Functional expression of a heterologous major histocompatibility complex class I gene in transgenic mice

Transgenic mouse model for central nervous system demyelination

A common feature of demyelinating diseases such as multiple sclerosis in humans and experimental autoimmune encephalomyelitis in rodents is the marked elevation in the expression of the major histocompatibility complex (MHC) antigens in the involved sites. By specific targeting of a syngeneic MHC class I gene to oligodendrocytes, we have generated transgenic mice which not only exhibit severe involuntary tremors and develop tonic seizures but also show extensive demyelination in both the brain and the spinal cord. The fact that demyelination in these mice occurs in the absence of immune infiltration dismisses an autoimmune involvement but suggests that the MHC class I antigens play a direct role in inducing disease. Our findings lend support to the possibility that demyelinating diseases are induced by infectious agents such as viruses which can either directly activate MHC gene expression in oligodendroglia or indirectly activate expression through the release by reactive T cells of gamma interferon in the brain.

Transgenic mouse model for central nervous system demyelination

A common feature of demyelinating diseases such as multiple sclerosis in humans and experimental autoimmune encephalomyelitis in rodents is the marked elevation in the expression of the major histocompatibility complex (MHC) antigens in the involved sites. By specific targeting of a syngeneic MHC class I gene to oligodendrocytes, we have generated transgenic mice which not only exhibit severe involuntary tremors and develop tonic seizures but also show extensive demyelination in both the brain and the spinal cord. The fact that demyelination in these mice occurs in the absence of immune infiltration dismisses an autoimmune involvement but suggests that the MHC class I antigens play a direct role in inducing disease. Our findings lend support to the possibility that demyelinating diseases are induced by infectious agents such as viruses which can either directly activate MHC gene expression in oligodendroglia or indirectly activate expression through the release by reactive T cells of gamma interferon in the brain.

Alteration of the natural killer repertoire in H-2 transgenic mice: specificity of rapid lymphoma cell clearance determined by the H-2 phenotype of the target

The mechanism behind natural tumor resistance conveyed by a H-2Dd transgene to C57Bl/6 (B6) mice was investigated. Transgenic D8 mice were more efficient than control mice in natural killer (NK) cell mediated rapid elimination of intravenously inoculated radiolabeled lymphoma cells of B6 origin, such as RBL-5. There was no difference between D8 and B6 mice when elimination of YAC-1 targets was monitored. The effect of the transgene on the NK repertoire was related to the H-2 phenotype of the target: the differential elimination of RBL-5 lymphoma cells in D8 and B6 mice was not seen when a H-2 deficient variant of this line was used (efficiently eliminated in both genotypes), nor was it seen with a H-2Dd transfectant (surviving in both genotypes). The data show that a MHC class I transgene can directly control natural killing in vivo by altering the repertoire rather than the general levels of NK activity. Since the NK mediated elimination seen after introduction of a novel gene in the host was neutralized by introducing the same gene (H-2Dd), but not an unrelated class I gene (H-2Dp), in the tumor, the data support the concept of NK surveillance against missing self. This combined transgenic/transfectant system may serve as a tool for a molecular dissection of the interactions between NK cells and their targets in vivo.

Extinction of JC virus tumor-antigen expression in glial cell--fibroblast hybrids

JC virus (JCV) is a ubiquitous human papovavirus that shares sequence and structural homology with simian virus 40 (SV40). In contrast to SV40, expression of JCV is restricted to a small number of cell types, including human fetal glial cells, uroepithelial cells, amnion cells, and some endothelial cells. To study the control of JCV early region expression, we made heterokaryons and stable hybrids between JCV-transformed hamster glial cells and mouse fibroblasts. Binucleate heterokaryons exhibited extinction of large tumor antigen expression in the hamster nuclei as assayed by indirect immunofluorescence. This extinction was both time and dose dependent: extinction reached maximal levels at 24-36 hr after fusion and was dependent on the ratio of glial cell to fibroblast nuclei in multinucleated heterokaryons. Extinction also was observed in stable hybrids between the glial cells and mouse Ltk- cells. Southern blot analysis showed that the extinguished hybrids contained viral sequences. Reexpression of large tumor antigen was observed in several subclones, suggesting that extinction was correlated with the loss of murine fibroblast chromosomes from these hybrids. The cis-acting region that mediates extinction resides within the viral regulatory region, which contains two 98-base-pair repeats that have enhancer activity. These data demonstrate that cellular factors that negatively regulate viral gene expression contribute to the restricted cell-type specificity of this virus.

Natural resistance against lymphoma grafts conveyed by H-2Dd transgene to C57BL mice

The H-2Dd transgenic strain D8 on C57BL background was more resistant to subcutaneous challenge of RBL-5 lymphoma cells than B6 controls. The direct role of the H-2Dd antigen was investigated by the use of (D8 x B6)F1 crosses and (D8 B6) x B6 backcrosses. The latter showed cosegregation with regard to Dd antigen expression and lymphoma resistance, both of which were inherited in a pattern consistent with control by a single dominant gene. The rejection potential in (D8 x B6)F1 mice appeared as strong as that seen in crosses between B6 and MHC congenic mice (on B10 background) carrying H-2Dd. The lymphoma resistance could be abrogated by treatment with anti-asialo GM1 antiserum or anti-NK 1.1 mAb, indicating a role for NK cells.