Cytochemical detection of proteases in synovial fluid of arthritic joints

A cytochemical method can be used to detect neutral proteases in polymorphonuclear leukocytes (PMN cells) in synovial fluid smears obtained from arthritic joints. Using this method, incubation of fixed smears in NaCl-borate buffer causes release of neutral PMN proteases, the enzymatic activity of which id documented in the degradation of exudate protein in ring-shaped areas centered around the neutrophils(halo effect). Such halo formation can also be detected around certain large mononuclear cells, as well as around very small particles - which may represent thrombocytes. Application of trypsin inhibitors and various antirheumatic agents causes concentration-dependent inhibition of halo formation.