The Control of Cell Division During the Immune Response

Abstract

Following immunization with antigen a proliferative response was detected in both the bone marrow and spleen. Concomitant with this heightened proliferative activity there occurred a significant hypercalcaemia. The elevated proliferation was always associated with a hypercalcaemic episode regardless of the antigen chosen. Removal of the parathyroid glands causes severe hypocalcaemia and under these conditions the thymus becomes severely involuted and the bone marrow hypoplastic. No incremental increase in plasma calcium occurred a parathyroid rats following antigen nor was there any proliferative response in the bone marrow. A parathyroid rats rendered normocalciuric by feeding a high calcium/low phosphate diet likewise failed to show any proliferative response in the bone marrow following antigenic challenge. The proliferative response of splenic lymphocytes in response to antigen was largely unaffected by parathyroidectomy. The immune response of rats was impaired by parathyroidectomy. Primary antibody responses to heterologous erythrocytes were slightly lower than normal animals as were the numbers of haemolytic plaques which develop in the spleen. Parathyroidectomy potentiated the delayed-type hypersensitivity response to oxazolone, perhaps suggesting a selective deleterious effect on a suppressor-cell population. Splenic lymphocytes from parathyroidectomized animals were able to elicit a normal graft-versus-host reaction as assessed using a popliteal lymph node weight assay. It was also shown that a normal pool of memory cells was formed by parathyroid rats. However, reduced hyperplasia of when node occurred when the recipient rat was parathyroidectomies. In view of the differential effect which parathyroidectomy had on the proliferative response of the bone marrow and spleen, it seems likely that the target cells for parathyroid-mediated enhancement of proliferation are antigen-insensitive. It is postulated that parathyroid hormone may have a role in the replenishment of the lymphoid cell pool by stimulating increased division of more primitive lymphoid elements. The conclusion drawn from the research is that this method of measurement of changes in urban land use by means of aerial photography produces areal data of an accuracy, and in such a form, as to be suited to the purposes specified.