Immune recovery after bone marrow transplantation.

The donor-derived immune system that forms after bone marrow transplantation (BMT) takes as long as 2 years to develop in healthy BMT recipients. Soon after BMT, GVHD and its treatment increase the susceptibility of the recipient to overwhelming infections, and they retard the development of the immune system. The new system develops from a primitive state characterized by cytotoxic and suppressive functions and progresses to a mature state characterized by the development of specialized lymphocyte functions such as lymphokine production, proliferation, and expression of growth factor receptors. These specialized functions develop in healthy long-term recipients, whereas the same functions may be absent or impaired in those who develop chronic GVHD.