**2.2.1 CD11b**

There was a similar expression of CD11b on monocytes and neutrophils in patients on highflux hemodialysis/hemodiafiltration and healthy subjects, both in the peripheral circulation and at the three sites of interstitial inflammation. *In vitro* activation with fMLP induced a significant increase in the expression of CD11b on monocytes and neutrophils in the peripheral circulation and at the sites of interstitial inflammation, both in patients on highflux hemodialysis/hemodiafiltration and healthy subjects.

The preserved capacity of both monocytes and neutrophils to express CD11b at the sites of interstitial inflammation in patients on high-flux hemodialysis/hemodiafiltration, as shown by our findings, may have important biological consequences in terms of an adequate performance of leukocyte functions in which the CD11b molecule plays a key role (Thylen et al. 1997; Moshfegh et al. 2002). Extravasated neutrophils and monocytes from patients on high-flux hemodialysis/hemodiafiltration showed a maintained response to fMLP as a second inflammatory stimulus after extravasation.

The mechanism behind this preserved leukocyte function in patients on high-flux biocompatible hemodialysis/hemodiafiltration could be the removal of small and middlesized leukocyte inhibitory molecules by high-flux hemodialysis/hemodiafiltration (Vanholder et al. 1994a), but membrane compatibility could also play an important role.
