Using the technique of two-dimensional (2D) electrophoresis with consecutive silver staining, we investigated samples of serum, synovial fluid and synovial tissue obtained from 19 patients suffering from rheumatoid arthritis (RA) or non-RA arthritis. From these experiments we have drawn the following conclusions. 2D electrophoresis of serum, synovial fluid and synovial tissue extracts taken from patients suffering from joint diseases is a reproducible method. Repeated runs of the same sample reveal an essentially constant protein spot pattern. The time period between surgery and tissue preparation did not influence the number of protein spots when less than 15 h was involved. The protein spot number is always lower in synovial fluid than in either synovial tissue or serum in RA and non-RA patients. The mean value for the number of spots is 68 for the inflamed tissue irrespective of the cause of arthritis (RA and non-RA group taken together) and 47 for the control group. This difference is significant. We were able to definitely identify 7 spots in the tissue extract. We did not find RA-specific protein spots in either serum, synovial fluid or tissue extracts from the synovial membrane. The only significant difference between RA patients and either non-RA or control group patients concerning the protein spot pattern is the increased size of the immunoglobulin spot (mainly IgG) in RA. In addition, we discuss possible reasons for failure of the 2D electrophoresis technique to detect disease-specific protein patterns.

We describe an improvement of the immunogold technique, which is based on the colour development of silver-intensified immunogold signals. This method (referred to as the coloured-SIG technique) was found to be as sensitive as the silver-intensified immunogold method and more sensitive (in two of the three tested systems) than immunoenzymatic procedures, such as the peroxidase/antiperoxidase technique or the avidin-biotin system. The coloured SIG-method results in either a magenta-red or a cyan-blue final reaction product. Therefore, this new improvement of the immunogold technique should be useful in double-staining methods, immunoblot methods and conventional immunostaining methods.

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A two-dimensional electrophoresis technique for analysing sections of human tissue is described. Cryostat sections, 10 microns thick, are placed on an isoelectric focusing gel and then transferred to an SDS gel in the second dimension. The protein pattern is visualized by silver staining and is thought to represent soluble proteins. The silver-stained proteins were found to be both reproducible and, to the extent tested, organ-specific. This method was used to analyse 43 synovial membranes from patients suffering from rheumatoid arthritis or degenerative joint diseases. The analysis did not reveal any specific protein pattern for rheumatoid arthritis. The protein spot number was not related to the cause of arthritis. However, the total protein spot number was related to the histomorphological synovitis type, with those exhibiting either an exudative or proliferative synovitis pattern possessing significantly higher protein spot numbers than those specimens exhibiting a sero-fibrous or lympho-plasmacytic pattern of synovitis.

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