Fig. 4.

Human BMSCs produce increased amounts of IL-6 in vivo in a HDC-and mast cell- dependent manner. Human BMSCs were placed into the peritoneal cavity of control and histamine-deficient (lacking histidine decarboxylase or HDC, a vital enzyme in histamine biosynthesis) mice afer inducing MC degranulation. Six hours later the increase in IL-6 content of the cell-free peritoneal wash was significantly reduced, but still present, in the histamine-deficient mice. Once again this suggests that increased IL-6 production is due to not only histamine but also other MC derived factors. When BMSCs were introduced into MC-deficient mice the same sensitisation/challenge protocol resulted in no IL-6 suggesting the MCs to be responsible for the effect.