The early days of NK cells: an example of how a phenomenon led to detection of a novel immune receptor system - lessons from a rat model

TALEN-mediated generation of Nkx3.1 knockout rat model

BACKGROUND

Recent developments in gene editing, using transcriptional activator-like effector nucleases (TALENs), have greatly helped the generation of genetically engineered animal models. The NK3 homeobox 1 (NKX3.1) protein plays important roles in prostate development and protein production, and functions as a tumor suppressor. Recently, NKX3.1 was shown to be associated with breast cancer in humans.

METHODS

Our aim was to create a new rat model to elucidate the functions of NKX3.1. To that end, we generated Nkx3.1 knockout rats using TALENs and analyzed their phenotype. TALEN-mediated Nkx3.1 knockout was confirmed by T7 endonuclease I (T7E1) assay and DNA sequencing. Prostate weight and fertility were evaluated in the knockout rats, besides determining the proportion of epithelial cells and messenger RNA (mRNA) expression of genes associated with carcinogenesis. Breast tumors were examined by histopathology.

RESULTS

Results suggested Nkx3.1 knockout rats have reduced fertility, decreased prostate weights, and increased epithelial cell layers. The mRNA expression of genes related to prostate carcinogenesis, namely Ar, Akt, and Pi3k, also increased. Moreover, the Nkx3.1 knockout rats often developed malignant breast tumors.

CONCLUSIONS

We, therefore, successfully created the first Nkx3.1 knockout rat model, using TALEN-mediated gene targeting, and used it to identify defects associated with Nkx3.1 deficiency, not previously observed in mice. Loss of Nkx3.1 in rats led to lower reproductive capacity, and decreased prostate weights, apart from the risk of developing breast cancer. We, thus, proposed Nkx3.1 knockout rats as reliable models for studying the role of NKX3.1 in decreased prostate weights, fertility, and breast cancer, as well as in prostate cancer.

The Toll-Like Receptor 3 Agonist Polyriboinosinic Polyribocytidylic Acid Increases the Numbers of NK Cells with Distinct Phenotype in the Liver of B6 Mice

One of the activating factors of the cells of the innate immune system is the agonists of toll-like receptors (TLRs). Our earlier publications detailed how poly(I:C), a TLR3 agonist, elevates the NK cell population and the associated antigen-specific CD8⁺ T cell responses. This study involved a single treatment of the B6 mice with poly(I:C) intraperitoneally. To perform a detailed phenotypic analysis, mononuclear cells were prepared from each of the liver, peripheral blood, and spleen. These cells were then examined for their NK cell population by flow cytometric analysis following cell staining with indicated antibodies. The findings of the study showed that the NK cell population of the liver with an NK1.1^highCD11b^highCD11c^high B220⁺Ly6G^- phenotype was elevated following the treatment with poly(I:C). In the absence of CD11b molecule (CR3^-/- mice), poly(I:C) can still increase the remained numbers of NK cells with NK1.1⁺CD11b^- and NK1.1⁺Ly6G^- phenotypes in the liver while their numbers in the blood decrease. After the treatment with anti-AGM1 Ab, which induced depletion of NK1.1⁺CD11b⁺ cells and partial depletion of CD3⁺NK1.1⁺ and NK1.1⁺CD11b^- cell populations, poly(I:C) normalized the partial decreases in the numbers of NK cells concomitant with increased numbers of NK1.1^-CD11b⁺ cell population in both liver and blood. Regarding mice with a TLR3^-/- phenotype, their injection with poly(I:C) resulted in the partial elevation in the NK cell population as compared to wild-type B6 mice. To summarise, the TLR3 agonist poly(I:C) results in the elevation of a subset of liver NK cells expressing the two myeloid markers CD11c and CD11b. The effect of poly(I:C) on NK cells is partially dependent on TLR3 and independent of the presence of CD11b.

Novel Targeting to XCR1+ Dendritic Cells Using Allogeneic T Cells for Polytopical Antibody Responses in the Lymph Nodes

Vaccination strategy that induce efficient antibody responses polytopically in most lymph nodes (LNs) against infections has not been established yet. Because donor-specific blood transfusion induces anti-donor class I MHC antibody production in splenectomized rats, we examined the mechanism and significance of this response. Among the donor blood components, T cells were the most efficient immunogens, inducing recipient T cell and B cell proliferative responses not only in the spleen, but also in the peripheral and gut LNs. Donor T cells soon migrated to the splenic T cell area and the LNs, with a temporary significant increase in recipient NK cells. XCR1⁺ resident dendritic cells (DCs), but not XCR1⁻ DCs, selectively phagocytosed donor class I MHC⁺ fragments after 1 day. After 1.5 days, both DC subsets formed clusters with recipient CD4⁺ T cells, which proliferated within these clusters. Inhibition of donor T cell migration or depletion of NK cells by pretreatment with pertussis toxin or anti-asialoGM₁ antibody, respectively, significantly suppressed DC phagocytosis and subsequent immune responses. Three allogeneic strains with different NK activities had the same response but with different intensity. Donor T cell proliferation was not required, indicating that the graft vs. host reaction is dispensable. Intravenous transfer of antigen-labeled and mitotic inhibitor-treated allogeneic, but not syngeneic, T cells induced a polytopical antibody response to labeled antigens in the LNs of splenectomized rats. These results demonstrate a novel mechanism of alloresponses polytopically in the secondary lymphoid organs (SLOs) induced by allogeneic T cells. Donor T cells behave as self-migratory antigen ferries to be delivered to resident XCR1⁺ DCs with negligible commitment of migratory DCs. Allogeneic T cells may be clinically applicable as vaccine vectors for polytopical prophylactic antibody production even in asplenic or hyposplenic individuals.

Listeria monocytogenes infection enhances the interaction between rat non-classical MHC-Ib molecule and Ly49 receptors

Murine NK cell Ly49 receptors, functionally analogous to KIRs in humans recognize MHC class I molecules and play a key role in controlling NK cell function. We have previously shown that the paired activating Ly49s4 and inhibitory Ly49i4 receptors recognize undefined non-classical MHC-Ib ligands from the RT1-CE region in rats. Here, the RT1-CE16 gene of the RT1^d haplotype was stably transfected into the mouse RAW macrophage cell line, termed RAW-CE16^d cells. Combining RAW-CE16^d cells with Ly49 expressing reporter cells demonstrated Ly49i4 and Ly49s4 specificity for CE16^d. The Ly49s4/i4:CE16^d interaction was confirmed by specific MHC-I blocking monoclonal Abs. Further, we used our in vitro model to study the effect of Listeria monocytogenes (LM) on CE16^d after infection. LM infection and IFN-γ stimulation both led to enhanced CE16^d expression on the surface of transfected RAW-CE16^d cells. Interestingly, the reporter cells displayed increased response to LM-infected RAW-CE16^d cells compared with IFN-γ-treated RAW-CE16^d cells, suggesting a fundamental difference between these stimuli in supporting enhanced Ly49 recognition of CE16^d. Collectively, our data show that Ly49s4 and Ly49i4 recognize the non-classical RT1-CE16^d molecule, which in turn is up-regulated during LM infection and thereby may contribute to NK-mediated responses against infected cells.

Generation of TALEN-mediated FH knockout rat model

Transcription activator-like effector nucleases (TALENs) are valuable tools for precise genome engineering of laboratory animals. Here we utilized this technique for efficient site-specific gene modification to create a fumarate hydratase (FH) gene knockout rat model, in which there was an 11 base-pair deletion in the first exon of the FH gene in 111 rats. 18 live-born targeted mutation offsprings were produced from 80 injected zygotes with 22.5% efficiency, indicating high TALEN knockout success in rat zygots. Only heterozygous deletion was observed in the offsprings. Sixteen pairs of heterozygous FH knockout (FH+/−) rats were arranged for mating experiments for six months without any homozygous KO rat identified. Sequencing from the pregnant rats embryo samples showed no homozygous FH KO, indicating that homozygous FH KO is embryonically lethal. Comparatively, the litter size was decreased in both male and female FH+/− KO rats. There was no behaviour difference between the FH+/− KO and the control rats except that the FH+/− KO male rats showed significantly higher body weight in the 16-week observation period. Clinical haematology and biochemical examinations showed hematopoietic and kidney dysfunction in the FH+/− KO rats. Small foci of anaplastic lesions of tubular epithelial cells around glomeruli were identified in the FH+/− kidney, and these anaplastic cells were comparatively positive for Ki67, p53 and Sox9, and such findings are most probably related to the kidney dysfunction reflected by the biochemical examinations of the rats. In conclusion, we have successfully established an FH+/− KO rat model, which will be useful for further functional FH studies.

Identification of MHC Class Ib Ligands for Stimulatory and Inhibitory Ly49 Receptors and Induction of Potent NK Cell Alloresponses in Rats

Early studies indicate that rats may have a repertoire of MHC class Ib-reactive Ly49 stimulatory receptors capable of mounting memory-like NK cell alloresponses. In this article, we provide molecular and functional evidence for this assumption. Pairs of Ly49 receptors with sequence similarities in the lectin-like domains, but with opposing signaling functions, showed specificity for ligands with class Ia-like structural features encoded from the first telomeric MHC class Ib gene cluster, RT1-CE, which is syntenic with the H2-D/H2-L/H2-Q cluster in mice. The activating Ly49s4 receptor and its inhibitory counterparts, Ly49i4 and Ly49i3, reacted with all allelic variants of RT1-U, whereas Ly49s5 and Ly49i5 were specific for RT1-E^u NK cell cytolytic responses were predictably activated and inhibited, and potent in vivo NK alloresponses were induced by repeated MHC class Ib alloimmunizations. Additional Ly49-class Ib interactions, including RT1-C^l with the Ly49s4/Ly49i4/Ly49i3 group of receptors, were characterized using overexpressed receptor/ligand pairs, in vitro functional assays, and limited mutational analyses. Obvious, as well as subtle, Ly49-class Ib interactions led to ligand-induced receptor calibration and NK subset expansions in vivo. Together, these studies suggest that in vivo NK alloresponses are controlled by pleomorphic Ly49-class Ib interactions, some of which may not be easily detectable in vitro.

Immunogenetics of type 1 diabetes: A comprehensive review

Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing beta cells in the pancreas. Prevention of T1D will require the ability to detect and modulate the autoimmune process before the clinical onset of disease. Genetic screening is a logical first step in identification of future patients to test prevention strategies. Susceptibility to T1D includes a strong genetic component, with the strongest risk attributable to genes that encode the classical Human Leukocyte Antigens (HLA). Other genetic loci, both immune and non-immune genes, contribute to T1D risk; however, the results of decades of small and large genetic linkage and association studies show clearly that the HLA genes confer the most disease risk and protection and can be used as part of a prediction strategy for T1D. Current predictive genetic models, based on HLA and other susceptibility loci, are effective in identifying the highest-risk individuals in populations of European descent. These models generally include screening for the HLA haplotypes "DR3" and "DR4." However, genetic variation among racial and ethnic groups reduces the predictive value of current models that are based on low resolution HLA genotyping. Not all DR3 and DR4 haplotypes are high T1D risk; some versions, rare in Europeans but high frequency in other populations, are even T1D protective. More information is needed to create predictive models for non-European populations. Comparative studies among different populations are needed to complete the knowledge base for the genetics of T1D risk to enable the eventual development of screening and intervention strategies applicable to all individuals, tailored to their individual genetic background. This review summarizes the current understanding of the genetic basis of T1D susceptibility, focusing on genes of the immune system, with particular emphasis on the HLA genes.

Avoiding immunological rejection in regenerative medicine

One of the major goals of regenerative medicine is repair or replacement of diseased and damaged tissues by transfer of differentiated stem cells or stem cell-derived tissues. The possibility that these tissues will be destroyed by immunological rejection remains a challenge that can only be overcome through a better understanding of the nature and expression of potentially immunogenic molecules associated with cell replacement therapy and the mechanisms and pathways resulting in their immunologic rejection. This review draws on clinical experience of organ and tissue transplantation, and on transplantation immunology research to consider practical approaches for avoiding and overcoming the possibility of rejection of stem cell-derived tissues.