Improved immune reconstitution after allotransplantation of peripheral blood stem cells instead of bone marrow.

Clinical studies are evaluating possible advantages of allogeneic peripheral blood stem cell transplantation (PBSCT) over bone marrow transplantation (BMT). We compared immune reconstitution after PBSCT (n = 20) and BMT (n = 20) in terms of lymphocyte subset counts and proliferative in vitro responses to mitogens and recall antigens (follow-up: 5 to 11 months posttransplant). Additionally, 10 PBSC harvests and 10 marrow harvests were analyzed for their composition of immunocompetent cells. Compared with BMT patients, PBSCT recipients had PB counts of naive (CD4+CD45RA+) and memory (CD4+CD45RO+) helper T cells and of B cells (CD19+) that were elevated (P < .003, P < .001, and P < .004, respectively) and proliferative responses to phytohemagglutinin (P < .0001), pokeweed mitogen (P < .02), Tetanus toxoid (P < .0005), and Candida (P < .004) that were increased. PBSCT recipients received a mean of 188 (range, 44 to 280) x 10(6) naive helper T cells and 169 (range, 18 to 296) x 10(5) memory helper T cells per kilogram; the corresponding numbers for BMT recipients were 11 (range, 4 to 24) and 10 (range, 1 to 22) x 10(5) cells per kilogram, respectively. The question of whether the documented improved in vitro immune competence after PBSCT is associated with a lower incidence of infectious complications in vivo still needs further study.