Lymphoid reconstitution after autologous PBSC transplantation with FACS- sorted CD34⁺ hematopoietic progenitors

T-cell and B-cell reconstitution was studied in nine patients who received fluorescence activated cell sorter (FACS)-sorted autologous CD34⁺ hematopoietic progenitor cells (HPC). The mean numbers of T cells (CD3⁺), B cells (CD19⁺) and CD34⁺ HPC administered to each patient were .004, .002, and 1.8 x 10⁶ cells/kg, respectively. After high-dose myeloablative chemotherapy (busulfan, cyclophosphamide, etoposide) CD34⁺ HPC were infused and lymphoid reconstitution was monitored using flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) amplification of VDJ T-cell receptor (TcR) sequences. Restoration of normal numbers of peripheral blood T cells and B cells among recipients of FACS-sorted CD34⁺ HPC was delayed compared to recipients of non-T-cell-depleted PBSC autografts. In both patient groups, the circulating T cells were primarily CD4^-, CD8⁺, αβ TcR⁺, and CD45RO⁺, CD45RA^- during the first 2 months after transplant. Subsequent increases in the frequency of CD45RA⁺ CD45RO^- T cells occurred at 2 to 3 months after transplant, suggesting maturation of CD34⁺ hematopoietic progenitors to 'naive' T cells. Analysis of the TcR repertoire after hematopoietic reconstitution demonstrated decreased diversity of Vβ TcR expression associated with global decreases in the absolute number of total peripheral blood T cells and most Vp TcR⁺ subsets. Three of nine recipients of FACS-sorted CD34⁺ HPC demonstrated significant increases in the percentage of γδ⁺ peripheral T cells and CD5⁺ B cells at 3 to 9 weeks after transplantation, and all patients had transient oligoclonal expansions of T cells expressing specific Vβ TcR. Transplantation with highly purified CD34⁺ HPC results in reduced diversity of the peripheral T-cell repertoire during the early post-transplant period compared with patients receiving unmanipulated or MoAb-depleted transplants.