The reconstitution of CD45RB(hi)CD4(+) naive T cells is inversely correlated with donor age in murine allogeneic haematopoietic stem cell transplantation

A high incidence of opportunistic infections after unrelated bone marrow tr ansplantation has been reported. Delayed lymphocyte recovery may be associa ted with opportunistic infections. Immune reconstitution is influenced by r ecipient age and graft-vs-host disease (GVHD). In fact, children develop GV HD less frequently than adults. However, the role of donor age is largely u nknown. We examined the effect of donor age on lymphocyte reconstitution af ter transplant. Three-month-old BALB/c recipient mice were lethally irradia ted and transplanted with allogeneic haematopoietic stem cells from A/J don or mice of different ages, ranging from 0 d to 12 months. The recovery of a bsolute lymphocyte counts and those of CD3(+) T cells, CD4(+) T cells and C D45RB(hi) CD4(+) naive T cells in the early post-transplant period correlat ed inversely with donor age. Recipient mice transplanted with haematopoieti c stem cells from younger donors showed significantly higher survival rates and mitogenic responses than adult donors. As T cells, especially CD4(+) n aive T cells, play an important role in host defence, faster recovery of CD 4(+) naive T cells in younger donors may contribute to reduced mortality in the early post-transplant period. The results suggest that it could be bet ter to choose a younger donor if sufficient cell dose is available.