en Pediatric Hematology & Oncology Pediatric Hematology & Oncology پژوهشي Original Article Objective: To study whether the generated CD1a positive cells belong to the leukemic cells among patients with juvenile myelomonocytic leukemia. Materials and Methods: We used mononuclear cells from 3 patients with juvenile myelomonocytic leukemia, from which two had monosomy 7. The mononuclear cells from these patients were cultured in RPMI/10%FCS without adding exogeneous growth factors for 7 days. At day 7 the cultured cells were harvested and analyzed using antibodies against Ki 67, CD20 and CD1a. Additionally the cultured cells were analyzed using antibodies against CD1a and CD20 and chromosome 7 specific DNA probe, using combined fluorescence immunophenotyping and interphase cytogenetic techniques. Results: The immunocytochemistry assay demonstrated that a high number of cells were in proliferation status, which was determined by antibody against proliferation associated nuclear protein ki 67. The percentage of Ki 67 positive cells was between 24% and 38% respectively. The percentage of CD1a positive cells was between 8% and 31% and the percentage of CD20 positive cells was between 5% and 12% respectively. The fluorescence immunophenotyping and interphase cytogenetic analysis showed that nearly all CD1a positive cells of one patient with monosomy 7 had one chromosome 7, whereas in other patient with monosomy 7, the amount of CD1a positive cells having only one chromosome 7 was approximately 11%. Furthermore, the combined immunophenotyping and cytogenetic analysis showed that the CD20 positive cells in all patients had normal karyotype. Conclusion: Our results suggest that CD1a positive cells generated by mononuclear cells from patients with juvenile myelomonocytic leukemia in vitro most probably belong to the leukemic cells. Since monosomy 7 could not be detected in all CD1a positive cells in juvenile myelomonocytic leukemia patients with monosomy 7, it is to assume that monosomy 7 is a secondary event in the pathophysiology of juvenile myelomonocytic leukemia. Keywords: Leukemia, mononuclear cells, CD1a antigen, chromosome 7, monosomy, cell proliferation, myelomonocytic, juvenile Leukemia, mononuclear cells, CD1a antigen, chromosome 7, monosomy, cell proliferation, myelomonocytic, juvenile 111 118 http://ijbc.ir/browse.php?a_code=A-10-1-1&slc_lang=en&sid=1 P Shayan 10031947532846001164 10031947532846001164 Yes M Izadyar 10031947532846001165 10031947532846001165 No B Eckert 10031947532846001166 10031947532846001166 No