MCcp increase in the bone marrow following mast cell depletion of the peritoneal cavity . MCcp were isolated from bone marrow using sequential isolation with mAb AA4 conjugated magnetic beads followed by mAb BGD6 conjugated magnetic beads as detailed in the Materials and Methods. (A) By electron microscopy this representative MCcp (AA4-/BGD6+) is a small undifferentiated cell with scant cytoplasm and a large nucleus (N). (B) Lysis of peritoneal mast cells results in an increase in the percentage of AA4-/BGD6+ MCcp in the bone marrow. The average of 6 independent experiments ± SD is shown.