EFFECT OF EX-VIVO STORAGE ON HUMAN PERIPHERAL-BLOOD NEUTROPHIL EXPRESSION OF CD11B AND THE STABILIZING EFFECTS OF CYTO-CHEX(TM)

CD11b is the alpha sub-unit of the CD11b/CD18 heterodimeric complex th at has a key role in neutrophil-endothelial cell interactions and earl y events in inflammatory responses. Accurate assessment of CD11b expre ssion by neutrophils can be problematic since the procedures that isol ate cells from whole blood can increase antigen expression. This study used whole blood flow cytometry to monitor neutrophil CD11b expressio n following 0, 1, 2, 3 and 4 h of ex vivo incubation at room temperatu re and examined the effects of storage at 4 degrees C and the cell sta bilization solution, Cyto-Chex(TM), on antigen expression. Cyto-Chex(T M)-treated samples were also re-analyzed after 7 days storage at 4 deg rees C. Neutrophil CD11b expression was high (> 90%) in five of the se ven samples studied and incubation at room temperature induced a progr essive upregulation which was significant after 2, 3, and 3 h (p < 0.0 5). Storage at 4 degrees C tempered this effect, although an increased expression (from baseline) was still observed after 4 h (p < 0.05). C yto-Chex(TM) had no effect on the light scatter characteristics of tre ated cells and prevented CD11b upregulation in samples stored at room temperature. Furthermore, expression in Cyto-Chex(TM)-treated samples after 7 days was not significantly different from that observed in bas eline (time 0) samples. In two samples demonstrating low neutrophil CD 11b expression, a temperature-independent increase in the proportion o f CD11b(+) cells was observed over time. However, this increase was at tenuated by treatment with Cyto-Chex(TM). These findings indicate that sample storage significantly affects CD11b expression and caution sho uld be exercised when interpreting data. Given that Cyto-Chex(TM) had no effect on the light scatter properties of cells and prevents antige n upregulation, this reagent may be useful for studies involving analy sis of neutrophil activation antigen expression. (C) 1998 Elsevier Sci ence B.V. All rights reserved.