Clonal origin of a T cell lymphoproliferative malignancy

A woman with a T cell lymphoproliferative malignacy and heterozhgosity at the X chromosome-linked locus for glucose-6-phosphate dehydrogenase (G-6PD) isoenzymes was studied to find the clonal origin of her circulating neoplastic T cells. The red blood cells, polymorphonuclear cells, whole mononuclear cells, and T cell-depleted mononuclear cells contained both A and B isoenzymes of G-6-PD. In contrast, the tumor cells, separated by using their capacity to form rosettes with sheep red blood cells, contained only the B isoenzyme of G-6-PD. This observation strongly suggests the monoclonality of this T cell malignancy.