Effect of 500 r Whole Body Irradiation on the Cellular Composition of the Peritoneal Fluid Following an Intraperitoneal Injection of Antigen in Mice

Summary The effect of 500 r whole body irradiation on the cellular composition of peritoneal fluid prior to and following an intraperitoneal injection of fluid tetanus toxoid was studied. It was noted that: Irradiation given prior to antigen injection greatly reduced the number of eosinophil and mononuclear cells in the peritoneal fluid and prevented the increase of these cells in response to the antigen in both immunized and nonimmunized mice. The inhibitory effect was marked for 14 days and was still evident on the 42nd day after irradiation.Irradiation given at various times after the antigen injection also reduced the concentration of mononuclear cells in the peritoneal fluid and consistently inhibited the mononuclear response to the antigen injection in both immunized and nonimmunized mice.Irradiation given after the antigen injection varied in its effect upon the concentration of eosinophil cells depending upon the immunity of the animal to the toxoid and the time of irradiation relative to the injection. In nonimmunized animals irradiation had an inhibitory effect on the number of eosinophils. In immunized animals, irradiation 24 or 72 hr after the challenging injection did not inhibit the 4-day eosinophil response, and in some animals an increased concentration of eosinophils occurred. By the 7th day there was a significant decrease in the concentration of eosinophils as compared to the nonirradiated mice.The relation of mononuclear and eosinophil cells to immune responses was discussed. It was noted that there did not appear to be a correlation between the effects of irradiation on the mononuclear cell response and the ability of the animal to produce antitoxins. On the other hand there did appear to be a correlation between the effects of irradiation on the eosinophil response and on the ability of the mice to produce antitoxins. It was suggested that eosinophils are part of the antibody forming mechanism and may form the enzymatic template which is phagocytized and utilized by the mononuclear cells to form antibody.