ارزيابي بازآرايي باي / اوليگوكلونال ژن هاي ايمونوگلوبولين و گيرنده هاي لنفوسيت T در كودكان ايراني مبتلا به لوسمي لنفوبلاستي حاد از نوع پيش سازهاي B

Evaluation of bi/oligoclonal rearrangement of immunoglobulin and T-cell receptor genes in Iranian children suffering B-precursor acute lymphoblastic leukemia

Background: Clonal gene rearrangement of immunoglobulin and T cell receptor may have mono, bi or oligoclonal pattern. Significance of these patterns were studied at diagnosis and follow up of MRD in many countries, however, similar studies have not been conducted among Iranian patients. We investigated the bi/oligoclonal pattern and their association with quantitative and qualitative parameters especially MRD in Iranian children suffering from B-precursor acute lymphoblastic leukemia. Materials and methods: In our prospective study, bone marrow aspirates of 140 patients with B-precursor ALLs were selected. Mononuclear cells including leukemic blasts isolated by density gradient. Having DNA extracted, hypervariable regions of IgH, IgK, TCR-6 (D62-D63,V62-D63) and TCR-y (Vy, VyI, VyII) were amplified by consensus primers using PCR. PCR products were analyzed after heteroduplex analysis and polyacrylamide gel electrophoresis (silver stain). The DNA sequences were compared and aligned to the sequences homologous for IgH and IgK published by Gene Bank. Bone marrow aspirates of days 14, 28 and 45, as well as months 3, and 6 were treated similarly. Results: IgH gene rearrangements were reported in 114 (90.5%) patients using consensus primers for CDR-III and CDR-I regions (monoclonal:57.8%, biclonal:34.9% and oligoclonal:5.5%). Clonal pattern of IgK-Kde were present in 59 cases (67%) (biclonal:10%). Clonal rearrangement of TCR-y (Vy) and VyI/II were present in 79.3% and 64.9% of patients, respectively, however, only 5% of cases showed biclonal pattern. The VyII rearrangement was the most common (46.8%) type in TCR-y. 47 (45.2%) and 11 (16.6%) patients had V62-D63 and D62-D63 partial gene rearrangements, respectively. Biclonal/oligoclonal pattern were present in 13 (27.7%) and 2 (4.3%) cases with V62-D63 rearrangement. Only one patient had biclonal D62-D63 rearrangement. No significant difference regarding the quantitative and qualitative parameters and MRD was observed between the two groups. Conclusion: Bi/oligoclonal rearrangement of IgH, IgK, TCR-6 (D52-D63,V62-D63) and TCR-y (Vy, VyI, VyII) genes had comparable pattern to other populations. Results of MRD study showed no significant differences between the two groups.