Immune reconstitution more than one year after allogeneic haematopoietic stem cell transplantation

Duration of immune deficiency post haemopoietic stem cell transplantation (HSCT) is highly variable. We enumerated circulating natural killer cells & lymphocyte subsets post transplant in association with stem cell source, chronic graft versus host disease (cGVHD), conditioning and recipient age. We studied 63 patients more than one year post transplant. Peripheral blood samples were analysed using flow cytometry. The absolute counts of T & B lymphocytes, NK cells, CD4+ & CD8+ T cell subsets were determined. Results were correlated with graft, host & transplant related factors. Of the 63 patients studied, 43(68%) received sibling allografts and 20(32%) matched unrelated transplants for predominantly malignant haematological conditions. The median age at transplant was 43 years (range 19-66 years). The median time of sampling post HSCT was 42 months (12-262 months). Twenty three (37%) had a reduced intensity transplant while 37 of the remaining 40 received TBI based myeloablative conditioning. Twenty five (40%) received Alemtuzumab (Campath) pretransplant. 38(60%) received haemopoietic progenitor cells collected by apheresis (HPC-A). Of the 63 patients, 8(13%) were lymphopenic; 5 of whom had cGVHD. Ten (16%) had low NK cells. 29 (46%) patients had an inverted CD4/8 (5years post transplant. Persistent CD4 lymphopenia was seen in 12 patients, 3 of whom were >5 years post transplant (although more common in the group with cGVHD, the difference was not statistically significant). Fewer patients in the group receiving HPC-A had low NK and T lymphocyte numbers compared with recipients of marrow stem cells (p