Objective. To evaluate the potential of using monoclonal antibodies (MAb) 3-B-3(–) and 7-D-4 to detect biochemical markers of altered cartilage metabolism in human arthritides.
Methods. Fifty-five samples of normal articular cartilage (subjects' age range 18 weeks of gestation to 83 years of age) and 89 samples of arthritic cartilage (patients' age range 20–81 years) were collected, and their proteoglycans were extracted and analyzed for the presence of the epitopes recognized by MAb 3-B-3 and 7-D-4.
Results. Native 3-B-3(–) mimotope was expressed at a high incidence in proteoglycans extracted from the cartilage of patients with most of the arthritic diseases examined (osteoarthritis, juvenile rheumatoid arthritis, rheumatoid arthritis, avascular necrosis, and degenerative meniscal tears). Its expression in normal cartilage specimens was very low or absent, occurring mainly in the young, skeletally immature individuals. In contrast, expression of the 7-D-4 epitope was more variable in patients with different arthritides and was also frequently found in normal cartilage specimens. Immunohistochemical analyses with both 3-B-3(–) and 7-D-4 showed strong focal positive staining in superficial areas, where cartilage degeneration, remodeling, and repair were greatest.
Conclusion. The biochemical markers recognized by MAb 3-B-3(–) and 7-D-4 are indicative of altered proteoglycan synthesis and metabolism in human articular cartilage. The data suggest that in human cartilage, the 3-B-3(–) epitope might be a better marker of biochemical changes than the 7-D-4 epitope.