Dendritic mast cells in the human nasal mucosa.

Human mast cells can be divided into two subtypes: MCTC cells, which contain tryptase and chymase, and MCT cells, which contain tryptase only. Herein we have used a combination of histamine, tryptase and chymase immunohistochemistry as a novel approach to the study of mast cells. Using this technique, we have discovered a new type of MCTC mast cell in biopsies of the nasal mucosa from healthy subjects and allergic patients. These mast cells have histamine-positive, dendrite-like cellular processes. Some cells have only one slender process, whereas other cells have several long processes extending from different parts of the cell body. Some of the cellular processes divide into two or three terminal 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 cellular processes. The recognition of this extreme heterogeneity may be an important step toward a better understanding of mast cell biology.