DNA sequence analysis of the rat RT1.B alpha gene

A modified heterotopic heart transplantation in the rat - as an important model in experimental regeneration and replacement of the failing organ

The qualification of new knowledge is one of the oldest problems in experimental medicine that provides a link between fundamental discovery, hypothesis, ‘proof of concept’ preclinical studies and development of clinical trials. The biggest challenge in animal models is the proper evaluation of all the aspects that are crucial in specific studied pathologies as well as the prediction of their progression. The aim of this review was to describe and discuss the rat animal model of heart transplant. The rat model of heart transplantation is an excellent yet underestimated method of research of prevention, monitoring and treatment of acute and chronic, immune and nonimmune response to organ transplantation. Despite being a technically and logistically demanding model, it provides a tool for reproducible experiments with longterm animal survival and excellent graft survival.

Complementary DNA sequences encoding the rat MHC class II RT1-Bu and RT1-Du alpha and beta chains

The rat major histocompatibility complex loci RT1-B and RT1-D are equivalent to the human leucocyte antigens HLA-DQ and HLA-DR respectively. Here we describe the complementary DNA (cDNA) sequence encoding the alpha and beta chains of both the RT1-B and RT1-D locus genes of the rat RT1u haplotype. We have found entire sequence identity between five different inbred rat strains of the RT1u haplotype, which differs from previously published, incomplete sequences. This information is of considerable value for experimental studies of transplantation immunity and autoimmune disease.

Overexpression of glia maturation factor in astrocytes leads to immune activation of microglia through secretion of granulocyte-macrophage-colony stimulating factor

We infected a mixed culture of primary rat astrocytes and microglia with a replication-defective adenovirus carrying the rat glia maturation factor (GMF) cDNA. Affymetrix microarray analysis showed a big increase in the expression of several major histocompatibility complex (MHC) class II proteins along with interleukin-1beta (IL-1beta). Subsequent study using reverse transcription-polymerase chain reaction (RT-PCR) yielded the same results with the mixed culture, but not with pure astrocytes or pure microglia. We also noticed that the GMF/virus construct infected only astrocytes but not microglia. This led us to suspect that overexpression of GMF in astrocytes resulted in the secretion of an active substance that stimulated the microglia to express MHC II and IL-1beta. We identified this substance as granulocyte-macrophage-colony stimulating factor (GM-CSF). MHC II are unique to antigen-presenting cells such as microglia and monocytes. The results suggest that GMF in astrocytes can initiate a series of events, leading to immune activation in the nervous system, and implicates its involvement in autoimmune diseases such as multiple sclerosis.

IFN-γ Increases the Severity and Accelerates the Onset of Experimental Autoimmune Uveitis in Transgenic Rats

Experimental autoimmune uveitis (EAU) is a predominantly Th1-mediated intraocular inflammatory disease that serves as a model for studying the immunopathogenic mechanisms of uveitis and organ-specific autoimmune diseases. Despite the well-documented role of IFN-γ in the activation of inflammatory cells that mediate autoimmune pathology, recent studies in IFN-γ-deficient mice paradoxically show that IFN-γ confers protection from EAU. Because of the implications of these findings for therapeutic use of IFN-γ, we sought to reexamine these results in the rat, another species that shares essential immunopathologic features with human uveitis and is the commonly used animal model of uveitis. We generated transgenic rats (TR) with targeted expression of IFN-γ in the eye and examined whether constitutive ocular expression of IFN-γ would influence the course of EAU. We show here that the onset of rat EAU is markedly accelerated and is severely exacerbated by IFN-γ. In both wild-type and TR rats, we found that the disease onset is preceded by induction of ICAM-1 gene expression and is characterized by selective recruitment of T cells expressing a restricted TCR repertoire in the retina. In addition, these events occur 2 days earlier in TR rats. Thus, in contrast to the protective effects of IFN-γ in mouse EAU, our data clearly show that intraocular secretion of IFN-γ does not confer protection against EAU in the rat and suggest that IFN-γ may activate distinct immunomodulatory pathways in mice and rats during uveitis.

The marsupial MHC: the tammar wallaby, Macropus eugenii, contains an expressed DNA-like gene on chromosome 1

In the placental mammal major histocompatibility complex (MHC) three main families of class II genes, DR, DQ, and DP, have been recognized. Each family contains genes that code for one or more A- and B-chains. Recent evidence has indicated that a fourth family can be described, the DN/DO family. These four families arose sometime early in mammalian evolution. Our purpose was to deduce the MHC of an early mammalian ancestor of marsupials and eutherians. Using primers designed to conserved regions in exon 2 and exon 3 of the DQA gene we amplified an 830-bp band from the total genomic DNA of the marsupial, Macropus eugenii (tammar wallaby). However, sequence analysis of cloned genomic products showed that the primers had amplified three genes, two of which appeared to be alleles at one locus, while the other gene belonged to a closely related locus. Phylogenetic analysis showed that both these loci were most closely related to the human (HLA-DNA) and mouse (H-20a) DNA genes, with a bootstrap support of 78%. Expression of only one locus could be detected by RT-PCR from spleen RNA. In situ hybridization to tammar wallaby chromosomes mapped these genes to one region on the long arm of chromosome 1, indicating the position of the MHC in marsupials. Related A-chain genes were detected in monotremes, and human by southern blotting, and very faint bands were observed in the chicken. Hybridization with a tammar DNA-like gene on several marsupial species showed evidence of at least three DNA-like loci in the tammar wallaby, at least one in the koala, but none in the kowari. This indicates that the organization of the class II MHC may be more dynamic in marsupial than in placental mammals, but, in contrast to a previous study on the MHC of a marsupial, we cannot conclude that the class II gene families of placental and marsupial mammals evolved from different ancestral genes.

Isolation, characterization and evolution of ovine major histocompatibility complex class II DRA and DQA genes

Four full-length ovine major histocompatibility complex (MHC) class II A cDNA clones coding for new alleles of DRA, DQA1 and DQA2 genes were isolated from two ovine lambda gt10 cDNA libraries. The derived amino acid sequences of these clones resemble class II A molecules from other species in both size and structure. Restriction fragment length polymorphism analysis, using an Ovar-DRA probe on DNA from Merino and Romney sheep revealed only limited polymorphism in contrast to the high levels of polymorphism revealed by Ovar-DQA probes. Comparison of the predicted amino acid sequences for the three ovine A genes with class II A genes from five other species revealed that the most variable region of the molecule is the signal peptide. Although virtually every amino acid site shows variation, within or between species, there are some blocks of highly conserved residues. Within gene comparisons of nucleotide differences reveal that the greatest number of changes is found between the alleles of Ovar-DQA1 and -DQA2 genes and the least between Ovar-DRA1 alleles. Phylogenetic analysis of class II A sequences from several species place DRA and DQA genes on two distinct branches, with Ovar-DRA1 and BOLA-DRA, and Ovar-DQA1 and BOLA-DQA being most similar on their respective branches.

Nucleotide sequence, polymorphism, and evolution of ovine MHC class II DQA genes

The nucleotide sequence of all exons and introns, excluding exon 1, of the ovine major histocompatibility complex (MhcOvar) genes analogous to the HLA-DQA1 and -DQA2 genes has been determined and the gene structure found to be similar to that reported for other species. The predicted amino acid sequences of the Ovar-DQA genes have been compared with the equivalent DQA genes in man, mouse, rat, rabbit, and cattle and used to determine the evolutionary relationships of the sheep class II genes to these other species. Northern blot analysis of sheep mRNA using exon specific probes for each of the two Ovar-DQA genes show that both genes are transcribed, whereas in humans there is no evidence that HLA-DQA2 is transcriptionally active. Restriction fragment length polymorphisms (RFLPs) have been used to define a polymorphic series of alleles in both Ovar-DQA genes and have indicated that the number of DQA genes is not constant in sheep as it is in humans, but varies with the haplotype.

Protein kinase C regulates MHC-class II expression on endothelial cells

Cultured endothelial cells (EC) were negative for class II antigen in native state, whereas 49% of the endothelial cells began to express this antigen after 24 h of interferon-gamma (IFN-gamma) stimulation. IFN-gamma induced relatively slowly the elevation of class II antigen on endothelial cells, since it took more than 10 h before the first signs of mRNA signal of class II were detected. Class II antigen instead began to appear during 16-20 h after the initiation of IFN-gamma treatment. Committed step analysis revealed that IFN-gamma could not be washed away at any time point without affecting the number of class II positive cells after a 24-h incubation period. Protein kinase C (PKC) activator phorbol-12-myristate-13-acetate (PMA) could partially mimic IFN-gamma effect in inducing class II expression on endothelial cells. PMA together with another PKC activator arachidonic acid (AA) induced class II expression on endothelial cells as well as IFN-gamma. The crucial role of activation of PKC in the IFN-gamma induced class II expression can also be demonstrated by using PKC inhibitors in combination with IFN-gamma. PKC inhibitor H7 was able to decrease almost totally IFN-gamma induced class II induction both on the mRNA as well as on the protein level. PKC activation has often been linked to its translocation from the cytosolic compartment to the inner surface of the plasma membrane. IFN-gamma induced a transient 2.4-fold increase in the membrane-associated PKC in endothelial cells within 10 min after the initiation of the stimulus. Taken together these data show that IFN-gamma requires a long time before class II induction. The regulation of class II expression occurs at transcriptional level and requires de novo protein synthesis as shown by cycloheximide inhibition.

cis-acting sequences required for class II gene regulation by interferon gamma and tumor necrosis factor alpha in a murine macrophage cell line

In this report, we have demonstrated that IFN-gamma and TNF-alpha increase expression of both the I-A and I-E region gene products on the surface of the myelomonocytic cell line WEHI-3, and that they mediate this increase via an increase in A alpha transcription. Constructs containing 5' deletion mutations of the A alpha promoter attached to the bacterial chloramphenicol acetyl transferase gene were used to delineate the minimum 5' flanking sequences required for promoter activity, and for inducibility by IFN-gamma and TNF-alpha. Approximately 115 bp of 5' sequences are required for minimum induction by IFN-gamma or TNF-alpha when the cytokines are present separately. This includes the three conserved promoter elements, the X, Y, and H boxes. Nested linker-scanner mutations demonstrated that additional regions were also critical for optimal induction by IFN-gamma or TNF-alpha. These include the kappa B-like enhancer and a TNF-alpha-specific sequence that we have tentatively called the T box. The T box sequence was also found in the promoter regions of the human HLA-DQ alpha and rat RT1.B alpha genes. Although the entire T box sequence element was not found in the other mouse class II genes, all class II alpha genes contained the SV40 core enhancer element in the regions included by the T box. Mouse class II beta genes appear to contain neither the T box nor the core enhancer element in this region, suggesting differential regulation of class II alpha and beta genes by TNF-alpha.