasma proteins such as fibrinogen at the interface may trigger activation and the release of other activating agents. Although the material differences are small, the extent of activation may be significant and warrant further study of the mechanis m and consequences of that activation. (C) 1999 John Wiley & Sons, Inc.