Keisuke Aoyama

Limitin : An interferon-like cytokine that preferentially influences B-lymphocyte precursors

We have identified an interferon-like cytokine, limitin, on the basis of its ability to arrest the growth of or kill lympho–hematopoietic cells. Limitin strongly inhibited B lymphopoiesis in vitro and in vivo but had little influence on either myelopoiesis or erythropoiesis. Because limitin uses the interferon α/β receptors and induces interferon regulatory factor-1, it may represent a previously unknown type I interferon prototype. However, preferential B-lineage growth inhibition and activation of Janus kinase 2 in a myelomonocytic leukemia line have not been described for previously known interferons.

Stromal cell CD9 and the differentiation of hematopoietic stem/progenitor cells.

CD9 belongs to the tetraspan family of proteins that facilitates the regulation of cell proliferation, motility, and adhesion. In mouse hematopoietic organs, CD9 is expressed by myeloid and stromal cells. Although the precise mechanisms are not clear, antibody ligation of CD9 on stromal cells regulates the adhesion between stromal cells and hematopoietic stem cells, the production of myeloid cells in long term bone marrow cultures and the differentiation of hematopoietic stem cells. A 100 kD protein co-precipitated with CD9 is distinct from several previously reported CD9-associated molecules with respect to size and distribution. Identification and analysis of this interesting protein may clarify the molecular mechanisms through which CD9 bearing stromal cells control the differentiation of hematopoietic stem cells and/or allow them to maintain their vital self-renewal capacity.