Identification of a serpin specifically expressed in multipotent and bipotent hematopoietic progenitor cells and in activated T cells

We have identified a gene that has a high level of mRNA expression in undifferentiated, multipotential hematopoietic cells (FDCP-Mix) and that downregulates both transcript and protein, as these cells are induced to differentiate into mature myeloid cells. Sequence analysis of this gene has identified it as a serine protease inhibitor EB22/3 (serpin 2A). Constitutive expression of serpin 2A in FDCP-Mix cells was associated with an increase In the clonogenic potential of the cells and with a delay in the appearance of fully mature entiation when compared with control cells, Serpin 2A was also found to be expressed in bone marrow-derived bipotent granulocyte macrophage progenitor cells (GM-colony forming cell [CFC]), but not in erythrocyte progenitor cells from day 15 fetal liver. Expression of serpin 2A also showed a marked up regulation during the activation of cytotoxic suppressor CD8(+) T cells, with a clear lag between the appearance of transcript and detection of protein. (C) 1997 by The American Society of Hematology.