STUDIES IN THE TRANSPLANTATION OF BONE III. The Immune Responses of Lymph Nodes Draining Components of Fresh Homologous Cancellous Bone and Homologous Bone Treated by Different Methods

The iso-antigens of homografts which evoke immune responses in their hosts possibly exist in two forms, namely, as H-antigens and as T-antigens (Medawar 1959a). The H-antigens, which include the blood-group substances (which are amino-acid polysaccharide complexes), can be identified by their capacity to provoke the formation of humoral (or serum) antibodies. H-antigens are widely distributed in the tissues and are relatively stable to heating and freezedrying. The T-antigens evoke the production of cell-bound antibodies and can be identified by their capacity to elicit transplantation immunity. Billingham, Brent and Medawar (l956a) first showed that the antigens responsible for transplantation immunity in mice were DNAprotein complexes residing in the nuclei of cells and probably in the chromosomal matter. More recent work has suggested that the immunologically determinant groups of both the Hand the T-antigens are identical, but that the T-form has some extra attachment, perhaps a lipid or a lipoprotein, which excites a predominantly cellular response (Kandutsch and Reinert-Wenck 1957; Billingham, Brent and Medawar 1958; Medawar 1960). T-antigens are relatively unstable, being destroyed by heating, freezing and thawing, and freeze-drying. There is evidence to suggest that the instruments of transplantation immunity are not the serum antibodies but the antibodies bound to cells of the lymphoid series (Medawar 1959b). Examination of the sera of animals which had received transplants of fresh homologous bone tissue has failed, in all recorded instances, to demonstrate serum antibodies which could be considered indisputably to result from antigens within bone tissue itself (Bonfiglio, Jeter and Smith 1955; Curtiss and Herndon 1955, 1956; Sherk 1960; Burwell and Gowland l96la). However, after the transplantation offresh homologous cancellous bone into subcutaneous sites in rabbits, characteristic immune responses occur in the regional lymph nodes (Burwell 1960a, Burwell and Gowland l96lb). Histological examination of the lymph nodes, removed at different time intervals after the insertion of fresh homologous iliac bone into their drainage areas, revealed great accumulations of large and medium lymphoid cells in the cortices and the medullae of the nodes; the cells increased in number to a maximum at five days after the insertion of the cancellous bone homografts into the drainage areas of the nodes and returned to normal at about the fourteenth day. Large and medium lymphoid cells are thought to produce intracellular antibodies to tissue grafts. In this communication we report the effects of subcutaneous transplants of components of fresh homologous cancellous bone, and implants of marrow-containing homologous cancellous bone treated by physical or chelnical methods, upon the large and medium lymphoid cell content of the regional lymph nodes. The reactions of the lymph nodes to the homografts are used as histological indicators of the antigenicity of the various grafts. The principal antigenic fraction of fresh homologous iliac cancellous bone is found to lie in the nucleated cells ofthe red bone marrow. Homologous cancellous bone devoid of marrow does not usually elicit immune responses in the regional lymph nodes unless new homograft bone formation occurs. In addition most physical and chemical methods of treatment of homologous cancellous bone grafts reduce their ability to evoke immune responses in the regional lymph nodes. A preliminary report of this work has been published (Burwell l960b)