Prevention of Radioleukaemia by Lymph Node Shielding

Abstract

IN mice subjected to a schedule of irradiation normally producing a high yield of leukaemia of the thymic lymphoma type, it has been shown that the administration of foetal haemopoietic tissue leads to the presence of dividing cells (which have the chromosome characteristics of the donor almost exclusively) in the target organs of the hosts¹. A related finding is a significant drop in the mortality from leukaemia. Kaplan has attributed the phenomenon of a lowered incidence of radioleukaemia resulting from the intravenous administration of bone marrow to a bone marrow factor². It has been thought, as a more recent alternative, that inhibition of radioleukaemia follows repopulation of haemopoietic tissues and thymus by unirradiated donor cells³. The incidence of the leukaemia induced by radiation which appears to have its origin within the thymus is paradoxically unaltered by the intravenous administration of lymph node material in dissociated form. Other cells intimately associated with the lymph node but difficult to dissociate from its structure may have been excluded in the preparation of such lymph node inocula. Because of this exclusion, and because feedback mechanisms may implicate the endothelial cells of the post-capillary vessels in lymph nodes and perhaps littoral cells⁴, the place of whole lymph node in situ in altering the pattern of leukaemia induction was tested.