Distribution of lysozyme in synovial tissue of patients with osteoarthritis and rheumatoid arthritis demonstrated by different enzyme histochemical methods

Cutaneous mucinous nodule in a patient with rheumatoid arthritis

We report a cutaneous mucinous nodule on the inflamed elbow joint in a patient with rheumatoid arthritis (RA). The lesion is clinically characterized by a continuous flow of mucinous exudates from the nodule, and histologically by an extensive mucin deposition and proliferations of the fibroblastic cells and mononuclear cells. The histological findings suggest the histogenesis of this unique nodule is related to extralesional proliferation of synovial lining cells consisting of monocyte-macrophage lineage cells and fibroblast-like cells which potentially produce synovial fluid. Four patients have been hitherto reported in the published work and all of them have been associated with RA. The condition may be one of the characteristic skin manifestations of RA.

An immunohistochemical study of the distribution of biotin in tissues of pigs and chickens

An optimised indirect peroxidase-anti-peroxidase immunohistochemical technique was used to detect endogenous biotin in frozen tissue sections from biotin-supplemented and biotin-depleted pigs and chickens. A monoclonal anti-biotin antibody was used as primary antibody in this technique. Immunoreactive biotin was detected in many tissues of both species including liver, kidney, pancreas, adipose tissue, adrenal gland, testis, brain, choroid plexus, cardiac and skeletal muscle, epithelium of the respiratory and digestive systems, skin and lymphoid tissues. The specificity of immunostaining for biotin was confirmed by the finding of reduced staining intensities in tissues of biotin-depleted animals compared to those of biotin-supplemented animals. The results of this study suggest that biotin has metabolic functions in a wider range of tissues than previously known. They also indicate that endogenous tissue biotin should be considered as a source of false-positive staining when immunohistochemical or histochemical techniques which use avidin or streptavidin reagents or anti-biotin antibodies as components of the detection system, are applied to tissue sections.

The neo-synovial membrane of patients with active rheumatoid arthritis at resynovectomy. Histomorphological and immunohistological evaluations

Neo-synovial membranes, which formed after "primary" synovectomy in 21 patients with rheumatoid arthritis (RA), were studied at resynovectomy. The clinical, histomorphological, and immunohistological data were compared with data derived from "primary" synovial membranes from RA and osteoarthritis (OA) patients. The clinical data suggest a less active rheumatoid inflammatory response after synovectomy. Histomorphologicaly, the synovitis in resynovectomized neosynovial membranes of RA revealed no qualitative differences when compared with synovitis in the "primary" synovium. However, the degree of the inflammatory rection evaluated by the different parameters was found to be distinctly lower. The immunohistological data correlated with these findings.

Localisation of lysozyme mRNA in rheumatoid synovial membrane by in situ hybridisation

Type A synovial lining cells have been shown to contain lysozyme in their lysosomes. This might be phagocytosed because synovial fluid contains lysozyme originating from tissue macrophages and articular cartilage but in arthritides, in particular, from neutrophils. In situ hybridisation with 35S labelled cDNA was used to detect mRNA for lysozyme over synovial lining in patients with rheumatoid arthritis. No hybridisation was found with lactoferrin cDNA, which was used as a negative control. Computer search against the EMBL gene bank (release 14) did not show any significant cross hybridisation to a known sequence. In cytological specimens 35S-cDNA:mRNA hybrids were observed in positive but not in negative control cells. The presence of lysozyme and its mRNA suggests that type A synovial lining cells are of mononuclear phagocyte lineage.

Ultrastructural localisation of muramidase in the human synovial membrane

The synovial intimal cell layer comprises two morphological types of cell, A and B, with an intermediate type also postulated. Type A cells show features in common with other cells of the mononuclear phagocyte system, while type B cells appear similar to fibroblasts and are assumed to have synthetic activity. Muramidase is a marker of mononuclear phagocytic cells, and we have investigated the synovial membrane for the presence of this enzyme in cells by an immunogold labelling technique. Muramidase was localised within intracytoplasmic vacuoles in subintimal macrophages and type A synoviocytes. This finding provides further evidence that type A cells are closely related to macrophages.

T-lymphocyte subsets and HLA-DR-expressing cells in the osteoarthritic synovialis

Rheumatoid and osteoarthritic synovial membranes biopsied at operations were analysed in frozen sections with an immunohistochemical monoclonal antibody technique. It is evident from this investigation that immunocompetent inflammatory cells such as HLA-DR-expressing non-T cells and T cells in general occur even in the osteoarthritic synovial membrane, though to a lesser degree than in rheumatoid arthritis. In about half of the osteoarthritic synovial membranes these T cells were clustered in follicle-like formations. In both diseases, most of the T cells were helper/inducer T cells whereas cytotoxic/suppressor T cells occur sparsely and almost exclusively in rheumatoid arthritis.

Analysis of mast cells in rheumatoid arthritis and osteoarthritis by an avidin-peroxidase staining

As demonstrated by labeling with peroxidase, avidin was found to bind selectively and distinctly to mast cell granules. Inhibition studies suggested that avidin is bound by heparin. Based on this new mast cell staining procedure, mast cell distribution in the inflamed synovium of rheumatoid arthritis (RA) and osteoarthritis (OA) has been investigated. In the subsynovial layer, a significant decrease in mast cell numbers was observed in RA-synovium when compared with OA-synovium. This decrease correlated with the presence of lining cell ulcers and granulation tissue and can be interpreted as the result of mast cell degranuation induced by complement-mediated or immune complex-triggered mechanisms.