Text Box: RECONSTITUTION OF PERIPHERAL BLOOD LYMPHOCYTE SUBSETS IN THE LONG-TERM SURVIVORS OF CHILDREN WITH ACUTE LYMPHOBLASTIC LEUKEMIA Zhang RD, Wu, MY Beijing Children’s Hospital, Beijing, China Objective: To study the recovery of peripheral blood lymphocytes (PBL) subset after finishing chemotherapy to clarify the reconstitution of the immune system in ALL. Methods: Thirty-eight children with ALL (standard risk) in post-chemotherapy were entered into the study. There were 21 males and 17 females; and the time after completion of chemotherapy ranged from 0.5 to 95 months (median 33.9 months). PBL subsets were analyzed by flow cytometry with the use of monoclonal antibodies against CD3, CD5, CD4, CD8, CD16+56, CD19, CD28, CD29, CD45RA, CD45RO, HLA-DR. Results: There was a significant positive relationship between the number of CD3+, CD3+CD4+, CD4+CD45RA+ cells. And the duration of time post-chemotherapy and a negative relationship between the percent of CD3+CD4-CD8-, CD3+CD4-CD8+, CD8+CD28- cells and the duration of time post-chemotherapy. Conclusion: These findings demonstrate that patients in CR have a low number of CD3+, CD3+CD4+, CD4+CD45RA+, T cells at an early period after chemotherapy and each subsets recovered to a normal level in 1 or 2 years. There were high DR+ T cells for a long time, suggesting that activated T cells may play a role in the immune system after chemotherapy. 1164