Immunopathological study on human cartilage allografts.
The fate of human cartilage allografts and the mechanism of its kinetical development were studied histopathologically and immunohistologically. After transplantation, the grafts underwent necrosis, calcification and were partially invaded by osteoplastic tissue of the host and eventually replaced by bone tissue. Thus, the contour of the transplanted cartilage was kept partially by the living cartilage and the newly-formed osseous tissue. The grafts were surrounded initially by granular tissue and then by scar tissue, in which numerous T cells and a few macrophage infiltrates were noted. In T cells, T4+ lymphocytes predominated but T8+ cells accounted for a small number. B cells were not found within the infiltrates. Most of the infiltrating cells expressed 12 antigens, indicating that the majority of T cells were activated. It was concluded that T lymphocytes mediated cellular immunity played an important role. The chondrocytes of the cartilage did not express HLA I and II antigens before transplantation, but one month later, the living chondrocytes became HLA I and II antigens positive, and the antigen expression became stronger with the elapse of time; this might be induced by lymphokins, especially by interferon produced by the infiltrating lymphocytes. Such an expression of MHC antigens on chondrocytes might contribute to the further enhancement of immunorejection.