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 th at downregulates both transcript and protein, as these cells are induc ed to differentiate into mature myeloid cells. Sequence analysis of th is gene has identified it as a serine protease inhibitor EB22/3 (serpi n 2A). Constitutive expression of serpin 2A in FDCP-Mix cells was asso ciated with an increase In the clonogenic potential of the cells and w ith a delay in the appearance of fully mature entiation when compared with control cells, Serpin 2A was also found to be expressed in bone m arrow-derived bipotent granulocyte macrophage progenitor cells (GM-col ony forming cell [CFC]), but not in erythrocyte progenitor cells from day 15 fetal liver. Expression of serpin 2A also showed a marked up re gulation during the activation of cytotoxic suppressor CD8(+) T cells, with a clear lag between the appearance of transcript and detection o f protein. (C) 1997 by The American Society of Hematology.