COMPLEMENT-CLS, A CLASSICAL ENZYME WITH NOVEL FUNCTIONS AT THE ENDOCHONDRAL OSSIFICATION CENTER - IMMUNOHISTOCHEMICAL STAINING OF ACTIVATEDCLS WITH A NEOANTIGEN-SPECIFIC ANTIBODY

The secondary ossification center of 14- to 16-day-old hamster tibiae was examined immunohistochemically with active and inactive Cls-specif ic antibodies, RK5 and RK4, respectively. At the ossification center, chondrocytes differentiate from proliferating and hypertrophic to dege nerating stages, and their site is occupied by the bone marrow. Cls wa s strongly immunostained in hypertrophic chondrocytes. In order to dis cover whether Cls is activated at a particular site, the cartilage was immunostained with RK5 and RK4. RK5 mainly reacted with degrading mat rix around invading vessels. In contrast, RK4 strongly stained hypertr ophic chondrocytes. Immunoelectron microscopy revealed Cia on degradin g fragments of chondrocytes and fibers of cartilage matrix. Decorin, o ne of the major matrix proteoglycans, was dose and time dependently de graded by Cls. Type IT collagen and type I gelatin were also degraded. Articular cartilage from patients with rheumatoid arthritis was posit ively immunostained (11/12 cases) with an anti-Cls monoclonal antibody (mAb) PG 11, whereas normal articular cartilage (5/5 cases) was negat ive, suggesting Cls participation in the etiology of rheumatoid arthri tis.