Immunocytochemical identification of immature rat peritoneal mast cells using a monoclonal antibody specific for rat mast cells

The lack of immunological or morphological markers raakes identification of immature mast cells difficult. In the present study we have used a rat mast cell specific monoclonal antibody (mAb AA4) to immunolabel mast cells during repopulation of the peritoneal cavity. Peritoneal cells were collected six days after injection of distilled water and examined by light and electron microscopy. mAb AA4 stained immature mast cells in various stages of maturation including a population of very immature mast cells that could not be identified using conventional staining methods. These cells had virtually no cytoplasmic granules and peripherally located located nuclei. Thus, immunolabeling with mAb AA4 has revealed a population of very immature mast cells not previously reported during repopulation of the peritoneal cavity.