Immunodeficiency in RFM/(T6xRFM)F1 mouse chimaeras with lethal host-versus-graft syndrome.

Rather than central tolerance, the perinatal inoculation of related F1 hybrid spleen cells into inbred mice may result in host-versus-graft (HVG) reactions manifested as transient autoimmunity, or as a lethal immunodeficiency syndrome. RFM/(T6xRFM)F1 chimaeras with lethal disease die in 30 days with lymphosplenomegaly, immune complexes and impaired immune responses. The present studies used in vitro proliferation assays to show that the HVG reaction caused hyperplasia sufficient to account for the lymphosplenomegaly, while also causing severe impairment of splenic and nodal cell responses to concanavalin A (Con A) and to bacterial lipopolysaccharide (LPS). By 25 days, HVG mice could not distinguish between self and non-self as judged by mixed lymphocyte reactions (MLR) to RFM, (T6xRFM)F1 and third party A/J cells. There were no indications that host cells reactive to F1 donor cells had undergone clonal deletion, anergy or expansion. Flow cytometry revealed that donor T lymphocytes achieved stable engraftment, mostly in the nodes, despite the HVG reaction. Taken together with previous observations, these studies showed that HVG reactions in young parent F1/chimaeras can result in an immunodeficiency state which is characterized by an early appearing, profound and persistent impairment of both host and donor T and B cell functions. The results suggest that HVG reactions can contribute directly to immune deficits seen after clinical allogeneic bone marrow transplantation.

Effect of MR imaging on spleen colony formation following gamma irradiation.

This article describes experiments performed to examine the possible effect of interaction between ionizing radiation and magnetic resonance (MR) on damage to normal tissue. Eight-week-old ICR male mice were irradiated (cobalt-60 radiation) with 5, 6, or 7 Gy given either alone or followed by MR imaging. Other groups received fractionated doses of 6 Gy (3 Gy + 3 Gy) or 7 Gy (3 Gy + 4 Gy) either with or without subsequent MR imaging. Ten days after exposure, spleens were assayed for endogenous spleen colonies. The number of spleen colonies was lower at higher radiation doses, and fractionation of the dose resulted in an increase in colony number compared with a comparable dose in a single exposure. No difference was seen, however, between comparable radiation groups that were or were not subjected to MR imaging. In addition to the spleen colony assay, body weights and wet weights for spleen, thymus, and testes were obtained, since these suffer weight loss in proportion to radiation dose. As with the spleen colony assay, no significant effect of MR imaging was observed. These results indicate that for the normal tissues studied, MR imaging neither increases radiation damage nor inhibits repair between fractions.

Mechanisms of neovascularization. Vascular sprouting can occur without proliferation of endothelial cells.

The kinetics of endothelial cells during microvascular growth were studied using a model of inflammation-induced neovascularization of the rat cornea. Inflammation was produced by central silver nitrate cauterization, cellular proliferation was assessed by tritiated-thymidine autoradiography and nuclear counts on plastic sections, and formation of new vessels was studied on whole-mount preparations after vascular perfusion with colloidal carbon. The 3H-thymidine-labeling index of endothelial cells was significantly higher than normal at 1 day following cauterization, although neither mitotic figures nor vascular sprouts were present. The labeling index reached a peak at 2 days, when cell division was evidenced by mitotic figures and doubling of the number of nuclei per section. Actual vascular sprouting also began during the 1- to 2-day interval. To determine whether vascular sprouting was dependent upon endothelial cell division, proliferation was suppressed by X-irradiation (2000 or 8000 rads) prior to cauterization. In irradiated corneas displaying no cellular proliferation, vascular sprouting at 2 days was similar to that in contralateral shielded corneas. Vascular growth continued in irradiated corneas between 2 and 4 days, but at 4 days the length of the vascular ingrowth was reduced to 66.7 and 53.4% of control after 2000 and 8000 rads, respectively. Vascular ingrowth did not progress between 4 and 7 days. This study demonstrates that initial vascular sprouting does not require proliferation of endothelial cells, although under ordinary circumstances DNA synthesis has been stimulated and is in progress at the time of sprouting. After initial sprouting without proliferation, limited vascular growth can continue for about 2 more days but subsequently ceases. Ultrastructural evaluation suggested that migration and redistribution of existing endothelial cells from the limbal vessels enable vascular sprouting and elongation without cellular proliferation.

Expression of murine leukemia viruses in RFM mice with host versus graft disease after perinatal inoculation of (T6 X RFM)F1 lymphohemopoietic cells.

Host versus graft disease is the fatal syndrome of altered immunity that follows the perinatal inoculation of related F1 hybrid spleen cells to susceptible strains of inbred mice. The allogenic reaction results in severe depletion of T-lymphocytes, but causes hyperplasia and hypersecretion of B-cells. Among the long-term survivors of acute host versus graft reactions, there is a high incidence of nonthymic lymphomas associated with ecotropic murine leukemia virus that may be of donor F1 origin. The present studies were done to determine whether ecotropic murine leukemia virus played any role in the pathogenesis of acute host versus graft disease in RFM mice perinatally inoculated with (T6 X RFM)F1 spleen cells. In RFM/(T6 X RFM)F1 chimeras, N-tropic murine leukemia virus can be detected as early as 3 days. The progression of the disease was accompanied by increasing viral expression. The inoculation of N-tropic virus of F1 donor origin into RFM neonates failed to induce disease, although the virus proliferated. Detection of progressively rising titers of antibody to murine leukemia virus linked the virus to the development of hyperimmunoglobulinemia by virtue of its ability to serve as a replicating source of antigens. These and other studies provided evidence that the seemingly paradoxical appearance of hyperimmunoglobulinemia in T-cell-deficient mice with the host versus graft syndrome is due, at least in part, to the stimulation of presensitized F1 donor B-cells, which are not destroyed in the allogenic reaction, as are the T-cells. Another unusual finding was the detection of polytropic murine leukemia virus in 25-day-old RFM/(T6 X RFM)F1 chimeras. It is suggested that the allogenic host versus graft reaction favored the formation of recombinants.

Modification of radiation carcinogenesis by marihuana.

Male, female, and ovariectomized female Sprague-Dawley rats were irradiated with 400 rads, 150 rads, or 300 rads, respectively, of 60Co gamma rays when they were between 40 and 50 days of age. The animals were injected three times weekly with either marihuana extract or with alcohol-emulphor carrier. Comparable unirradiated groups were similarly injected. Mean survival time in males was significantly shorter in the 400 rad + marihuana group compared with the three other groups whose mean survival times did not differ. Through the 546 days that the males were observed, the total number of tumors other than fibrosarcomas was significantly greater following radiation and marihuana (22) than radiation alone (6). Fifteen of the tumors were of breast or endocrine tissues. No differences were seen in the unirradiated groups. In the females, which were observed for 635 days, the total number of breast tumors was greater with the combined treatment (38) compared with radiation alone (22). This was entirely due to a marked difference in the adenocarcinoma incidence, which was 21 (radiation + marihuana) compared with four (radiation alone). The number of adenofibromas was similar in the two groups. In the unirradiated female groups the breast adenocarcinoma incidence was eight in the marihuana group and two in the control group. Ovariectomy resulted in a lower breast tumor incidence in all groups. Nonbreast tumors were more frequent in the ovariectomized-irradiated groups. Radiation plus marihuana produced more nonbreast tumors (25) than radiation alone (17) in the ovariectomized females.

Radiation effects on pig skin. Exposure to different densities of ionization.

The effects on pig skin from radiations producing different densities of ionization have been determined. For the qualities of radiation employed, erythema was produced at a dose range from 1,240 to 3,440 rads and ulceration at 1,250 to 5,000 rads. In no instance did a radiation-induced neoplasm develop. In determining dose response, two of the most important physical parameters, associated with time of appearance and extent of lesions, were found to be the size of the area irradiated and the density of ionization of the radiations used. These data, on normal tissue tolerance, should be a value in future programs initiated in experimental radiation therapy of both animal and human neoplasia utilizing protons, alpha particles, and carbon ions.