Lymphocyte subsets recirculate from blood to lymph at different rates in conscious sheep

Lymphocytes migrate and recirculate continuously between blood and lymph. The current study compared the migratory properties of lymphocyte subsets by labelling lymphocyte surface antigens and analysing simultaneous samples of mesenteric lymph, systemic arterial blood and mesenteric venous blood from conscious sheep. The lymphocyte output in lymph averaged 5.33 +/- 0.89 x 10(6) min-1 (lymph flow rate of 92 +/- 13 microliters min-1, lymphocyte count 61.9 +/- 10.7 x 10(9) l-1, n = 10) and the proportion of cells which carried the CD4 antigen (CD4+) was considerably higher in lymph (46 +/- 3%) than in arterial blood (23 +/- 2%; p < 0.01, n = 9). This increase was paralleled by a small but statistically significant decrease in the percentage of CD4+ cells in mesenteric venous blood (20 +/- 2%), as compared with systemic arterial blood (26 +/- 2%; p < 0.05, n = 6), which is consistent with the hypothesis that CD4+ cells migrate out of the blood vessels, and recirculate through the lymphatics, more readily than other lymphocyte subsets.