Demonstration of HLA and ABH antigens in fresh and frozen human menisci by immunohistochemistry.

The expression of HLA and ABH antigens in fresh, frozen, and twice-frozen normal human meniscal tissue was evaluated with use of immunohistochemistry. A generalized expression of Class-I and Class-II HLA antigens was found in the endothelial and synovial cells of all three forms of tissue. Fibrochondrocytes were Class-I positive and Class-II negative. ABH antigens were expressed by endothelial cells in relationship to the blood group of the patient. Freezing preserved most of the HLA and ABH molecular structure. Although the normal meniscus consists of a relatively few chondrocytes embedded in an extracellular matrix, it also contains Class-II and ABH-positive endothelial cells and Class-II-positive synovial cells. These antigens are present at the moment of transplantation and could evoke an immune response in the host that would modulate the results of meniscal allografting.