LOCALIZATION OF ACTIVE AND INACTIVE ELASTASE, ALPHA-1-PROTEINASE INHIBITOR, AND ALPHA-2-MACROGLOBULIN IN HUMAN GINGIVA

Biochemically, there is usually much less elastase activity in gingiva l tissue than in crevicular fluid. The tissue distributions of active and inactive elastase and the endogenous inhibitors alpha-1-proteinase inhibitor (alpha(1)PI) and alpha-2-macroglobulin (alpha(2)M) were the refore compared. Inflamed tissue was obtained from chronic periodontit is patients, and cryostat sections were incubated with the histochemic al elastase substrate MeOSuc-Ala-Ala-Pro-Val-MNA. Adjacent sections we re examined immunocytochemically with antibodies to neutrophil elastas e, alpha(1)PI,alpha(2)M, and leukocyte differentiation antigens. Antig enic elastase was widely distributed in CD15-positive granulocytes in both the epithelium and lamina propria as well as in granulomatous tis sue from infrabony defects. However, there was very limited histochemi cal staining of these cells, and biochemical activity against the equi valent substrate MeOSuc-Ala-Ala-Pro-Val-AFC could be extracted only fr om sections with such staining. The pH optimum and effector response o f the activity in the extracts were, nevertheless, consistent with tho se of leukocyte elastase. The large difference between the total elast ase content of the tissue, as determined immunocytochemically, and the Limited amount of active enzyme, as demonstrated histochemically, ind icated that the majority was in an inactive form. The involvement of t issue inhibitors was suggested by the fact that extracts from sections with no histochemical staining reduced biochemical elastase activity in crevicular fluid. alpha(2)M was found in many fibroblasts and also some CD68-positive macrophages, which additionally contained alpha(1)P I. Both inhibitors appeared to be present extracellularly, since there was significant background staining. Thus, alpha(1)PI and alpha(2)M c ould contribute to the regulation of elastase activity in the gingiva.