Phenotypic and functional lymphocyte recovery after CD34(+)-enriched versus non-t cell-depleted autologous peripheral blood stem cell transplantation

To determine the effect of CD34(+) selection on immune recovery after high- dose chemo/radiotherapy in the setting of autologous stem cell transplantat ion (ASCT), we analyzed quantitative and qualitative lymphocyte reconstitut ion for up to 1 year post-transplantation in 27 consecutive adult patients receiving either CD34(+)-enriched or unmanipulated autologous stem cell (SC ) grafts. Pretransplant immunological parameters were identical for both tr eatment groups. Total lymphocyte counts as well as CD3(+) T cells provided a similar course of recovery in both cohorts, returning to baseline values within the first 3 months. There were no significant differences in the rec onstitution kinetics of CD4(+), CD8(+), CD45RA(+), and CD45RO(+) T cells. C D4(+) and CD45RA(+) T cells between the two groups were significantly decre ased within the first 6 months, returning to pretransplant baseline values by 1 year. Although within the first 3 months the majority of CD3(+) cells were activated as demonstrated by expression of HLA-DR, we observed a signi ficant loss of CD25(+) T cells in both groups within the first 6 months. B cell numbers returned to baseline values within 3 months but in vivo B cell function measured by serum immunoglobulin M (IgM) and IgA levels did not r ecover as early as 6 months post-transplantation. T cell function measured by proliferation in response to the lectins phytohemagglutinin (PHA) and Co ncanavalin A (ConA) and to alloantigens in the mixed lymphocyte reaction (M LR) was significantly impaired, but tended to return to pretransplant basel ine values by 1 year. Although preliminary, our results provide strong evid ence that T cell depletion (TCD) by CD34(+) enrichment using the CellPro de vice does not result in delayed phenotypic immune reconstitution after auto logous peripheral blood stem cell transplantation (PB-SCT). Even in the abs ence of a high thymic T cell regenerative capacity in adults, T cell number s and subset distributions were restored within the time frame studied. T a nd B cell function, however, remained significantly impaired for a prolonge d period of time (>6 months after SCT) with a more profound defect in patie nts autografted with CD34(+)-enriched SC.