Immune reconstitution after haploidentical hematopoietic cell transplantation: impact of reduced intensity conditioning and CD3/CD19 depleted grafts.

Haploidentical hematopoietic cell transplantation (HHCT) using CD34 selected grafts is complicated by slow engraftment and immune reconstitution. Engraftment and immune reconstitution might be improved using CD3/CD19-depleted grafts and reduced intensity conditioning (RIC). We report on 28 patients after HHCT with CD3/CD19-depleted grafts using RIC, which were prospectively evaluated for engraftment and immune reconstitution. Engraftment was rapid with full chimerism reached on day +15 after HHCT. T-cell reconstitution was delayed with a median of 205 CD3+ cells/μl, 70 CD3+CD4+ cells/μl and 66 CD3+ CD8+ cells/μl on day +100, respectively. A skewed T-cell receptor-Vβ repertoire with oligoclonal T-cell expansions to day +100 and normalization after day +200 was observed. B-cell reconstitution was slow with a median of 100 CD19+ CD20+ cells/μl on day +150. Natural killer (NK) cell engraftment was fast reaching normal values on day +20. An increased natural cytotoxicity receptor and NKG2A, but decreased NKG2D and KIR expressions were observed on NK cells until day +100. We observed a positive impact of donor lymphocyte infusions on immune reconstitution. In conclusion, after HHCT, using CD3/CD19-depleted grafts and RIC, T- and B-cell reconstitution is delayed, whereas NK-cell reconstitution occurs early and fast.