Lineage‐ and differentiation stage‐specific expression of LSM‐1 (LPAP), a possible substrate for CD45, in human hematopoietic cells

CD45, a transmembrane tyrosine phosphatase, is found on almost all nucleated hematopoietic cells and plays a crucial role In lymphocyte activation and differentiation. We recently achieved Isolation of the human LSM-1 (hLSM-1) gene, whose product is a possible substrate for CD45, and we raised antibodies against the hLSM-1 protein. hLSM-1 expression In hematopoietic cells was examined with Northem and Western blot, fluorescence-activated cell sorter, and immunocytochemical analyses. It was found that In the lymphoid lineage, T and B lymphocytes as well as NK cells expressed LSM-1, whereas terminally differentiated plasma cells did not. As for the myeloid lineage, Immature myeloid cells expressed LSM-1, whereas terminally differentiated granulocytes and monocytes did not. In the erythroid lineage, normal erythroblasts expressed very low levels of LSM-1, while erythroid cell lines (K562 and HEL) did not. Megakaryocytes did not express LSM-1. Both CD34 + /CD33 - and CD34 + /CD33 + hematopoietic progenitor cells weakly expressed LSM-1. These results showed that LSM-1 Is expressed in a lineage- and differentiation stage-specific fashion.