SUCCESSFUL FORMATION OF A CHIMERIC HUMAN THYMUS ALLOGRAFT FOLLOWING TRANSPLANTATION OF CULTURED POSTNATAL HUMAN THYMUS

Transplantation of cultured postnatal human thymus was performed in a patient with complete DiGeorge syndrome. Biopsy of the graft 3 mo afte r implantation revealed normal CD1(+) thymocytes in thymic cortical ep ithelial regions and CD1(-) thymocytes in thymic medullary epithelial regions, respectively. HLA analysis of graft thymocyte and thymic micr oenvironment components demonstrated that developing thymocytes and th ymic macrophages were recipient derived, while thymic epithelial compo nents were of donor origin. The patient, who initially had no T cells and had profoundly defective T cell function, developed normal T cell responses to mitogens and Ags, tolerance to donor in a mixed lymphocyt e reaction, and normal Ab titers after tetanus toroid and pneumovax im munization. Thug transplantation of cultured postnatal human thymic ti ssue in humans can form functional chimeric thymic tissue, and may pro vide a strategy to reconstitute the peripheral T cell pool in select c ongenital and acquired immune deficiency syndromes.