Studies in the Transplantation of Bone. Vi. Further Observations concerning the Antigenicity of Homologous Cortical and Cancellous Bone.

Recent studies have shown that the red marrow is the principal antigenic component of a fresh homograft of iliac bone and that iliac bone tissue washed free from marrow is not demonstrably antigenic (Burwell and Gowland 1962, Burwell 1963). These findings clearly emphasise the necessity, when investigating the antigenicity of fresh cortical and cancellous bone, of cleansing the homograft of red marrow before its insertion into the host. In several previous studies in which immunity was evoked by homografts of bone from which the marrow had not been so removed, it seems likely that the immunological effects observed resulted more from the marrow than from the bone tissue itself (Bonfiglio, Jeter and Smith 1955; Curtiss and Herndon 1955, 1956; Enneking 1957; Enneking, Gratch and Ethridge 1957; Urist, Macdonald and Jowsey 1958; Enneking and Gratch 1959; Chalmers 1959; Hancox, Owen and Singleton 1961). Likewise in the recent experiments of Ray and his colleagues (Sabet, Hidvegi and Ray 1961 ; Chalmers and Ray 1962) in which embryonic femora were transplanted as homografts into adult mice, it is not possible to apportion the transplantation antigenicity of their grafts to bone, to cartilage or to marrow. In the present studies the primary and secondary immune responses of regional lymph nodes have been used as histological indicators of the antigenicity of foreign cortical and cancellous bone grafts inserted into their drainage areas. Previous work has shown that the secondary response which occurs in lymph nodes draining second-set homografts of marrowcontaining iliac bone occurs more rapidly and is ofgreater magnitude than that ofthe primary response (Burwell 1962a, b). Hence it was considered that the insertion of bone homografts into the drainage areas of lymph nodes previously sensitised to donor tissue might reveal antigenicity which was not detected after the insertion of first-set homografts into the drainage areas of lymph nodes of non-sensitised animals (Burwell and Gowland 1962). The findings of the present work are related to previous knowledge ofbone immunology. It is concluded that: 1) fresh homologous cortical bone contains transplantation antigens; 2) fresh homologous cancellous bone has yet to be shown indisputably to contain such antigens: and 3) some methods of physical and chemical treatment of marrow-containing iliac bone permit tissue antigens in the marrow to remain immunologically active.