Abstract
A severe and frequently fatal graft-versus-host (GVH) reaction may result from the administration of allogeneic immunologically competent lymphoid cells to a host deficient in cell-mediated immunity (1, 2). High speed centrifugation, freeze thawing, and radiation have been used to free the blood or blood products of immunocompetent cells prior to their administration to patients. The capacity of lymphocytes to respond to phytohemagglutinin (PHA) and incorporate radiolabeled thymidine following irradiation has been used to measure the amount of immuno-competence remaining (3, 4). From certain of these studies (3), it has been maintained that even large doses of irradiation do not inhibit immunocompetent cells as revealed by the capacity of those cells to respond by in vitro transformation to PHA. This evidence has been taken as a warning that irradiation in vitro may not be a reliable method of eliminating the hazard of GVH reactions. Coifman et al. (5) have recently shown that this in vitro analysis of lymphocyte function following irradiation may not be a valid assessment of immunocompetence. The following experiments were designed to reassess the effects of irradiation on a well-defined biological function of immunocompetent cells using an in vivo GVH assay.
This study demonstrated that in vitro irradiation, under optimum conditions of oxygenation and cell numbers, can effectively inhibit a sufficient proportion of immunocompetent cells to keep the hazard of GVH reactions to a minimum. It is clear, however, from the results reported herein, that, when assayed by this function like so many others, irradiation in moderate doses may leave a residue of cells capable of initiating a GVH reaction.
Methods. Inbred mice of C3Hf/Bi (these mice will be referred to as C3H in the text) and A/jax and their F1 hybrids of these strains were used.
Get full access to this article
View all access options for this article.