Nature of T-cells resident in spleens of thymectomized, lethally irradiated, bone marrow-reconstituted mice

High-fat diet- and angiotensin II-induced aneurysm concurrently elicits splenic hypertrophy

BACKGROUND

Angiotensin II (Ang II) and high-fat diet are implicated in causing pathological changes in the vascular endothelium, brain, kidney and liver. The association of aneurysm leading to histopathological changes in the splenic compartment remains elusive. Further, the salubrious credentials of antioxidants, especially α-tocopherol and β-carotene in the resolution of splenic pathology have not been investigated.

METHODS

Four-month-old Apoe(-/-) mice were used in the induction of aneurysm by infusing Ang II, and subsequently were orally administered with α-tocopherol and β-carotene-enriched diet for 60 days.

RESULTS

We observed splenomegaly in Ang II-infused aneurysm and high-fat diet-supplemented mice as compared to normal mice. These observations were further confirmed through histopathological investigations, demonstrating splenic follicular hypertrophy. We observed a remarkable decrease in the size of spleen in α-tocopherol and β-carotene-treated Apoe(-/-) mice as compared with Ang II-treated animals. Furthermore, no marked changes in the histopathological splenic sections were seen in the β-carotene-treated group. However, hyperplasia and proliferation of immature lymphocytes in the follicles were observed in the α-tocopherol-treated animals. We found that CD4+ T-cell levels were increased in the high-fat diet group relative to the control group and were decreased in the β-carotene-treated animals.

CONCLUSIONS

Our study provides evidence that Ang II infusion and high-fat supplementation induces abdominal aortic aneurysm that has pathological implications to the spleen. The use of β-carotene but not α-tocopherol as an antioxidant markedly ameliorates the pathological changes in spleen.

Mechanisms of allografted tumor rejection: the roles of T cells in allograft rejection mediated by a type of bone marrow-derived macrophage

Allografted tumor rejection does not occur in the absence of T cells, but the main effector cells responsible for the rejection are allograft-induced macrophages (AIM). We examined the roles of T cells in the AIM-mediated rejection of Meth A (H-2d) tumor cells from C57BL/6 (H-2b) mice. Irradiation of C57BL/6 mice abrogated both the induction of AIM and the allograft rejection. Reconstitution of the irradiated mice with F1 (C57BL/6 X C3H/He: H-2b/k) bone marrow cells led to the appearance of H-2b/k haplotype of AIM exclusively in the rejection site and to allograft rejection, indicating that radiosensitive cells prerequisite for both the induction of AIM and allograft rejection were bone marrow-derived cells, and that the progenitors of AIM existed in the bone marrow cells to be activated into AIM in the rejection site. To understand the role of T cells in the induction of AIM, we used adult-thymectomized, X-irradiated C57BL/6 mice reconstituted with F1 bone marrow (ATXBM). The ATXBM mice could neither induce AIM nor reject allogeneic Meth A cells, whereas adoptive transfer of F1 lymph node T cells to the ATXBM mice restored not only the induction of AIM but also rejection of the allograft. Among the lymph node T cells, CD4-, but not CD8+, cells were found to be essential for the activation of AIM progenitors to AIM; and CD8+ T cells were further required for rejection, at least in part, to enhance the number of AIM in the rejection site.

Immediate and long-term effects of radiation on the immune system of specific-pathogen-free mice

Studies on the immediate and long-term effects of radiation on the immune system of specific-pathogen-free mice are summarized in this paper. There was a striking difference in the radiation response of lymphocyte subsets; B cells consist of a fairly radiosensitive homogeneous population, whereas T cells consist of a large percentage (greater than 90 per cent) of radiosensitive and a small percentage (less than 10 per cent) of extremely radioresistant subpopulations. Ly 1+ and Ly 2+ lymphocytes appear equally radiosensitive, although the percentage of radioresistant cells was slightly larger for the former (approximately 5.5 per cent) than the latter (approximately 2.5 per cent). There was a significant strain difference in the radiosensitivity of immune-response potential in mice; immunocompetent cells of C3H mice were more radioresistant than those of BALB/c, C57BL/6, and B10.BR mice. Studies on the long-term effect of radiation on immune system in mice indicated no evidence for accelerated ageing of the immunologic functions when radiation exposure was given to young adults. Preliminary results on the enhancing effect of low dose radiation on cytotoxic T cell response in vitro are also discussed.

Reduced susceptibility of T cell-deficient rats to induction of experimental allergic neuritis

Lewis rats were made deficient in T cells by adult thymectomy and lethal irradiation, and then reconstituted with T cell-free bone marrow. Their ability to develop experimental allergic neuritis (EAN) was compared with normal rats. The majority of T cell-deficient rats remained clinically and histologically unaffected, whereas all but one of the normal rats developed severe EAN. Those T cell-deficient animals which succumbed to EAN were found to have a significantly higher percentage of residual blood T lymphocytes than those which did not. Full susceptibility to EAN was restored by an inoculum of whole thoracic duct lymphocytes (TDL) from normal animals but not by TDL depleted of T cells. The results therefore provide direct confirmation that T cells are a requirement for the development of EAN.

H-2 restriction specificity of T cells from H-2 incompatible radiation bone marrow chimeras: further evidence for the absence of crucial influence of the host/thymus environment on the generation of H-2 restricted TNP-specific T lymphocyte precursors

Experiments were conducted to answer the questions related to (a) the role played by the antigen-presenting cells (APCs) present within the thymus and (b) the effect of radiation dose to the recipients on the H-2 restriction profile of TNP-specific cytotoxic T lymphocyte precursors (CTLP) recovered from spleens and/or thymuses of H-2 incompatible radiation bone marrow chimeras (BMC). The H-2 restriction profile of intrathymically differentiating TNP-specific CTLPs was also analyzed in order to test an argument that donor-H-2 restricted CTLP detected in spleens of H-2 incompatible BMC were due to the extrathymically differentiated T cells under the influence of donor-derived lymphoreticular cells. The results indicated the following: (i) splenic T cells from B10(H-2b) leads to (B10(H-2b) leads to B10.BR(H-2k)) chimeras, which were constructed by irradiating primary B10 leads to B10.BR chimeras with 1100 R and reconstituting them with donor-type (B10) bone marrow cells as long as 8 months after their construction, manifested restriction specificities for both donor- and host-type H-2, (ii) splenic T cells from two types of (B10 X B10.BR)F1 leads to B10 chimeras which were reconstituted after exposure of the recipients with either 900 or 1100 R with donor-type bone marrow cells generated both donor- and host-H-2 restricted TNP-specific cytotoxic T cells, and (iii) the TNP-specific CTLPs present in the regenerating thymuses of B10.BR leads to B10 and (B10 X B10.BR)F1 leads to B10 chimeras 4 weeks after their construction were also shown to manifest both donor- and host-H-2 restriction specificities. The significance of these findings on the H-2 restriction profile of CTLP generated in BMCs is discussed.

T-cell subpopulations in the bone marrow and spleen from thymectomized, irradiated mice reconstituted with normal or nude bone marrow cells

Adult thymectomized and lethally irradiated (ATxXB) BALB/c mice, reconstituted with either nude or normal bone marrow (BM) cells, have been studied to evaluate numbers and mitogen responsiveness of T cells and T-cell progenitors in the BM and the spleen. Although mice reconstituted with nu/nu cells contained significantly higher numbers of Thy 1.2-positive cells in the BM than mice reconstituted with normal BM cells, smaller in vitro mitogen responses were generally given by the former mice. However, spleen and BM cells of both groups responded to phytohaemagglutinin and to concanavalin A. On the basis of comparisons with responses of BM and spleen cells from normal and ATx mice, anti-Thy 1.2 treatment of cells, and 1 g velocity sedimentation experiments, it is suggested that most mitogen responders in the BM of ATxXB mice are Thy 1.2-negative, pre-thymic T-cell precursors and, accordingly, that these cells are able to differentiate to some extent in the absence of the thymus.