Study of the CD3-associated T-cell receptors reveals further differences between T-cell acute lymphoblastic lymphoma and leukemia.

We show further differences between two clinically related entities, T-cell acute lymphoblastic leukemia (T-ALL) and lymphoblastic lymphoma (T-LL), by using several monoclonal antibodies (MoAbs) reacting with either constant or variable regions of T-cell receptors (TcR) alpha beta and gamma delta or with various CD molecules. We analyzed a panel of 15 T-ALL and 15 T-LL selected for their cell surface expression of the CD3 molecules. The results indicated that TcR gamma delta is more frequently used than TcR alpha beta in T-ALL (10 of the 15 patients tested). This is in contrast to the results obtained with T-LL where the vast majority expressed TcR alpha beta (13 of the 15 patients). These findings suggest that the leukemic cells could have a different origin in these two diseases. In addition, analysis of TcR variable regions expressed by the leukemic blasts showed that, in most cases, they had rearranged functional V delta 1 gene segments (8 of 11 patients), whereas in a unique case V delta 2 gene segment was used. Together, these results and those indicating that T-ALL cells coexpress the CD1a, b, and c molecules strengthen the possibility that although these leukemic cells express the CD3-TcR complex at their cell surface, their normal counterparts are not found in peripheral blood.