Heterogeneity of mast cells at multiple body sites. Fluorescent determination of avidin binding and immunofluorescent determination of chymase, tryptase, and carboxypeptidase content.

Human mast cells (MCs) from multiple sites were studied to determine heterogeneity of expression of chymase, tryptase, and/or carboxypeptidase and the binding to avidin. Three immunophenotypes were found: MCs positive for tryptase (MCT), no immunodetectable chymase; MCs positive for tryptase and chymase (MCTC); and MCs positive for chymase (MCC), no immunodetectable tryptase. Chymase-positive MCs also bound avidin and contained carboxypeptidase. In breast skin and parenchyma and axillary lymph nodes > 95% were MCTC; a rare MC in skin and lymph nodes was MCT or MCC. In lung alveoli 91% of MCs were MCT, 8% were MCTC and 1% MCC. In bowel mucosa 58% of MCs were MCT, 35% were MCTC and 7% MCC, whereas in bowel submucosa 83% of MCs were MCTC and 17% MCC. Within esophageal epithelium 38% were MCT and 62% MCTC; whereas, in esophageal subepithelium all were MCTC. This study further documents site-dependent diversity among normal human MCs and recognizes a novel third immunophenotype rich in chymase and relatively deficient in tryptase, the MCC cell.