Kinetics of B, CD4 T, and CD8 T cells infused into humans: estimates of intravascular:extravascular ratios and total body counts.

Little is known about the rate of T and B cell traffic from blood to extravascular compartments or about the steady-state distribution of T and B cells between intravascular and extravascular compartments in humans. We quantitated circulating T and B cell subsets before and during the first 24 h after the infusion of an allogeneic or syngeneic peripheral blood stem cell graft (containing approximately 10(10) lymphocytes) into 10 patients conditioned with chemotherapy and/or total body irradiation. For all lymphocyte subsets measured, <15% of the infused cells were present in the blood at the end of the 0.5-h infusion and <3% of the infused cells were present in the blood 1 h later. Thereafter, CD4 T cell counts plateaued at approximately 1% and CD8 T cell counts at < or = 0.4% of the infused cells, whereas B cell counts declined slowly (1.5% of the infused B cells were present in the blood at 2 h and 0.3% at 24 h postinfusion). We conclude that the rate of lymphocyte traffic from blood to extravascular spaces can be extraordinary (approximately 10(10) lymphocytes can leave blood within 0.5 h) and that at steady state the blood contains approximately 1% total body CD4 T cells, < or = 0.4% total body CD8 T cells, and approximately 1.4% total body B cells. By inference, an average-size person may carry a total of approximately 4.1 x 10(11) CD4 T cells, > or = 4.5 x 10(11) CD8 T cells, and approximately 1.0 x 10(11) B cells.