T-cell-specific expression of kinase-defective Eph-family receptor protein, EphB6 in normal as well as transformed hematopoietic cells

Although most kinase-defective growth factor receptor proteins are associat ed with pathogenic conditions, a kinase-defective Eph-family receptor prote in, EphB6, is expressed in normal human tissues. We generated monoclonal an tibodies specific for human EphB6 to characterize its expression on human h ematopoietic cells. A very small population of normal human peripheral whit e blood cells (0.57 +/- 0.07%, n = 12) expressed EphB6, The EphB6-positive cells mere CD2(+), CD7(+), CD3(+) and CD4(+) or CD8(+) lymphocytes, but the y did trot express CD19 or CD11b, In human bone marrow, only 1.5 +/- 0.19% of lymphocytes er;pressed EphB6, Compared with the expression in peripheral lymphocytes, prominent expression of EphB6 protein was demonstrated in CD4 (+)CD8(+) double-positive mouse thymocytes. The T-cell Lineage-specific exp ression was strictly conserved in human leukemia/lymphoma cells. Among T-ce ll-derived leukemia cells, the expression level of EphB6 seemed to decrease with maturation of the cells. These results suggest that EphB6 expression is regulated in T-cell development.