The kinetics of immune reconstitution after human marrow transplantation.

Human marrow transplantation for the treatment of malignant and nonmalignant disorders is becoming an established modality of therapy. As in any aggressive therapeutic modality, the benefits must be balanced with the risks of the therapy. The aggressive chemoradiotherapy used to prepare patients for marrow transplantation creates a transient immunodeficiency disorder postgrafting until the transferred donor marrow reestablishes a competent immune system. Immune reconstitution posttransplant follows a general pattern developing from immature to mature immune functions. Immune reactivity during the first month postgrafting is extremely low. Cytotoxic and phagocytic functions recover by day 100, while more specialized and cooperative functions of T and B cells remain impaired up to one year or more postgrafting. After the first year postgrafting, the various components of the immune systems of most healthy marrow recipients begin to work synchronously, whereas the immune systems of recipients with chronic graft-v-host disease (GVHD) remain crippled. Recent evidence shows that transfer of specific immunity from marrow donors to marrow recipients plays a role in reestablishing immunocompetence. Transferred antigen-specific immunity may explain why more recipients do not die from overwhelming infections.