Reconstitution of the cellular immune response after autologous peripheralblood stem cell transplantation in patients with non-Hodgkin's lymphoma

Peripheral blood stem cell (PBSC) transplants may be depleted of lymphoid p rogenitors, thereby disabling the cellular immune response against viral pa thogens after autologous PBSC transplantation (PBSCT). To monitor the cellu lar immune reconstitution after autologous PBSCT, we investigated the cytol ytic activity (CLA) of peripheral blood T lymphocytes against Epstein-Barr virus (EBV) in 13 patients with non-Hodgkin's lymphoma or multiple myeloma. The individual EBV-directed CLA (EBV-CLA) was determined by calculating th e number of cytolytic effector cells in 10(6) T cells needed to lyse 25% of autologous EBV-transformed B-lymphoblastoid cells, expressed as lytic unit s (LU25). During the first 6 months after PBSCT, the EBV-CLA was only 14.6% of the response of healthy controls (median 4.8 vs. 32.9 LU25). Thereafter , the EBV-CLA increased to 28.15 LU25 (median) or 86% of healthy controls. Monthly follow-up analyses in five selected patients showed that the EBV-CL A was barely detectable at 4 weeks and recovered at 8-12 weeks after PBSCT in four out of five patients. Effector cells consisted mostly of CD8-positi ve T lymphocytes, with small CD4- and CD3/CD56-positive lymphocyte fraction s. These results suggest that the reconstitution of the cellular immune res ponse against EBV takes 8-12 weeks after autologous PBSCT.