Differences of LAK-activity and IL-2 responsiveness between alpha/beta and gamma/delta T cells which developed after thymus transplantation.

A patient with severe combined immunodeficiency was transplanted with T cell depleted haploidentical bone marrow from his father and was later given a thymic graft from an unrelated donor. alpha/beta and gamma/delta T cells of bone marrow donor origin appeared only after the thymus transplantation procedure. Among the peripheral blood lymphocytes (PBL), gamma/delta T cells comprised 10-20% and most of them were delta TCS1+. The alpha/beta T cells were single positive cells, either CD4+ or CD8+. Expression of CD5, CD7 and CD8 alpha,beta molecules on alpha/beta T cells was reduced. Functional studies showed that gamma/delta T cells proliferated slightly in response to anti-CD3 stimulation, and proliferated well with exogenous IL-2 stimulation, while alpha/beta T cells did not proliferate following mitogenic stimulation even in the presence of IL-2. gamma/delta T cells but not alpha/beta T cells exhibited some LAK activity after culturing with IL-2. Since alpha/beta T cells expressed IL-2R alpha and beta chains after mitogenic stimulation and bound IL-2, the deficit(s) in these cells was considered to occur after IL-2 binding to the IL-2R. These results indicate thymic dependency of both types of T cells and that two types of T cells differed in the acquisition of IL-2 responsiveness during development.