Leu-4 (CD3) antigen expression in the neoplastic cells from T-ALL and T-lymphoblastic lymphoma

The authors studied Leu-4 (CD3) antigen localization in the neoplastic cells from six cases with T-ALL, eight with T-lymphoblastic lymphoma (T-LL), and eight with peripheral T-cell lymphomas using immunoelectron microscopy (immuno-EM). Other various monoclonal antibody studies were also performed to detect the stages of differentiation of the neoplastic cells light microscopically. The authors' study indicated that cytoplasmic Leu-4 (cLeu-4) antigen expression appeared at the early stage of thymic T-cells, together with Leu-9 (CD7) and T101 (CD5). Their immuno-EM study also disclosed that the neoplastic cells at the early stage of thymocyte differentiation all had positive results for cLeu-4 but negative results for surface Leu-4 (sLeu-4). The Leu-4 antigen expression in the neoplastic cells at the stage of common thymocyte differentiation with OKT6- (CD1) positive phenotype was variable, showing cLeu-4+sLeu-4-, cLeu-4-sLeu-4+, and cLeu-4+sLeu-4+, depending on the cases investigated. From these results, they suggest that cLeu-4 antigen appears at the stage of early thymocyte differentiation, followed by predominant sLeu-4 expression at the stage of common thymocyte differentiation, and finally simultaneous expression of cLeu-4 and sLeu-4 at the stage of peripheral T-cells.