Involvement of interleukin-2 in immunologic reconstitution following bone marrow transplantation in mice.

Allogeneic or autologous bone marrow transplantation (BMT) is a curative form of treatment for patients with a variety of hematologic disorders. Impaired immune reconstitution following BMT may seriously impede successful outcome. In this study, the immune function of spleen and thymus was investigated in mice exposed to myeloablative total-body irradiation followed by syngeneic BMT. The T cell mitogen-induced proliferation of both splenic and thymic cells was delayed. Spleen cells started to respond only after 21 days, whereas thymic cells remained unresponsive. Kinetic analysis of surface markers revealed the early appearance of spleen cells with the CD3+CD4-CD8- phenotype, and the thymus, despite a low total number of cells, displayed fast recovery of CD3+CD4+CD8+. At the level of mRNA, a mild decrease in interleukin-2 (IL-2) induction following phytohemagglutinin activation of spleen cells correlated with a decrease in IL-2 secretion for only the first 2 weeks following transplantation. The early restoration of IL-2 implies other avenues for investigation of the immune dysfunction and its correction following syngeneic BMT.