Physiological and pathophysiological aspects of the immune system contributing to a biomathematical model of lymphocytes.

The effects of chronic low-dose irradiation on the immune system and the lymphocytes are largely unknown. The uranium miners in the former German Democratic Republic (GDR) were exposed mainly to a local low-dose irradiation in the lung by radon and its progeny, but also to some whole-body gamma irradiation. The local irradiation led to an increased rate of lung cancer and perhaps to some increase in extrapulmonary neoplasms. But little is known about the effects on the lymphocytes circulating and recirculating to the lung. As a prerequisite for the establishment of a biomathematical model to estimate lymphocyte fluxes, and to assess the radiation effects on the lymphocytic (and stem cell) populations passing through the lung, it was necessary to establish the current knowledge with respect to the physiology and pathophysiology of the lymphocytic cell renewal systems. The data concerning lymphopoiesis and lymphocyte kinetics, which are important for the development of this model, are summarized. The distribution of lymphocytes between different compartments including the lung is taken into consideration, as well as the effects of acute and chronic irradiation on the immune system. The extracorporeal irradiation of the blood (ECIB) may serve as a model of irradiation of blood in the lung. This review shows that many data necessary for development of a detailed biomathematical model are still missing, especially data concerning details on lymphocyte production rates of their different subsets and regulatory mechanisms of the lymphocytic system.