Abstract
1. The response of the first regional lymph node to a homograft of fresh iliac cancellous bone inserted subcutaneously into the rabbit's ear three weeks after the introduction of a similar graft from the same donor into the same ear has been investigated in thirty rabbits. Fifteen rabbits which received second-set autografts of cancellous bone have also been studied.
2. The insertion of second-set homografts of fresh marrow-containing cancellous bone evokes an immune secondary response in the lymph nodes draining the grafts.
3. The increase in weight of the first regional lymph nodes on the side receiving second-set homografts is more rapid and of greater magnitude than that of nodes draining first-set homografts of cancellous bone. Second-set autografts evoke weight changes in the draining nodes similar to those in nodes draining first-set autografts of cancellous bone.
4. The histological changes which occur in the lymph nodes draining the second-set homografts (secondary response) are described and compared with those occurring in lymph nodes draining first-set homografts of cancellous bone (primary response).
5. In the primary response the distribution of large and medium lymphoid cells is throughout an activated sector of the cortex of the lymph node (Burwell and Gowland 1961), but in the secondary response these cells are found peripherally within the activated sector of the node. In both the primary and the secondary responses large and medium lymphoid cells are found in the medullary trabeculae of the lymph nodes.
6. The differences between the primary response of lymph nodes draining a tissue homograft (cancellous bone) and the primary response of lymph nodes draining classical antigens, and reported by other workers, are described.
7. Knowledge concerning the inflammatory response in the tissues of the host surrounding homografts of fresh cortical and cancellous bone implanted into animals previously sensitised to tissue from the respective donor is reviewed.
8. The late phase of new bone formation by homografts of fresh cancellous bone is discussed in the light of immunological studies.
