The effect of ex vivo refrigerated storage and cell preservation solution (Cyto-Chex II™) on CD11b expression and oxidative burst activity of dog neutrophils

The expression of CD11b and oxidative burst activity of dog neutrophils undergoing ex vivo refrigerated storage was studied using flow-cytometry. Additionally, the effect of a proprietary cell stabilization reagent (Cyto-Chex™) on the expression of CD11b and oxidative burst activity was studied. Expression of CD11b was very high (>90% positive) on dog neutrophils isolated from peripheral blood. Dog neutrophils showed a rapid and sustained increase in CD11b antigen density (P<0.01) during refrigerated storage, this increase was prevented by treatment with Cyto-Chex™ but was not completely blocked on the first day. There were no significant differences in mean antigen density between any days in the non-preserved group or between Days 1 to 4 in the Cyto-Chex™ treated group. The non-treated group showed significantly greater mean antigen density at all time points when compared to the preservative treated group (P<0.0001). Treatment with Cyto-Chex™ did not interfere with measurement of oxidative burst function on the first 2 days. Alterations of both resting oxidative activity and stimulated response were observed over time in both treated and untreated blood samples. Cyto-Chex™ treated samples showed a dramatic, significant decline in stimulated response after the third day of storage (P<0.001), while non-treated cells showed steadily increasing, but non-significant differences in stimulated response. Cyto-Chex™ was demonstrated to be a useful reagent for stabilization of dog neutrophil membrane antigens during storage, however this reagent is not recommended for preservation of cells for functional assays.