Purpose: To explore modifications in signal mechanisms involving CD11b and leukocyte adhesion in patients under haemodialysis (HD).
Methods: Samples were obtained from uremic patients at baseline, 15 and 120 min of HD from both arterial and venous lines. CD11b expression was studied by flow cytometry. To study signalling mechanisms, CD11b was immunoprecipitated using a specific antibody. Immunoprecipitates were resolved by 8% SDS-PAGE to measure phosphorylation in immunoblots. Leukocyte adhesion was measured after blood perfusion using endothelial cells (EC) as adhesive substrate. Parallel studies were performed with blood from healthy donors.
Results: The percentage of CD11b+ cells increased during HD with a cellulose membrane in the venous line at 15 and 120 min (6.2+/-2.9% and 11.0+/-7.1%) and in the arterial line at 120 min (11.5+/-8.5 vs. 3.1+/-1.0% in control P < 0.05). After 120 min HD, CD11b phosphorylation decreased in leukocytes from both arterial (72.6+/-2.9) and venous lines (51.8+/-6.5) vs. basal samples (119.5+/-15.5 P < 0.005). Control leukocytes showed enhanced adhesion to uremic EC compared with control EC (3.0+/-0.3 vs. 2.3+/-1.0 leukocytes x100 EC(-1) P < 0.05). Uremic leukocyte adhesion was enhanced after HD compared with basal samples 4.2+/-0.2 leukocytes/100 EC in the arterial and 4.4+/-0.3 in the venous line; after 120 min vs 2.3+/-1.0 (P < 0.005).
Conclusion: Leukocyte activation during HD through a cellulose membrane occurs with decreases in CD11b phosphorylation. Activation also induces increases in CD11b expression associated with enhanced leukocyte adhesion to uremic endothelial cells.