The impact of graft composition on clinical outcomes in unmanipulated HLA-mismatched/haploidentical hematopoietic SCT

This study examines the absolute numbers and relative proportions of CD4+, CD8+, CD14+ and CD34+ cells contained in allografts and their impact on early engraftment and later clinical outcomes in 141 patients with hematological malignancies who underwent unmanipulated HLA-mismatched/haploidentical hematopoietic SCT without in vitro T-cell depletion. These patients received G-CSF-primed BM grafts (G-BM) and peripheral blood grafts (G-PB) following a modified regimen of BU/CY 2 plus antithymocyte globulin. Multivariate analysis showed that high CD34+ cell numbers were associated with accelerated plt engraftment (P=0.001). Meanwhile, patients with a higher CD4/CD8 ratio in G-BM (⩾1.16) had a survival disadvantage (P<0.01) and a trend towards relapse (P=0.086) after controlling for disease status. A higher CD4/CD8 was also associated with a significantly increased risk of acute GVHD grades II–IV (P=0.013), even after adjusting for an ABO major mismatch. No aspect of graft composition affected neutrophil engraftment or chronic GVHD. In conclusion, the differences in CD34+ cell dose and the CD4/CD8 ratio in grafts seem to affect engraftment and clinical outcomes; in particular, a lower CD4/CD8 ratio in primed BM graft is associated with a survival benefit.