THYMIC STROMAL CELLS SUPPORT DIFFERENTIATION OF NATURAL-KILLER-CELLS FROM CD34(-MARROW CELLS IN-VITRO() BONE)

Natural killer (NK) cells are CD3(-)CD56(+) lymphocytes characterized by exhibiting non-MHC restricted cytotoxicity. A developmental relatio nship between NK cells and T lymphocytes has been proposed, and, moreo ver, the thymus has been shown to contain NK cell precursors. In this study we utilized an in vitro assay, devised to study T-lymphocyte dev elopment from bone marrow progenitors, to investigate the ability of t hymic stromal cells to support generation of NK cells from CD34(+) bon e marrow cells. CD34(+) cells purified from healthy adults were seeded on adherent thymic stromal cells. The cells emerging after culture we re phenotypically characterized by flow cytometry. We show that lympho cytes expressing the phenotypical characteristics of NK cells were gen erated from CD34(+) bone marrow cells, and that these cells represente d 1% of the cells recovered from the cultures. Furthermore, this was a ccomplished without supplement of exogenous interleukin 2 which is req uired for NK cell differentiation in bone marrow cultures.