Immune reconstitution after transplantation of autologous peripheral CD34+ cells: analysis of predictive factors and comparison with unselected progenitor transplants.

The recovery of lymphocyte count, CD4+ and CD8+ T-cell subsets, natural killer (NK) cells and CD19+ B-cells was evaluated in a cohort of 15 patients receiving autologous CD34+ peripheral blood progenitor cells (PBPCs; group A) for haematological malignancies and in 20 patients transplanted with autologous unselected PBPCs (group B). Lymphocyte count recovered in both patient cohorts, being significantly lower in group A than in group B 1 (P = 0.008) and 2 months (P = 0.0035) after progenitor cell infusion. The repopulation of CD3+ T-cells occurred more rapidly in group B than in group A (P = 0.034 on week 4); CD19+ B-lymphocytes did not return to reference ranges in either group of patients. The count of CD4+ T-lymphocytes remained < 200/microl during the study period in patients transplanted with CD34+ PBPCs, significantly lower than group B levels (P = 0.034 and P = 0.021 on weeks 4 and 8 respectively). CD8+ T-cells increased rapidly in both groups; thus, the CD4 to CD8 ratio was severely reduced. CD4+ and CD8+ T-cells displayed an activated phenotype in both groups of patients, co-expressing the HLA-DR antigen throughout the study period. NK cells followed a similar repopulation kinetics in both study groups, although their expansion was greater in group B than in group A (P = 0.014 on week 4). In the CD34+ group, post-transplant administration of granulocyte colony-stimulating factor predicted a faster lymphocyte recovery in multivariate analysis (P = 0.025); interestingly, the amount of passively transferred lymphocytes correlated inversely with time to achieve a lymphocyte count > 0.5 x 10(9)/l (r = -0.63, P = 0.01). Further investigations are necessary to characterize T-cell competence after transplantation of CD34+ PBPCs.