Immune complex mediated destruction of cartilage in antigen-induced arthritis of rabbits.

Antigen-induced arthritis of rabbits is used as a model to study pannus-free destruction of cartilage in rheumatoid arthritis (RA) by transmission and scanning electron microscopy, incorporating plain and immune labeling techniques. During the acute "arthus" phase of the RA, immune complexes form and persist in these tissues. We observed the progressive formation of electron dense material rich in immune complexes within a millimicron of the hyaline cartilage surfaces that preceded erosion and loss of surface tissue. Polymorphonuclear neutrophils congregated at the cartilage margins to engulf immune complexes at and within the cartilage surfaces. The changes occurred in regions of hyaline and fibrocartilage free of pannus. Immune complex formation appeared to be a central feature of the cartilage destructive changes, and may be central to mechanisms of tissue loss and similar to those observed in RA.