GAMMA-DELTA T-LYMPHOCYTE REGENERATION AFTER T-LYMPHOCYTE-DEPLETED BONE-MARROW TRANSPLANTATION FROM MISMATCHED FAMILY MEMBERS OR MATCHED UNRELATED DONORS

The recovery of gamma delta T lymphocytes was studied in 31 recipients of T cell-depleted allogeneic bone marrow (BMT) to determine if the d ynamics of reconstitution could be related to graft-versus-host diseas e (GVHD) or other complications of marrow transplantation. Two distinc t patterns of regeneration were apparent. In 12 patients, there was a progressive rise in both the percentage and the absolute number of per ipheral blood gamma delta T cells over the first year post-transplanta tion, but these increases never breached levels found in 14 healthy do nors. Each of the 19 remaining patients had abnormally high proportion s and numbers of gamma delta T cells on at least two occasions followi ng transplantation. The clinical factor that best explained these obse rvations was the frequency of intercurrent infections. Of 19 patients with abnormally increased percentages and numbers of gamma delta T lym phocytes, 18 had one or more episodes of confirmed viral or fungal inf ection, contrasted with only two of 12 in the comparison group (P < 0. 001). There was no significant association of gamma delta T cell recov ery patterns with the presence of GVHD (P = 0.33). We conclude that th e recovery of gamma delta T lymphocytes after marrow transplantation m ay vary. Supranormal levels of this T cell subset are associated with infection and may contribute significantly to cellular immune defenses against fungal or viral disease.