Recovery kinetics after chemotherapy and circulating mononuclear cells expressing the CD34 antigen in pediatric cancer patients.

Hematopoietic progenitor cells collected from the peripheral blood are capable of restoring hematopoiesis after myeloablative therapy. The numbers of circulating mononuclear cells expressing the CD34 antigen were calculated and the colony-forming capacity was determined in 26 blood samples, which were drawn during rapid rise of leukocytes after chemotherapy cycles that were followed by aplasia. Culture assay after 14 days revealed a median 507 (210-2029) myeloid progenitors (CFU-GEMM/GM) per 10(5) nucleated cells (NC) in 13 CD34-positive samples, and only a median 76 (9-224) in 13 CD34-negative ones (p less than 0.001). Median 343 (175-2450) erythroid burst-forming units (BFU-E) per 10(5) NC were detected in the CD34-positive samples, whereas only 72 (10-315) per 10(5) NC were found in the negative ones (p less than 0.01). The percentage of CD34-positive cells clearly correlated with the growth of CFU-GEMM/GM and BFU-E (p less than 0.01). The content of CD34-positive cells in circulation was determined within 120 min by FACS analysis and predicted colony-forming capacity of circulating mononuclear cells. These observations will help to select the optimal individual days for leukaphereses.