A potential role for B cells in suppressed immune responses in cord blood transplant recipients

We evaluated immune reconstitution in 58 adults who received hematopoietic SCTs from allogeneic siblings (allosib), matched unrelated donors (MUD) or cord blood (CB) at 90-day intervals for 1 year post transplant. CB recipients had a higher incidence of infections in the first 100 days compared with allosib and MUD recipients. The number of circulating T cells was lower in CB recipients compared with MUD recipients at 90 days and compared with allosib recipients at 180 days. Spectratype analysis of the TCR Vβ complementarity determining region 3 (CDR3) of patient lymphocytes revealed that the TCR repertoire remained poorly diversified even at 360 days in nearly all patients. In contrast, the number of circulating B cells was significantly elevated in CB recipients compared with allosib recipients throughout the first year post transplant and compared with MUD recipients at 9–12 months. Spectratype analysis of the B-cell receptor V H CDR3 showed that the B-cell repertoire was diversified in most patients by 90 days. CD5 pos B cells from assayed CB recipients expressed intracellular IL-10 early post transplant. Our data suggest that B cells, in addition to T cells, may have a role in impaired immune responses in CB transplant patients.