Injection of distilled water into the peritoneal cavity results in a rapid depletion of mast cells . Two days after injection of distilled water MCp begin to repopulate the peritoneal cavity and by 10 days the repopulation is virtually complete. Mast cells were isolated from the peritoneal lavage by magnetic beads conjugated to mAb AA4. The number of cells free or attached to the magnetic beads was determined by counting the cells in a hemocytometer. The average of 6 independent experiments ± SD is shown.