Reconstitution of peripheral blood lymphocyte subsets in the long-term disease-free survivors of patients with acute myeloblastic leukemia

Abstract

The number of long-term survivors of patients with acute myeloblastic leukemia (AML) has increased as a result of the progress of chemotherapy. We examined the recovery of peripheral blood lymphocytes (PBL) subset after chemotherapy to clarify the reconstitution of the immune system in AML. Thirty patients with AML in complete remission (CR) were entered into the study. There were 12 males and 18 females; one M0, six M1, 14 M2, three M3, two M4 and four M5 according to FAB classification. The age ranged from 21 to 78 years (median age, 46 years) and the duration of disease-free survival after completion of chemotherapy ranged from 5 to 122 months (median, 35 months). The chemotherapy was performed according to the protocol designed by the Japan Adult Leukemia Study Group (JALSG). PBL subsets were analyzed by flow cytometry with the use of monoclonal antibodies against CD2, CD3, CD4, CD5, CD8, CD16, CD20, CD45RA, CD56, CD57 and HLA-DR. There was a significant positive relationship between the absolute number of CD4⁺, CD45RA⁺ CD4⁺ cells and the duration of time post-therapy and a significant negative relationship between %CD5⁺ B, CD56⁺ cells and the duration of time post-therapy. The appearance of autoantibodies (rheumatoid factor and anti-DNA antibody) tended to increase after 2 years, however, there was no relationship between CD5⁺ B cells and the frequency of rheumatoid factor. These findings demonstrate that patients in CR have a low number of CD4⁺ and CD45RA⁺ CD4⁺ T cells at an early period after chemotherapy and that each subset recovered to a normal level in 2 years. %CD5⁺ B and CD56⁺ cells gradually decreased and returned to their normal level after 4 years. There were high numbers of DR⁺ T cells and NK cells for a long time, suggesting that activated T cells and NK cells may play a role in the immune surveillance system after chemotherapy.