The presence and possible significance of C-reactive protein in rheumatoid inflammation.

C-reactive protein (CRP) is capable of binding to a variety of ligands with subsequent complement fixation in vitro. By this means CRP may contribute to the inflammatory process in some diseases. Elevated levels of CRP were demonstrated in synovial fluids (SF) from patients with a variety of inflammatory arthritides. The contribution of CRP to inflammation in SF was investigated. Sera and SF from patients with rheumatoid and other forms of arthritis were examined for the presence of ligand bound CRP. We were unable to demonstrate significant amounts of bound CRP, either as increased molecular weight using gel filtration, or in the form of CRP-ligand-immunoglobulin complexes using a modified enzyme linked immunosorbent assay. CRP was found associated with the pellet after centrifugation of SF samples. Preliminary studies showed CRP detectable on the surface of cells in some inflammatory SF. The presence of this cell associated CRP suggests that ligand bound CRP may not be demonstrable in the sera and SF examined due to interaction with cells.