Graded dosages of x-irradiation from 500r to 3000r inhibited destruction of Diemictylus viridescens allografts at 23 k 0.5"C for at least as long as the survival time of the hosts (up to 35 days). Lymphocytes were observed in 20% of the grafts whose hosts received 500r and lOOOr but they were present in far weaker concentrations than seen in any control grafts at all stages of rejection. No lymphocytes were evident in any grafts on hosts irradiated with 1500r, 2000r, and 3000r.The effects of various temperatures on allograft rejection in the newt were also examined. There was no difference in the mean survival times of grafts maintained at 3OoC and 23°C. At 2OoC, however, hemostasis and hemorrhaging were significantly delayed by a factor of 1.6 and 1.7 times, respectively, when compared with the findings at 23OC. At lO-l5"C, no hemostasis or hemorrhaging were displayed for 191 days after transplantation. Lymphocytes, however, were apparent in very low concentrations in the tissues of some of the grafts and localized destruction of a few melanophores were noted. Two grafts maintained at l0-15"C for 155 days and then transferred to 2OoC were completely destroyed within 36 days. This destruction was more rapid than for grafts initially maintained at 20'C.The immunologic rejection of skin allografts in the adult newt, Diemictylus viridescens, is marked by a chronic infiltration of small lymphocytes during the third and fourth weeks following transplantation. Concomitant with this lymphocytic infiltration are a series of externally observable events which include in their proper chronology: secondary vasodilation, hemostasis, hemorrhaging, and melanophore degeneration (Cohen, '66b).The third paper in this series extends the existing information on tissue transplantation immunity in the newt by exploring the effects of x-irradiation and temperature on skin allograft rejection.X-irradiation of mammalian and avian hosts prior to skin grafting has been responsible for delaying or inhibiting allograft rejection (Dempster et al., '50; Main and Prehn, '57; Toolan, '51a). Cooper ('64) reported that x-irradiation of FunduZus delayed scale allograft rejection for several days, the delay being dependent on the dosage used. To confirm and extend information concerning the effect of irradiation on skin allograft survival in lower J. ExP. ZOOL,., 163: 231-240.vertebrates, adult D. viridescens were first irradiated with several different dosages of x-rays and then skin grafted.The immune response of diverse poikilothermic species to tissue allografts and to soluble and particulate antigens is strikingly affected by the ambient temperature; the lower the temperature the more delayed is graft rejection (Hildemann and Cooper, '64; Simnett, '65) or the lower the titer of antibodies elicited (Elek et al., '62; Evans, '64; Krueger and Twedt, '63).In the present study, the effects of 10-15"C, 20°C, and 30°C on allograft rejection were studied in Diemictylus and the results compared with skin graft rejection at 23"C, the temperat...
