Normal cellular prior protein is preferentially expressed on subpopulations of murine hemopoietic cells

We studied the expression of normal cellular prion protein (PrPC) in mouse lymphoid tissues with newly developed mAbs to PrPC. Most of the mature T an d a cells in the peripheral lymphoid organs do not express PrPC. In contras t, most thymocytes are PrPC+ In the bone marrow, erythroid cells and maturi ng granulocytes are PrPC+. Approximately 50% of the cells in the region of small lymphocytes and progenitor cells also express PrPC. Most of these PrP C+ cells are CD43(+), but B220(-), surface IgM(-) (sIgM(-)), and IL-7R(-), a phenotype that belongs to cells not yet committed to the B cell lineage. Another small group of the PrPC+ cell are B220(+) and some of these are als o sIgM(+), The majority of the B220(+) cells, however, are PrPC-. Therefore , PrPC is preferentially expressed in early bone marrow progenitor cells an d subsets of maturing B cells. Supporting this interpretation is our observ ation that stimulation of hone marrow cells in vitro with PMA results in a decrease in the number of PrP(C+)B220(-) cells with a corresponding increas e of sIgM+B220(high) mature B cells. This result suggests that the PrP(C+)B 220(-) cells are potential progenitors. Furthermore, in the bone marrow of Rag-1(-/-) mice, there are an increased number of PrP(C+)B220- cells, and m ost of the developmentally arrested pro-B cells in these mice are PrPC+, Co llectively, these results suggest that PrPC is expressed preferentially in immature T cells in the thymus and early progenitor cells in the bone marro w, and the expression of PrPC is regulated during hemopoietic differentiati on.