Recovery of blood T-cell subsets after chemotherapy for childhood acute lymphoblastic leukemia.

Recovery of cell-mediated immunity after cessation of chemotherapy for childhood acute lymphoblastic leukemia (ALL) was investigated in 14 children to monitor the duration of immune deficiency. The numbers of blood T cells and their subsets were analyzed at 0, 1, 3, 6, 9 and 12 months after discontinuation of therapy with monoclonal antibodies and flow cytometry. The total T-cell count was low at cessation but normalized at 1 to 3 months, whereas the T-cell subsets CD4+, CD8+, CD4+Leu8-, and CD4+CD45RA+ recovered differently. In children ages 3 to 6 years, the numbers of CD4+ cells and their subsets were normal at cessation, whereas in children ages 7 to 18 years, CD4+ and CD4+Leu8+ cell counts normalized only at 6 months. The numbers of CD8+ cells or activated T cells were not increased and the CD4+/CD8+ ratio was not inverted, unlike recovery after bone marrow transplantation. Although the groups showed a mean reversion to normal values by 6 months, there were individual patients who continued to have subnormal values for 1 year after therapy, some of whom exhibited increased susceptibility to infections.