Lysozyme in the labial salivary glands of patients with rheumatoid arthritis

Lysozyme (muramidase) levels in the saliva have previously been discovered to be elevated in patients with rheumatoid arthritis (RA), a fact which has been tentatively ascribed to immunological reactivity in the salivary glands due to RA. To characterize further the mechanisms involved in elevation of salivary lysozyme, labial salivary glands from 57 RA patients and from 43 healthy control (CO) subjects were assessed morphologically, using ANAE (acid alpha-naphthyl acetate esterase) stain for B, T and MPS cells, as well as by immunoperoxidase kits for lysozyme. In addition, lysozyme concentration in serum, saliva and lacrimal fluid was chemically determined. Lysozyme immunoreactivity was disclosed in the serous acinar cells and in the epithelium of intercalated ducts, but never in the striated ducts. No difference in the localization or intensity of the staining could be found between RA and CO series. Lysozyme levels were elevated in serum and in saliva, but not in lacrimal fluid of RA patients. The percentile distribution on B, T, and MPS cells was equal in both series. MPS cells, which are known to be a rich source of lysozyme, were fewer in glands showing lysozyme immunoreactivity than in lysozyme-negative glands. This is evidence against the suggested direct relationship between MPS cell counts and lysozyme concentrations in external secretions. The results are discussed in terms of the immunological reactivity in salivary glands of patients affected by RA, with special emphasis on the intimate co-operation of the different protective systems (IgA, beta 2-microglobulin, lactoferrin, and lysozyme) shown to be operative in such glands.(ABSTRACT TRUNCATED AT 250 WORDS)