Inhibitory effect of murine kidney extracts on mast cells derived from human umbilical cord blood

We examined the effect of aqueous murine kidney extract (MKE) on the growth of mast cells prepared from the liquid culture of human umbilical cord blood CD34(+) cells in the presence of a combination of recombinant human stem cell factor (SCF) and interleukin-6 (IL-6). Cultured cells were mature mast cells that expressed CD 117 antigen on their surface, a specific marker for human mast cell, and they contained 6.53 pg histamine per cell. Adding MKE resulted in a 53% inhibition of mast cell growth and a 40% decrease in histamine content in mast cells in a serum-free liquid culture stimulated by SCF and IL-6. The inhibitory molecule for the growth of human mature mast cells was estimated at about 30 kDa of protein from gel-filtration HPLC. This fraction also inhibited the growth of murine peritoneal cells-derived mast cells. These results suggest that MKE contains regulator(s) that suppress the growth of mast cells and histamine synthesis, and that act beyond species specificity.