Absence of immunoglobulins in rheumatoid cartilage‐pannus junctions

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Abstract
Immune complexes (1C) present in the superficial region of rheumatoid articular cartilage may be an important factor in the invasion of the cartilage by pan-nus. The presence of such 1C at the cartilage-pannus junction in rheumatoid articular cartilage invaded by pannus was investigated by using hnmunoelectron microscopy with horseradish peroxidase anti-human im-munoglobulin (Ig). It was observed that, although the pannus-free surface of the cartilage contained easily detectable deposits of Ig, the areas covered by pannus failed to show any Ig in the 5 patients studied. This was true even in areas immediately adjacent to the advancing edge of the pannus which presumably had only recently been invaded by the granulation tissue. These results were confirmed by fluorescent antibody ultraviolet microscopy. It was concluded that rheumatoid pannus invasion of the free cartilage surface containing trapped 1C results in the disappearance of such complexes.