Abstract
1. The effects of the insertion of pieces of fresh cancellous bone into the subcutaneous tissues of the ear upon lymph nodes and spleens have been investigated in seventy rabbits.
2. The main immunological response is found to occur in the first regional nodes draining the sites of insertion of homografts of bone, which show a considerable increase in weight compared with nodes draining autografts of bone.
3. An increased number of large and medium lymphoid cells occurs principally in the first regional node of the homografted animals, as Scothorne and McGregor (1955) observed using skin as the homografted tissue.
4. The large and medium lymphoid cell response is found in both the cortex and the medulla of the lymph nodes. In the cortex a sectoral distribution of the cellular response is observed and the name reactive cortex is given to these sectors. Evidence is presented to show that the sectoral pattern of reactivity is probably determined by the localised entry into the node of iso-antigens through lymphatic vessels draining the bed of the graft.
5. We have made a quantitative analysis of the large and medium lymphoid cell response in the reactive parts of the diffuse lymphoid tissue of the cortex. The mean maximal large and medium lymphoid cell response occurs five days after the insertion of bone homografts.
6. The origin and fate of the large and medium lymphoid cells and their role in the production of antibodies is reviewed in the light of recent work.
7. A correlation is made between the maximal production of large and medium lymphoid cells in the first regional lymph node, the invasion of the graft bed with small lymphocytes and the inhibition of new bone formation in the homografts.
