DENDRITIC MAST-CELLS IN THE HUMAN NASAL-MUCOSA

Human mast cells can be divided into two subtypes: MG,, cells, which c ontain tryptase and chymase, and MC, cells, which contain tryptase onl y. Herein we have used a combination of histamine, tryptase and chymas e immunohistochemistry as a novel approach to the study of mast cells. Using this technique, we have discovered a new type of MG,, mast cell in biopsies of the nasal mucosa from healthy subjects and allergic pa tients. These mast cells have histamine-positive, dendrite-like cellul ar processes. Some cells have only one slender process, whereas other cells have several long processes extending from different parts of th e cell body. Some of the cellular processes divide into two or three t erminal branches, and histamine is sometimes found in small swellings along the course of the processes. Our findings contribute new aspects to the concept of mast cell heterogeneity. Thus, human mast cells may vary not only with respect to mediator content, but also with respect to gross morphologic features such as the presence of dendrite-like c ellular processes. The recognition of this extreme heterogeneity may b e an important step toward a better understanding of mast cell biology .