Immune reconstitution and stem cell sources

Hematopoietic stem cells from related and unrelated bone marrow, peripheral blood, and cord blood donors are used for transplantation in children and adults with various malignant and nonmalignant diseases. These cells are tr ansplanted either without manipulation; after the removal of T cells; after selection of CD34+ cells or after a variety of other types of manipulation . Despite the success of hematopoietic stem cell transplantation for many m alignant and nonmalignant diseases, infectious complications remain problem atic. The ability to fight infectious complications, in part, depends upon the rate and completeness of immune reconstitution. The patterns of immune recovery of T cells, B cells, NK cells, and immunoglobulin production are s ummarized for these different stem cell sources. These patterns reaffirm th e critical importance of the thymus for reconstitution of CD4+ T-cell immun ity and illustrate the negative impact of age, T-cell depletion, and graft- versus-host disease on recovery of immunity.