EXPRESSION OF THE C-KIT LIGAND AND INTERLEUKIN-6 GENES IN MOUSE BONE-MARROW STROMAL CELL-LINES

The expression of c-kit ligand and interleukin 6 (IL-6) genes in mouse bone marrow-derived stromal cell lines was examined using quantitativ e polymerase chain reaction (PCR) analysis based on the design of an i nternal DNA control. The stromal cells studied included the 14F1.1 end othelial-adipocytes that support long-term hemopoiesis and two additio nal cell lines (MBA-1, MBA-13) which do not have this function. All th e cell lines expressed c-kit ligand gene constitutively, and this expr ession was not increased by lectins. On the other hand, the expression of the IL-6 gene was markedly induced in all the lines by lipopolysac charide (LPS) and by phorbol 12-myristate 13 acetate (PMA). The consti tutive expression of c-kit ligand in 14F1.1 cells was the lowest among the three cell lines studied and could be increased by stimulation wi th IL-4. Thus, we observed some quantitative differences among the cel l lines in their expression of cytokine genes. However, the unique cap acity of 14F1.1 cells to support in vitro hemopoiesis cannot thus far be explained solely on the basis of the ability of these cells to secr ete cytokines which are not produced by other stromal cell lines. c-ki t ligand may be necessary, but its presence alone is not sufficient fo r 14F1.1 cells to support prolonged hemopoiesis.