The Role of Soft Connective Tissue in the Breakdown of Pig Articular Cartilage Cultivated in the Presence of Complement-Sufficient Antiserum to Pig Erythrocytes
1. The penetration and interaction of IgG of normal heat-inactivated rabbit serum (NRS), and of rabbit antiserum to pig erythrocytes (A-S) without (A-S + NRS) and with complement (A-S + C′), have been studied in organ cultures of pig articular cartilage by immunohistochemical methods. 2. In explants of metacarpal condylar cartilage cut above the level of the invading marrow (invasion zone), IgG of NRS, A-S + NRS and A-S + C′ did not penetrate beyond the most superficial layers of the articular chondrocytes; the reaction was more intense after treatment with A-S, especially in the presence of C′. 3. In similar explants cut at a deeper level to include part of the invasion zone, IgG of NRS entered the invasion cavities in the cartilage and penetrated a short distance into the overlying matrix. After exposure to A-S + C′, the invading marrow reacted intensely, and IgG often penetrated far into the cartilage where the matrix was depleted (see Part I); cellular staining was restricted to the surfaces of viable chondrocytes but was intense throughout dead cells. 4. Fibrous cartilage from the junction between the condylar cartilage and the periosteum and periosteal bone, was very permeable to IgG of NRS, A-S + NRS and A-S + C′. In explants treated with A-S, many cells reacted for IgG; the intensity of the response was increased by the presence of C′. 5. When condylar cartilage without the invasion zone was grown in contact with fragments of joint capsule (affronted explants), IgG of NRS and A-S entered the area of depleted matrix near the capsular explant (see Part I) and reacted with the chondrocytes; penetration and cellular reaction were greater after exposure to both A-S and C′.