Factors affecting lymphocyte subset reconstitution after either related orunrelated cord blood transplantation in children - a Eurocord analysis

Immune recovery after cord blood transplantation (CBT) is of concern owing to the low number of lymphocytes transferred with the graft and their immat urity. Risk factors influencing lymphocyte subset reconstitution related to disease, patient, donor and transplant were studied in 63 children (< 16 y ears), given either related (n = 14) or unrelated (n = 49) CBT for malignan t (n = 33) or non-malignant diseases (n = 30). Only children with sustained myeloid engraftment were analysed. Absolute numbers of T (CD3(+), CD4(+), CD8(+)), B and natural killer (NK) cells were reported 2-3, 6, 9, 12 and 12 -24 months after CBT. Median patient age was 4.0 years (0-15) and median fo llow-up was 23 months (1.7-61.0). Twenty-six patients received human leucoc yte antigen (HLA)-matched CBT and 37 received HLA-mismatched CBT. The media n number of nucleated cells (NCs) collected/recipient weight was 6.1 x 10(7 )/kg. In this selected population, the estimate 2 year survival was 85%. Ly mphocyte reconstitution (defined as the median time to reach the normal val ue of age-matched healthy children) was 3, 6 and 8 months for NK, B and CD8 (+) cells, while it was 11.7 months for both CD3(+) and CD4(+) lymphocytes. In the multivariate analysis, factors favouring T-cell recovery were: rela ted donor (P = 0.002); higher NCs/kg (P = 0.005) and recipient cytomegalovi rus (CMV)-positive serology (P = 0.04). Presence of acute graft-versus-host disease (GVHD) delayed T-cell recovery (P = 0.04). To summarize, in childr en with sustained myeloid engraftment the concern that lymphocyte recovery after CBT could be delayed does not appear to be substantiated by our resul ts.