Mast Cells and Oral Inflammation

Two human mast cell types were identified by immunohistochemical techniques in skin, lung, and small intestine. One type contains the neutral proteases, tryptase and chymotryptic proteinase, and is termed the TC mast cell. The second type contains only tryptase and is termed the T mast cell. Both types are fixed better by Carnoy's fluid than by formalin. The percentage of mast cells accounted for by the T type was 12 in skin; 98 in mucosa and 13 in submucosa of small intestine; and 77 in bronchial/bronchiolar subepithelium, about 97 in bronchial/bronchiolar epithelium, and 93 in alveoli of lung. Dispersed lung cells contained 90% T mast cells. The mean area of TC mast cells (76 micron2) was slightly larger than that of T mast cells (66 micron2); however, there was such extensive overlap that individual mast cells belonging to different types could not be distinguished on the basis of size. The recognition of human mast cell types with distinct protease compositions suggests a higher level of complexity of human mast cell-mediated reactions than heretofore appreciated.

One decade ago, vascular endothelium was commonly considered a "non-stick" lining of blood vessels that functioned only to prevent blood coagulation and to separate the vascular space from tissues. By comparison to many other cell types, endothelial cells were thought to be less active, less complex, and less interesting. Since that time, research concerning the endothelium has expanded dramatically and produced a new image of the vascular lining as an active participant in a wide variety of pathophysiological processes, including inflammation and immunity. Nowhere has the excitement been more intense than in the study of the molecular mechanisms of leukocyte adhesion to endothelium. Recent efforts resulted in the identification, characterization, and cloning of multiple endothelial cell-surface glycoproteins that support adhesion through an interaction with specific ligands (or counter-receptors) on leukocytes. The selectins, two of which are found on endothelium and one on leukocytes, support adhesion through the recognition of carbohydrates. Endothelial members of the immunoglobulin superfamily including ICAM-1 and VCAM-1/INCAM-110 bind to leukocyte cell-surface integrins. In various combinations, these and other molecules support leukocyte adhesion to the vessel wall and extravasation, key steps in our response to infection and tissue injury.