The permeability of the synovial membrane for proteins is larger in rheumatoid arthritis than in osteoarthrosis, in rheumatoid arthritis with high CRP activity larger than in rheumatoid arthritis with low CRP activity. 2. The diffusion by the synovial membrane in most plasma proteins takes place depending on their molecular weight. Of the 14 proteins tested only haptoglobin and fibrinogen did not follow this regularity. 3. While the non-immune proteins proved in the synovial fluid only come from the blood plasma, the immune globulins IgG, IgA, and IgM as well as lysozyme are partly also locally synthetized and enriched in rheumatoid arthritis. In rheumatoid arthritis lysozyme is present in the synovia not only in free, but in most cases also in cell-bound form.
