Leucocyte Activity in Volunteers in Response to Experimental Venous Hypertension

Abstract

Objective:

To investigate leucocyte activation in normal volunteers subjected to short-term venous hypertension by measuring the cell surface expression of the integrin CD11b and the selectin CD62L on neutrophils and monocytes before and after short-term venous hypertension. Plasma levels of L-selectin, which is shed by leucocytes upon activation, were also measured.

Design:

Prospective study, measuring white cell count, neutrophil and monocyte surface CD11b and L-selectin expression in whole blood using a fluorescent-labelled monoclonal antibody in a flow cytometer, and plasma L-selectin by a commercially available ELISA.

Setting:

The Middlesex Hospital Vascular Laboratory, a referral centre for the investigation of venous diseases.

Subjects:

Twenty-five normal volunteers without any history or clinical finding of venous disease.

Results:

There was a significant fall in the white cell: red cell ratio (p = 0.03, Wilcoxon) in response to venous hypertension, followed by a significant increase (p < 0.001, Wilcoxon) when the venous hypertension was reversed. Neutrophil and monocyte CD11b levels fell significantly (p < 0.001 and p < 0.001, Wilcoxon) in response to venous hypertension. On reversing the venous hypertension a significant increase of CD11b expression was noted in both neutrophils and monocytes (p < 0.001 and p < 0.01, Wilcoxon). Surface L-selectin expression, however, showed a significant sustained fall in both neutrophils and monocytes (neutrophils, p = 0.05 and p = 0.02; monocytes, p = 0.04 and p = n.s., Wilcoxon) throughout the experiment. There was a significant rise in soluble L-selectin in the plasma following venous hypertension (p < 0.001, Wilcoxon).

Conclusion:

This study demonstrates both neutrophil and monocyte activation in the microcirculation of normal volunteers in response to short-term venous hypertension.