When the peritoneal cavity is depleted of mast cells, both AA4-/BGD6+ and AA4+/BGD6+ cells go to the peritoneal cavity, but only the MCcp (AA4-/BGD6+) home to the bone marrow . MCcp (AA4-/BGD6+) and MCp (AA4+/BGD6+) were immunomagnetically isolated from the bone marrow and labelled with CellTracker Green CMFDA™ or CellTracker Red CMTPX™ respectively. The cells were infused into non-depleted and depleted rats. At 24 and 48 hours after infusion, the peritoneal lavage and bone marrow were collected and examined by FACS for the presence of labelled mast cells. The data is expressed as the number of labelled mast cells/105 cells. The average of 3 independent experiments ± SD is shown.