T cell regeneration after allogeneic bone marrow transplantation.

Various T cell subsets were characterized by double immunofluorescent staining using monoclonal antibodies (MoAb) in blood, bone marrow (BM) and tissues of 29 patients after allogeneic BM transplantation (BMT). In an attempt to prevent graft versus host disease (GvHD), 15 patients received cyclosporin A (Cy A). In the remaining 14 patients the BM was pre-incubated with a MoAb, OKT3. The regeneration of T4+ subset was delayed and the level of T8+ cells was abnormally high even 1 year after engraftment. This did not have any predictive value for the appearance of complications such as GvHD or severe viral infections. The number of T8+ cells was lower in the group of patients who received Cy A than in the OKT3 group (0.7 +/- 0.2 vs 1.5 +/- 0.3 X 10(9)/1 at day 90). In contrast to normal individuals, the T4/T8 ratio in both blood and regenerating BM of BMT patients was less than 1. A sizeable subset of circulating T cells expressed the phenotype T8+, T10+, HNK-1+, DR+. Circulating cells of this phenotype were transiently very high (up to 50%) in patients with active GvHD or suffering from severe viral infection. This subpopulation of lymphocytes was not found in the epidermal infiltrate that accompanied GvHD where the predominant phenotype was T8+, T1-, T10-, HNK-1-, DR-. We conclude therefore that after BMT the number and phenotype of circulating T cells reflects the T cell distribution seen in the regenerating BM.