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Cartilage destruction in rheumatoid arthritis may be mediated by enzymes of the synovial fluid and by cells of the proliferating pannus tissue. Neutrophilic granulocytes are usually said to affect the cartilage via the synovial fluid, and their local occurrence in the pannus-cartilage border is denied. However, a morphological study on pannus tissue and cartilage by use of histochemistry and immunfluorescence (leucocytes antielastase) exhibited an accumulation of neutrophilic granulocytes in the immediate vicinity of the cartilage in destruction. This result is in contrast to the observation of most investigators reporting studies of the pannus cartilage junction. Experimental datas of the effect of elastase moreover indicate that this enzyme is capable to penetrate into the cartilage and to degrade proteoglycans. Therefore the results show that the occurrence of neutrophilic granulocytes at the pannus-cartilage border is an important phenomenon for understanding the progressive cartilage destruction and that elastase may be at least one enzyme responsible for the degradation of the cartilage matrix.

Elastase, an enzyme in the azurophilic granules of polymorphonuclear cells (PMN), is like other granular PMN proteases characterized by its degradative activity at physiological pH towards native macromolecules as shown in a serum free medium. Joint tissue specimen obtained during elective surgery in cases of various rheumatic conditions were examined in order to elucidate the role of this enzyme during joint cartilage destruction. An indirect immunofluorescence microscopic technique utilizing a rabbit immunoglobulin G preparation raised against purified elastase was used for this purpose. Immunoreactive elastase was seen bound to cells which were recognized as PMN by their nuclear characteristics and staining in a histochemical reaction with naphtol AS-D chloroacetate. PMN were encountered more or less often in the pannus but clearly accumulated in a significant amount at the pannus-cartilage junction in one case of rheumatic monarthritis and three out of four cases with rheumatoid arthritis. This finding shows that PMN--contrary to other descriptions--belong to the morphologic characteristics of inflammatory rheumatic conditions and directly supports the hypothesis that PMN enzymes play an active role in rheumatoid cartilage destruction.