Genetic linkage and cell distribution analysis of T cell alloantigens in the rat

Preservation of GLUT 2 expression in islet beta cells of Kilham rat virus (KRV)-infected diabetes-resistant BB/Wor rats

Loss of GLUT 2, the glucose transporter isoform of pancreatic beta cells, has been reported to accompany the onset and perhaps contribute to the pathogenesis, of insulin-dependent and non-insulin-dependent diabetes mellitus in BB/Wor and Zucker fatty rats. In this study we investigated the effect of Kilham Rat Virus infection on GLUT2 expression in diabetes-resistant BB/Wor rats. Viral antibody-free diabetes-resistant rats do not develop spontaneous diabetes, but inoculation with Kilham Rat Virus induces autoimmune beta-cell destruction and hyperglycaemia. Pancreas sections from normoglycaemic diabetes-resistant BB/Wor rats were obtained 5, 7 and 25 days after inoculation with Kilham Rat Virus and stained for GLUT2 using a rabbit polyclonal antibody. At all time points, beta cells displayed GLUT2 expression comparable to uninfected diabetes-resistant controls. Immunostained insulin content of the beta cells also remained unchanged. Sections were also examined from Kilham Rat Virus inoculated diabetes-resistant rats with lymphocytic insulitis or diabetes. GLUT2 and insulin immunostaining were unchanged in non-diabetic rats with early insulitis. GLUT2 beta-cell staining was variably reduced in diabetic rats with established insulitis and reduced beta-cell insulin immunostaining. Hence, the initial stages of Kilham Rat Virus-induced diabetes in diabetes-resistant rats are not accompanied by a significant reduction in GLUT2 expression. These results suggest that the loss of GLUT2 does not play a significant role in the aetiology of diabetes in the Kilham Rat Virus-infected diabetes-resistant BB/Wor rat.

Loss of RT6 message and most circulating T cells after thymectomy of diabetes prone BB rats

T cells expressing the RT6 surface alloantigen perform important immunoregulatory functions in the rat. Diabetes prone (DP) BB rats are deficient in circulating RT6+ T cells and develop spontaneous autoimmune diabetes mellitus. Transfusions leading to engraftment of RT6+ T cells prevent the disease. Coisogenic diabetes resistant (DR) BB rats do circulate RT6+ T cells and are free of disease. We investigated the basis for the deficiency of RT6+ T cells in the DP-BB rat and made the following observations. 1. Thymectomy causes the rapid loss of most peripheral T cells in the DP-BB rat. 2. Concomitant with the loss of T cells is the total loss of mRNA encoding RT6. 3. In contrast to the effects observed in peripheral lymphoid tissues, thymectomy does not lead to a detectable loss in RT6+ protein found in the small intestine. We conclude that the deficiency of RT6+ peripheral T cells in the DP-BB rat is due either to their short life span or to their reduced proliferative capacity following release from the thymus.

Identification of functional T cell subsets and surface antigen changes during activation as they relate to RT6

The functional and phenotypic heterogeneity of the rat peripheral T lymphocyte antigen RT6 has been examined. The in vivo popliteal graft-vs-host reaction (GvHR), in vitro MLR, and the generation and effector populations of cytotoxic T lymphocyte were used to examine the response of RT6-positive (RT6+) or -negative (RT6-) subsets of CD4 and CD8 T cells to alloantigen. T lymphocytes with the CD4+RT6+ surface phenotype are necessary and sufficient for inducing a strong GvHR. T lymphocytes with the CD4+RT6-, CD8+RT6+, and CD8+RT6- surface phenotypes do not contribute or induce a strong GvHR. Both the CD4+RT6+ and the CD4+RT6- T cells proliferate in the MLR assay. CTL precursors are a mixture of CD8+RT6+ and CD8+RT6- phenotypes, but only cells bearing the RT6- phenotype are potent CTL effector cells. Data presented in this paper also demonstrate that the RT6.1 alloantigen, present on the majority of rat T cells, modulates on cortisone-resistant thymocytes (CRT) and peripheral T cells. Although freshly isolated CRTs do not express the RT6.1 epitope, RT6+ cells develop when CRTs are placed into culture. Peripheral T cells that are RT6- will also become RT6+ in culture. Stimulation of T cell cultures with a mitogen causes the loss of the RT6.1 antigen, as detected by the DS4.23 mAb. The effect is more pronounced in cultures of CRTs than peripheral T cells. Following a return to a nonactivated state, the T cells reexpress RT6. The loss and reexpression of RT6 may be related to activation and/or differentiation of T cells.

Characterization of RT6 bearing rat lymphocytes. I. Ontogeny of the RT6+ subset

The RT6 alloantigen is present on approximately 70% of peripheral T cells in the rat, but is absent from thymocytes and bone marrow lymphocytes. The results of further phenotypic analysis in the present study demonstrated that the RT6 alloantigen is expressed on approximately 45% of the helper/inducer (CD4; W3/25+) and 80% of the cytotoxic/suppressor (CD8; OX8+) peripheral T-cell subsets. Ontogenetic and thymus ablation studies indicated that the RT6+ T-cell subset is thymus-dependent and normally develops after the appearance of RT6-T cells in neonatal rats, and that the expression of RT6 is a post-thymic maturational event. Furthermore, intrathymic adoptive transfer of bone marrow cells demonstrated that RT6+ T cells are thymus-derived cells. These results show that most if not all RT6+ T cells are the progeny of RT6- T cells. However, they do not exclude the possibility that a separate lineage of RT6- T cells exists, which also has OX8+ and W3/25+ subsets. The possible developmental and functional relationships of RT6- and RT6+ T cells in the rat are discussed.

Genetic linkage in the Norway rat

The present status of research on genetic linkage is reviewed. Where possible, the data are statistically combined to give consolidated estimates of the recombination value. Ten groups of linked genes have been determined. The first assignments of linkage groups to specific chromosomes have been facilitated by inter-species cell hybridisation.

Isolation and characterization of protective T cells induced by Listeria monocytogenes

Rats convalescing from a recent infection with Listeria monocytogenes generate T cells which can protect recipient rats against a challenge infection with that organism. Using monoclonal antibodies that react with some but not all rat peripheral T cells, the T-cell mediators of acquired resistance to infection (TCRI) were isolated by panning and characterized by using a fluorescence-activated cell sorter. Many L. monocytogenes-immune TCRI were relatively large cells as judged by their light-scattering properties. That finding accords with previously reported cytokinetic data and velocity sedimentation analyses which revealed that the majority of L. monocytogenes-immune TCRI are lymphoblasts. In the current investigation, the surface antigenic profile of these mediator T cells was revealed as W3/25+ OX8+ OX4+ RT6.1-. That phenotype is identical to that of L. monocytogenes-induced prekiller cells which are formed as part of the animal's cell-mediated response to infection. Like prekiller cells and their differentiated counterparts, L. monocytogenes-immune TCRI adhere preferentially to monolayers of syngeneic fibroblasts. The results indicate that L. monocytogenes-immune TCRI belong to a minor subset of peripheral T cells which also contains T cells that have the cytotoxic potential by which L. monocytogenes-induced prekiller cells have been defined.