Enrichment of c-kit+ Lin− haemopoietic progenitor cells that commit themselves to extrathymic T cells in in vitro culture of appendix mononuclear cells

摘要

The appendix as well as the small intestine have recently been found to carry c-kit⁺ stem cells which give rise to extrathymic T cells. In this study, the properties of c-kit⁺ stem cells in the appendix of mice were further characterized. When appendix mononuclear cells (MNC) were cultured in the presence of stem cell factor, interleukin-3, interleukin-6 and erythropoietin on a methylcellulose culture plate, the population of c-kit^dull Lin⁻ and that of c-kit^hi Lin⁻ cells expanded. Morphological study revealed that these c-kit^hi Lin⁻ cells were basophilic granular cells (possibly mast cells). Both populations of cultured appendix MNC were then injected into severe combined immunodeficient mice or cultured with Tst-4 thymic stroma cells. These in vivo and in vitro studies demonstrated that c-kit^dull Lin⁻ cells were oligopotent haemopoietic progenitor cells which gave rise to extrathymic T cells, while c-kit^hi Lin⁻ cells lacked haemopoietic progenitor cell activity. In contrast to c-kit⁺ stem cells in the bone marrow, those in the appendix did not give rise to myeloid cells and conventional thymic T cells under any of the conditions tested. The present results suggest that the appendix primarily comprises c-kit⁺ cells which give rise to basophilic granular cells and extrathymic T cells and that such c-kit⁺ cells have the ability to replicate themselves in culture in vitro.