EXTRACORPOREAL IRRADIATION OF BLOOD AND LYMPH IN ANIMALS: ITS EFFECT ON HOMOGRAFTS AND ON LYMPHOMA

A controlled clinical trial of the immunosuppressive effect of extracorporeal irradiation of the blood in renal allotransplantation

The immunosuppressive effect of extracorporeal irradiation of the blood (ECIB) in renal allotransplantation (RAT) has been investigated in a controlled clinical trial. A series of 101 uremic patients undergoing intermittent hemodialysis in preparation for RAT were allocated randomly to two groups; a treated group +ECIB (n=55), and a control group 0-ECIB (n= 46). ECIB treatment was given in the form of a fixed dose, with a transit dose of 400 rad and a cumulative dose of approximately 50 000 rad, both before and after RAT. A selective long-term lymphocytopenia was usually obtained, with no effect on immunoglobulins, complements or plasma proteins. Erythrocyte count was reduced in the majority of cases, but this had no limiting effect on the implementation of treatment. The shortest survival times and most deaths occurred in the +ECIB group. The first rejection episode occurred later in the +ECIB group, but there was no difference between the groups in the number of rejections during the first two months or during the whole observation period. There were more cases with two or more rejection episodes in the +ECIB than in the 0-ECIB group. There was no difference in graft survival, but shortest patient survival and most deaths after RAT occurred in the +ECIB group. It must therefore be concluded that the immunosuppressive effect of ECIB has no practical clinical relevance in RAT, and that ECIB given in the manner described involves the possibility of side-effects so serious that the method cannot be recommended.

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.

Fractionated total lymphoid irradiation as preparative immunosuppression in high risk renal transplantation: clinical and immunological studies

Twenty-two patients at high risk to reject renal allografts have been treated with fractionated total lymphoid irradiation (FTLI) prior to transplantation of primary (2), secondary (16) or teritary (4) renal allografts. All patients undergoing retransplantation had rapidly rejected previous grafts. At 24 months following transplantation, 72% of grafts were functioning in the TLI group compared with a 38% graft function in an historical control group of recipients receiving secondary or tertiary grafts and treated with conventional immunosuppression. Important variables in determining success of transplantation following fractionated TLI include the dose of TLI, the interval from radiation to transplantation, and maintenance, post-transplant immunosuppressive therapy. Optimal results were achieved with 2500 rads delivered in 100 rad fractions followed by transplantation within two weeks, and a tapering prednisone schedule and maintenance azathioprine post-transplantation. Seventeen patients had significant complications of the radiation treatment and there was one death, prior to transplantation, associated with pneumonitis. In vitro assessment of immune function demonstrated marked peripheral T cell depletion and loss of in vitro responsiveness to mitogen and allogeneic stimulation following FTLI. The administration of donor bone marrow at the time of transplantation did not produce chimerism. The results suggest that when properly utilized FTLI can produce effective adjunctive immunosuppression for clinical transplantation.

Long-term survival of skin allografts in mice treated with fractionated total lymphoid irradiation

Treatment of recipient Balb/c mice with fractionated, high-dose total lymphoid irradiation, a procedure commonly used in the therapy of human malignant lymphomas, resulted in fivefold prolongation of the survival of C57BL/Ka skin allografts despite major histocompatibility differences between the strains (H-2d and H-2b, respectively). Infusion of 10(7) (C57BL/Ka x Balb/c)F1 bone marrow cells after total lymphoid irradiation further prolonged C57BL/Ka skin graft survival to more than 120 days. Total lymphoid irradiation may eventually prove useful in clinical organ transplantation.