Interaction of macrophages with rheumatoid articular cartilage.

These experiments investigated the in vitro interaction of macrophages and rheumatoid articular cartilage. When rheumatoid articular cartilage samples were incubated with normal peripheral blood mononuclear cells (PBM) for 1 hour or 12 hours in vitro, there were large numbers of PBM attached to the articular surface, and some PBM invaded the cartilage during the 12 hour incubation period. Conversely, in cartilage from osteoarthritic and normal subjects in the control, only a few PBM were attached to the articular surface after incubation with PBM. Under electron microscopic observation, macrophages were tightly attached to the surface and within the eroded cartilage. Light and electron microscopic observation with immuno-peroxidase staining of the rheumatoid cartilage surfaces showed the deposition of immunoglublins adjacent to the attached macrophages, suggesting the presence of immune-complexes as chemoattractants. These results suggest that macrophages in a rheumatoid joint may play an important role in the formation of pannus, resulting in the destruction of cartilage to interact with immune-complexes trapped in the superficial region of the rheumatoid articular cartilage.