T Cells of Patients with Myelodysplastic Syndrome Are Frequently Derived From the Malignant Clone

Abstract 2808

T cell clonality is a common finding in myelodysplastic syndromes (MDS), but is believed to be a reactive phenomenon. We compared copy number abnormalities in matched CD34⁺ progenitor cells and CD3⁺ T cells from 40 MDS patients by array comparative genomic hybridization. In 9 of 14 patients with large copy number variants, we detected the same aberration in CD34⁺ and CD3⁺ cells. Chromosome 20q (2 patients), isodicentric × chromosome (2 patients), trisomy 8 (2 patients), 11q abnormalities (1 patient), deletion 5q (1 patient) and partial trisomy 9 with trisomies 19 and 22 (1 patient) were detected in the CD34⁺ and CD3⁺ cells of these patients. The presence of deletion 20q, trisomy 8 and deletion of chromosome arm 11q in the T cells of 3 patients was confirmed by FISH. Multiplex PCR for TCR γ rearrangement was performed on 6 of the 14 MDS patients with large copy number variants. T cell clonality was detected in 3 of 4 and oligoclonality in 1 of 4 patients when the copy number variant was present in both CD34⁺ and CD3⁺ cells. In contrast, the 2 cases lacking the CD34⁺ copy number variant in the CD3⁺ population were polyclonal at the TCR γ locus. These data suggest that in a large proportion of MDS at least a proportion of the T cells are part of the malignant clone, and that CD3⁺ cells do not represent an appropriate patient normal control for genome-wide studies.