Increase of bone marrow macrophages and CD8+ T lymphocytes predict graft failure after allogeneic bone marrow or cord blood transplantation

Graft failure (GF) remains an obstacle to survival after allogeneic hematopoietic stem cell transplantation. However, differentiating GF from delayed engraftment (DE) can be difficult. Host CD8(+) lymphocytes have been reported to mediate graft rejection, but the impact of macrophages on DE or GF is yet to be clarified. Peri-engraftment bone marrow (BM) specimens of 32 adult patients with normal engraftment, DE or GF were retrospectively evaluated to identify the potential associations of CD163(+) macrophage and CD8(+) lymphocyte infiltration into BM. The macrophage or CD8(+) lymphocyte number/total nucleated cell number was defined as the Mac ratio and CD8 ratio, respectively. Both DE and GF groups had significantly higher Mac ratios at day 14 than the normal group (P < 0.0001), but no significant difference was observed between the DE and GF groups (P = 1.000). The CD8 ratio at day 14 was significantly higher in the GF than in the normal group (P = 0.005), whereas the CD8 ratios of the DE and normal groups were similar (P = 0.07). A high Mac ratio at day 14 was associated with a risk of DE or subsequent GF. Patients with increased CD8 ratio at day 14 had a further risk of GF. The Mac ratio and the CD8 ratio appear to be well suited for predicting engraftment status.