Concentration of activated T lymphocytes in extracorporeal blood circulation for plasma separation

To investigate whether the proportion of activated T lymphocytes changes in an extracorporeal blood flow, we compared paired samples collected at the inlet and outlet lines of an artificial circuit for plasma separation, using a dual-immunofluorescence flow cytometric technique. In our series of materials from patients with rheumatoid arthritis or systemic lupus erythematosus, the percentages of HLA-DR-positive cells in both CD4+ (P less than 0.01, n = 6) and CD8+ (P less than 0.05, n = 10) subsets were significantly increased in the outlet lines compared with the inlet lines, suggesting that activated T lymphocytes pass through an extracorporeal blood circuit more easily than resting T lymphocytes.