The mouse mutation severe combined immune deficiency (scid) is on chromosome 16

The complement system drives local inflammatory tissue priming by metabolic reprogramming of synovial fibroblasts

Arthritis typically involves recurrence and progressive worsening at specific predilection sites, but the checkpoints between remission and persistence remain unknown. Here, we defined the molecular and cellular mechanisms of this inflammation-mediated tissue priming. Re-exposure to inflammatory stimuli caused aggravated arthritis in rodent models. Tissue priming developed locally and independently of adaptive immunity. Repeatedly stimulated primed synovial fibroblasts (SFs) exhibited enhanced metabolic activity inducing functional changes with intensified migration, invasiveness and osteoclastogenesis. Meanwhile, human SF from patients with established arthritis displayed a similar primed phenotype. Transcriptomic and epigenomic analyses as well as genetic and pharmacological targeting demonstrated that inflammatory tissue priming relies on intracellular complement C3- and C3a receptor-activation and downstream mammalian target of rapamycin- and hypoxia-inducible factor 1α-mediated metabolic SF invigoration that prevents activation-induced senescence, enhances NLRP3 inflammasome activity, and in consequence sensitizes tissue for inflammation. Our study suggests possibilities for therapeutic intervention abrogating tissue priming without immunosuppression.

Cytotoxic effector functions of T cells are not required for protective immunity against fatal Rickettsia typhi infection in a murine model of infection: Role of TH1 and TH17 cytokines in protection and pathology

Endemic typhus caused by Rickettsia (R.) typhi is an emerging febrile disease that can be fatal due to multiple organ pathology. Here we analyzed the requirements for protection against R. typhi by T cells in the CB17 SCID model of infection. BALB/c wild-type mice generate CD4+ TH1 and cytotoxic CD8+ T cells both of which are sporadically reactivated in persistent infection. Either adoptively transferred CD8+ or CD4+ T cells protected R. typhi-infected CB17 SCID mice from death and provided long-term control. CD8+ T cells lacking either IFNγ or Perforin were still protective, demonstrating that the cytotoxic function of CD8+ T cells is not essential for protection. Immune wild-type CD4+ T cells produced high amounts of IFNγ, induced the release of nitric oxide in R. typhi-infected macrophages and inhibited bacterial growth in vitro via IFNγ and TNFα. However, adoptive transfer of CD4+IFNγ-/- T cells still protected 30-90% of R. typhi-infected CB17 SCID mice. These cells acquired a TH17 phenotype, producing high amounts of IL-17A and IL-22 in addition to TNFα, and inhibited bacterial growth in vitro. Surprisingly, the neutralization of either TNFα or IL-17A in CD4+IFNγ-/- T cell recipient mice did not alter bacterial elimination by these cells in vivo, led to faster recovery and enhanced survival compared to isotype-treated animals. Thus, collectively these data show that although CD4+ TH1 cells are clearly efficient in protection against R. typhi, CD4+ TH17 cells are similarly protective if the harmful effects of combined production of TNFα and IL-17A can be inhibited.

Liver Necrosis and Lethal Systemic Inflammation in a Murine Model of Rickettsia typhi Infection: Role of Neutrophils, Macrophages and NK Cells

Rickettsia (R.) typhi is the causative agent of endemic typhus, an emerging febrile disease that is associated with complications such as pneumonia, encephalitis and liver dysfunction. To elucidate how innate immune mechanisms contribute to defense and pathology we here analyzed R. typhi infection of CB17 SCID mice that are congenic to BALB/c mice but lack adaptive immunity. CB17 SCID mice succumbed to R. typhi infection within 21 days and showed high bacterial load in spleen, brain, lung, and liver. Most evident pathological changes in R. typhi-infected CB17 SCID mice were massive liver necrosis and splenomegaly due to the disproportionate accumulation of neutrophils and macrophages (MΦ). Both neutrophils and MΦ infiltrated the liver and harbored R. typhi. Both cell populations expressed iNOS and produced reactive oxygen species (ROS) and, thus, exhibited an inflammatory and bactericidal phenotype. Surprisingly, depletion of neutrophils completely prevented liver necrosis but neither altered bacterial load nor protected CB17 SCID mice from death. Furthermore, the absence of neutrophils had no impact on the overwhelming systemic inflammatory response in these mice. This response was predominantly driven by activated MΦ and NK cells both of which expressed IFNγ and is considered as the reason of death. Finally, we observed that iNOS expression by MΦ and neutrophils did not correlate with R. typhi uptake in vivo. Moreover, we demonstrate that MΦ hardly respond to R. typhi in vitro. These findings indicate that R. typhi enters MΦ and also neutrophils unrecognized and that activation of these cells is mediated by other mechanisms in the context of tissue damage in vivo.

Molecular Pathology of Severe Combined Immunodeficiency in Mice, Horses, and Dogs

Severe combined immunodeficiency (SCID) is an inherited disorder of humans, mice, horses, and dogs, in which affected individuals are incapable of generating antigen-specific immune responses. It occurs when lymphocyte precursors fail to differentiate into mature lymphocytes because of mutations within recombinase-activating genes 1 and 2 or within the genes encoding deoxyribonucleic acid (DNA)-dependent protein kinase (DNA-PK). It also occurs when differentiated lymphocytes are incapable of completing signal transduction pathways because of defects in cell surface receptors for interleukins (IL). A spontaneous mutation in DNA-PKcs of BALB/c mice results in SCID, as do experimentally induced mutations in RAG1 and RAG2. SCID in horses results from a spontaneous mutation in DNA-PKcs. Two molecular mechanisms account for SCID in dogs. Jack Russell Terriers have a mutation within the DNA-PKcs gene, whereas Cardigan Welsh Corgi and Basset Hound have different defects in the gene encoding the γ chain that is common to the receptors for IL-2, −4, −7, −9, −15, and −21. The location of the mutation within target genes influences the spectrum of diseases observed in affected animals.

Humanized Mice as Preclinical Models in Transplantation

Animal models have been instrumental in our understanding of the mechanisms of rejection and the testing of novel treatment options in the context of transplantation. We have now entered an exciting era with research on humanized mice driving advances in translational studies and in our understanding of the function of human cells in response to pathogens and cancer as well as the recognition of human allogeneic tissues in vivo. In this chapter we provide a historical overview of humanized mouse models of transplantation to date, outlining the distinct strains and share our experiences in the study of human transplantation immunology.

Models for mature T-cell lymphomas--a critical appraisal of experimental systems and their contribution to current T-cell tumorigenic concepts

Mature T-cell lymphomas/leukemias (MTCL) have been understudied lymphoid neoplasms that currently receive growing attention. Our historically rudimentary molecular understanding and dissatisfactory interventional success in this complex and for the most part poor-prognostic group of tumors is only slightly improving. A major limiting aspect in further progress in these rare neoplasms is the lack of suitable model systems that would substantially facilitate pathogenic studies and pre-clinical drug evaluations. Such representations of MTCL have thus far not been systematically appraised. We therefore provide an overview on existing models and point out their particular advantages and limitations in the context of the specific scientific questions. After addressing issues of species-specific differences and classifications, we summarize data on MTCL cell lines of human as well as murine origin, on murine strain predispositions to MTCL, on available models of genetically engineered mice, and on transplant systems. From an in-silico meta-analysis of available primary data of gene expression profiles on human MTCL we cross-reference genes reported to transform T-cells in mice and reflect on their general vs entity-restricted relevance and on target-promoter influences. Overall, we identify the urgent need for new models of higher fidelity to human MTCL with respect to their increasingly recognized diversity and to predictions of drug response.

Transcription factor zinc finger and BTB domain 1 is essential for lymphocyte development

Absent T lymphocytes were unexpectedly found in homozygotes of a transgenic mouse from an unrelated project. T cell development did not progress beyond double-negative stage 1 thymocytes, resulting in a hypocellular, vestigial thymus. B cells were present, but NK cell number and B cell isotype switching were reduced. Transplantation of wild-type hematopoietic cells corrected the defect, which was traced to a deletion involving five contiguous genes at the transgene insertion site on chromosome 12C3. Complementation using bacterial artificial chromosome transgenesis implicated zinc finger BTB-POZ domain protein 1 (Zbtb1) in the immunodeficiency, confirming its role in T cell development and suggesting involvement in B and NK cell differentiation. Targeted disruption of Zbtb1 recapitulated the T(-)B(+)NK(-) SCID phenotype of the original transgenic animal. Knockouts for Zbtb1 had expanded populations of bone marrow hematopoietic stem cells and also multipotent and early lymphoid lineages, suggesting a differentiation bottleneck for common lymphoid progenitors. Expression of mRNA encoding Zbtb1, a predicted transcription repressor, was greatest in hematopoietic stem cells, thymocytes, and pre-B cells, highlighting its essential role in lymphoid development.

Can humanized mice reflect the complex pathobiology of HIV-associated neurocognitive disorders?

There is a rebirth of humanized mouse models in reflecting human immunodeficiency virus (HIV) pathobiology. This has allowed new investigations of viral diversity, immunity and developmental therapeutics. In the past, HIV infection and disease were, in part, mirrored in immune deficient mice reconstituted with human hematopoietic stem cells. What remained from early studies reflected the ability to mirror central nervous system (CNS) disease. As the wide spread use of combination antiretroviral therapies has changed the severity, but not prevalence, of HIV-associated neurocognitive disorders (HAND), mimicking such virus-induced CNS morbidities in humanized animals is essential for HIV/AIDS research activities. To this end, we now review the evidence for how and under what circumstances humanized mice may be utilized for studies of HIV-1 neuropathogenesis.

Key genomic changes necessary for an in vivo lethal mouse marburgvirus variant selection process

Marburgvirus (MARV) infections are generally lethal in humans and nonhuman primates but require in vivo lethal mouse variant selection by the serial transfer (passage) of the nonlethal virus into naïve mice to propagate a lethal infection. The passage of progenitor (wild-type) MARV or Ravn virus (RAVV) from infected scid BALB/c mouse liver homogenates into immunocompetent BALB/c mice results in the selection of lethal mouse viruses from within the quasispecies sufficient to establish lethality in immunocompetent mice. Genomic analysis in conjunction with the passage history of each mutation detailed the altered primary and secondary structures of the viral genomic RNA throughout the process. Key findings included the following: (i) a VP40:D184N mutation previously identified in the lethal guinea pig MARV genome was the first mutation to occur during the passage of both the MARV and RAVV variants; (ii) there was biased hypermutagenesis in the RAVV variant genome; (iii) there were two identical mutations in lethal mouse MARV and RAVV variants, VP40:Y19H in the PPPY motif and VP40:D184N in a loop structure between the two VP40 domains; (iv) the passage of wild-type MARV and RAVV in mice resulted in the selection of viral variants from among the quasispecies with different genotypes than those of the wild-type viruses; and (v) a lethal mouse RAVV variant had different tissue tropisms distinct from those of its wild-type virus. These studies provide insights into how marburgviruses manipulate the host for enzymes, metabolites, translation regulators, and effectors of the innate immune response to serve as potential viral countermeasures.

Murine models of immunodeficiency and autoimmune disease

Genetically determined murine immunodeficiency states are useful for understanding the function of specific immune-system genes and cellpopulations. In addition, certain immunodeficient strains may be exploited as hosts for foreign tumors or immune cells. The more commonly used immunodeficiency models are described in this appendix. Not included are strains better known for primary neurological or neuromuscular abnormalities or for defective osteoclast function. Many of the recently described immune-deficient "knockout" strains are described, including cytokine and cytokine receptor knockout strains. The most widely studied murine strains for autoimmune disease and experimental autoreactivity are also listed.

Mouse models with human immunity and their application in biomedical research

Biomedical research in human beings is largely restricted to in vitro studies that lack complexity of a living organism. To overcome this limitation, humanized mouse models are developed based on immunodeficient characteristics of severe combined immunodeficiency (SCID) or recombination activating gene (Rag)(null) mice, which can accept xenografts. Peripheral constitution of human immunity in SCID or Rag(null) mice has been achieved by transplantation of mature human immune cells, foetal human thymus, bone marrow, liver tissues, lymph nodes or a combination of these, although efficiency needs to be improved. These mouse models with constituted human immunity (defined as humanized mice in the present text) have been widely used to investigate the basic principles of human immunobiology as well as complex pathomechanisms and potential therapies of human diseases. Here, elements of an ideal humanized mouse model are highlighted including genetic and non-genetic modification of recipient mice, transplantation strategies and proposals to improve engraftments. The applications of the humanized mice to study the development and response of human immune cells, human autoimmune diseases, virus infections, transplantation biology and tumour biology are reviewed as well.

Animal models for the study of squamous cell carcinoma of the upper aerodigestive tract: a historical perspective with review of their utility and limitations. Part A. Chemically-induced de novo cancer, syngeneic animal models of HNSCC, animal models of transplanted xenogeneic human tumors

Understanding the complex histological, genetic and molecular changes that lead to malignant transformation of squamous epithelia of the head and neck will likely guide the development of methods for improved diagnosis, monitoring and treatment of head and neck squamous cell carcinoma (HNSCC). The development and use of animal models that closely mimic the histopathology and molecular pathogenesis of HNSCC in humans would greatly expand the research possibilities and provide a means of testing potential therapeutic agents. However, many available animal models of HNSCC fall short of this objective. In order for investigators to select the appropriate model to answer scientific questions, it is important to understand the benefits and limitations of available animal models for the study of HNSCC. The purpose of this work is to give an overview of the most pertinent animal models of HNSCC, and to discuss future directions of research in this field.

T Cells and Cytokines in the Pathogenesis of Acquired Myasthenia Gravis

Although the symptoms of myasthenia gravis (MG) and experimental MG (EAMG) are caused by autoantibodies, CD4(+) T cells specific for the target antigen, the nicotinic acetylcholine receptor, and the cytokines they secrete, have an important role in these diseases. CD4(+) T cells have a pathogenic role, by permitting and facilitating the synthesis of high-affinity anti-AChR antibodies. Th1 CD4(+) cells are especially important because they drive the synthesis of anti-AChR complement-fixing IgG subclasses. Binding of those antibodies to the muscle AChR at the neuromuscular junction will trigger the complement-mediated destruction of the postsynaptic membrane. Thus, IL-12, a crucial cytokine for differentiation of Th1 cells, is necessary for development of EAMG. Th2 cells secrete different cytokines, with different effects on the pathogenesis of EAMG. Among them, IL-10, which is a potent growth and differentiation factor for B cells, facilitates the development of EAMG. In contrast, IL-4 appears to be involved in the differentiation of AChR-specific regulatory CD4(+) T cells, which can prevent the development of EAMG and its progression to a self-maintaining, chronic autoimmune disease. Studies on the AChR-specific CD4(+) cells commonly present in the blood of MG patients support a crucial role of CD4(+) T cells in the development of MG. Circumstantial evidence supports a pathogenic role of IL-10 also in human MG. On the other hand, there is no direct or circumstantial evidence yet indicating a role of IL-4 in the modulatory or immunosuppressive circuits in MG.

Enhancement of natural killer cell function by titanocenes in mice bearing Ehrlich ascites tumour

In the present work, we studied the effects of two titanocenes, biscyclopentadienyldichlorotitanium IV, (DDCT) and its derivative, biscyclopentadienylditiocianatetitanium IV (BCDT), on the activity of natural killer (NK) cells in Ehrlich ascites tumour (EAT)-bearing BALB/c mice. In order to investigate a more direct effect of these compounds on NK cell function, we performed experiments with severe combined immunodeficiency (SCID) mice, which exhibit a normal NK cell response in the absence of T and B cells. The treatment consisted of intraperitoneal (i.p.) administration of 15 mg/kg/day of DDCT for 2 days or 10 mg/kg/day of BCDT for 3 days. In addition, to verify whether the effects produced by the titanocenes were compound specific or related to a direct antitumour effect, we also investigated the effects of a 3-day treatment with 100 mg/kg of cyclophosphamide cyclophosphamide on NK cell activity. Our results demonstrated that, in BALB/c and SCID mice, NK cell function declined to subnormal levels after inoculation of the tumour. In these animals, although treatment with DDCT and BCDT significantly enhanced NK cell function, only DDCT restored NK cell activity to normal values in all stages studied. Conversely, treatment with cyclophosphamide reduced NK cell function in nontumour bearing SCID mice and was also unable to restore the decreased NK activity of tumour-bearing SCID mice, thus demonstrating that the enhancement of NK cell function by titanocenes is compound specific. The same effect of cyclophosphamide was observed with BALB/c mice. In the present study, the up-modulatory effects of these two compounds on NK cell function reveal a new aspect of the mechanism of antitumoural action of titanocenes.

Formation of an active form of the interleukin-2/15 receptor beta-chain by insertion of the intracisternal A particle in a radiation-induced mouse thymic lymphoma and its role in tumorigenesis

Although many reports suggest that aberrant regulation of cytokine signaling pathways via the interleukin-2 receptor (IL-2R) induces tumorigenic transformation, constitutively active IL-2R in tumors has not been reported. We searched for genomic alteration of the IL-2/15R beta-subunit gene (IL-2/15R beta) in cytokine-independent cell lines established from radiation-induced mouse thymic lymphomas. In the TL34 cell line and its primary tumor, one of the IL-2/15R beta alleles was rearranged by the insertion of an intracisternal A particle (IAP) retrotransposon. The IAP-IL2/15R beta chimeric gene expressed chimeric mRNA in which IAP-coding Gag-Pol mRNA was fused to IL-2/15R beta mRNA and coded for Gag-Pol-IL-2/15R beta chimeric protein. Forced expression of the Gag-Pol-IL-2/15R beta chimeric cDNA in a mouse cytotoxic T-cell line (CTLL-2) converted IL-2-dependent cell growth to IL-2-independent growth, suggesting that the chimeric protein activates some of the IL-2 signaling pathways necessary for cell proliferation. Downregulation of the expression of the Gag-Pol-IL-2/15R beta chimeric protein in TL34 by antisense RNA inhibited cell growth, and concomitantly reduced the level of c-myc protein. These results suggest that the Gag-Pol-IL-2/15R beta is a constitutively active form that transmits proliferative signals by expressing downstream target genes, including c-myc. Thus, we demonstrated that the chimeric receptor gene produced by the insertion of an IAP functions as an oncogene by providing IL-2-independent autonomous growth potential.

Immunological disorders and DNA repair

Cellular DNA continuously incurs damage and a range of damage response mechanisms function to maintain genomic integrity in the face of this onslaught. During the development of the immune response, the cell utilises three defined processes, V(D)J recombination, class switch recombination and somatic hypermutation, to create genetic diversity in developing T and B cells. Curiously, the damage response mechanisms employed to maintain genomic stability in somatic cells have been exploited and adapted to help generate diversity during immune development. As a consequence of this overlap, there is mounting evidence that disorders attributable to impaired damage response mechanisms display associated immunodeficiency. Since double strand breaks (DSB) are created during at least two of the mechanisms used to create immunoglobulin diversity, namely V(D)J recombination and class switch recombination, it is not surprising that disorders associated with defects in the response to double strand breaks are those most associated with immunodeficiency. Here, we review the steps involved in the generation of genetic diversity during immune development with a focus on the damage response mechanisms employed and then consider human immunodeficiency disorders associated with impaired damage response mechanisms.

Dimerization, translocation and localization of Ku70 and Ku80 proteins

The Ku protein is a complex of two subunits, Ku70 and Ku80, and was originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. The Ku protein plays a key role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, transcription regulation, and V(D)J recombination. The mechanism underlying the regulation of all the diverse functions of Ku is still unclear, although it seems that Ku is a multifunctional protein that works in nuclei. On the other hand, several studies have reported cytoplasmic or cell surface localization of Ku in various cell types. To clarify the fundamental characteristics of Ku, we have examined the expression, heterodimerization, subcellular localization, chromosome location, and molecular mechanisms of the nuclear transport of Ku70 and Ku80. The mechanism that regulates for nuclear localization of Ku70 and Ku80 appears to play, at least in part, a key role in regulating the physiological function of Ku in vivo.

Gastric hyperplasia and parietal cell loss in Taenia taeniaeformis inoculated immunodeficient mice

Immunodeficient mice were studied to determine their suitability as models in investigating the role of Taenia taeniaeformis larval products in the development of gastric hyperplasia. Recombinant active gene 2 (RAG2)-deficient and severe combined immune-deficient (SCID) mice were studied as candidate animal models. RAG2-deficient mice inoculated orally with T. taeniaeformis eggs developed gastric hyperplasia with alcian blue-periodic acid-Schiff-positive cell proliferation similar to those of rats. SCID mice inoculated with different doses and routes of T. taeniaeformis in vitro-hatched oncospheres and those orally inoculated with eggs resulted also in different degrees of gastric hyperplasia. Influence of inoculation forms of parasite, doses and routes of inoculation on initiation of hyperplastic gastropathy was suggested to be dependent on number and size of developed larvae. Both RAG2-deficient and SCID mice with hyperplastic mucosa were observed with significant loss of parietal cells. Apparent decrease in parietal cell number was observed in SCID mice at 2 weeks after intraperitoneal inoculation with oncospheres before hyperplastic lesions developed. Earliest occurrence of gastric hyperplasia in SCID mice was observed at 3 weeks after oral inoculation of in vitro-hatched oncospheres, sooner than orally inoculated rats. The results suggested that these immunodeficient mice could be used as animal models to study factors involved in T. taeniaeformis-induced gastric mucous cell hyperplasia.

Human-SCID mouse chimeric models for the evaluation of anti-cancer therapies

The ability to engraft human tumors and human immunocompetent cells successfully in severe combined immunodeficient (SCID) mice has spawned the development and use of human-mouse chimeric models to evaluate anti-cancer therapies. The lack of standardization and many other potential pitfalls have contributed to the current controversy surrounding the reliability of these different models. Five frequently used SCID mouse models and their specific applications are summarized with the specific aim of providing an objective discussion of the strengths and limitations of each model, together with suggestions for overcoming some of the variabilities and for improving the design and use of future models.

Cryopreservation of human ovarian tissue

As survival rates for young cancer patients continue to improve, protection against iatrogenic infertility caused by chemotherapy and/or radiotherapy assumes a higher priority. As things stand, women patients have few options to preserve their fertility while children have none at all.

Evaluation of the human choroidal melanoma rabbit model for studying microcirculation patterns with confocal ICG and histology

The aim of this study was to develop consistently focal elevated choroidal masses of human choroidal melanoma in immunosuppressed rabbits and to correlate the visualization of prognostically significant microcirculation patterns from confocal indocyanine green angiography with histologic microcirculation patterns. A human choroidal melanoma cell line (OCM1) was implanted in the choroid of 40 rabbit eyes using three different techniques: transscleral choroidal injection of a cell suspension, injection of a cell suspension in a surgically induced cyclodialysis cleft, and implantation of solid tumor fragments in a surgically induced cyclodialysis cleft. The rabbits were immunosuppressed with daily injections of Cyclosporin A to prevent host versus graft reaction. The eyes were studied weekly with indirect ophthalmoscopy and fundus photography to monitor tumor growth and indocyanine green angiography using a confocal scanning laser ophthalmoscope to identify microcirculation patterns in vivo and correlate these findings with the histologic demonstration of tumor microcirculation patterns. A tumor mass was identified by indirect ophthalmoscopy in 16 of the 40 implanted rabbit eyes (40%). Each of these tumors was confirmed histologically to represent a focal elevated choroidal mass. All 16 elevated choroidal masses grow in eyes in which solid tumor fragments were implanted. In total, a melanoma was identified histologically in 28 of the implanted 40 eyes (70%). In addition to the 16 eyes where the melanoma appeared as a focal elevated choroidal mass, 4 eyes contained a focal elevated mass in the sclera and 8 eyes contained a flat choroidal tumor. Histologically, microcirculation patterns were identified only in the 16 eyes with focal elevated choroidal masses. Confocal indocyanine green angiography imaged microcirculation patterns in 13 of these 16 eyes (81%). The surgical implantation of small solid fragments of human choroidal melanoma in immunosuppressed rabbit eyes provides the best method to consistently obtain focal elevated choroidal masses. These focal elevated choroidal masses resemble booth the localization and the growth pattern of choroidal melanomas in humans. In addition, they also contain microcirculation patterns similar to those seen in humans that are detectable with confocal indocyanine green angiography. The use of indocyanine green angiography with this animal model may be especially useful in designing and evaluating anti-microcirculation treatments directed at uveal melanoma.

Apparent trans-chromosomal antibody class switch in mice bearing an Igh(a) mu-chain transgene on an Igh(b) genetic background

Native high molecular weight dextran induces a thymus-independent response in BALB/c mice. When the dextran epitope is linked to a protein carrier the response becomes thymus-dependent. IgG antibodies produced after secondary immunization had epitope specificity and idiotope of myeloma M104E. The antibody of M104E (mu, lambda1) is representative for antibodies produced by mice with immunoglobulin haplotype Igh(a) in response to immunization with dextran B1355S. Myeloma product and physiological antibodies share specificity for the alpha(1-3) glucosidic linkage and have idiotopes in common. Mice with haplotypes other than Igh(a) (e.g. Igh(b)) are unable to yield this type of response. A complete rearranged immunoglobulin mu-chain gene with a VDJ-region from BALB/c (Igh(a)) myeloma protein M104E had been introduced into the genome of BALB/c congenic mice having the haplotype Igh(b). As was shown previously in our laboratory the M104E mu-chain transgene confers Igh(a)-type reactivity to Igh(b) mice. In experiments described in this report we used the thymus-dependent form of the antigen to immunize mice bearing the M104E mu-chain, either alone or together with the lambda1-chain, as a transgene on an Igh(b) genetic background. Serological analysis revealed a class switch to IgG very similar to that seen in BALB/c mice with respect to magnitude, kinetics, epitope and idiotope specificity. The pattern of IgG subclass expression was indistinguishable in mu-chain transgenic Igh(b) and normal BALB/c mice. The class switch occurred even though, as is shown here, the transgene had become incorporated in a site not linked to the Igh locus on chromosome 12. We propose a model for this apparent trans-chromosomal class switch recombination which is based on mechanisms known for conventional switch recombination.

Extrathymic T Cell Differentiation in the Human Intestine Early in Life

It is clear from experimental studies in mice that T cell maturation can occur outside the thymus, especially in the intestine. There is little sound evidence so far that extrathymic T cell maturation occurs to any significant extent in human gut, and, postnatally, there is abundant evidence that the gut mucosa is an immune effector organ. Here, we describe a large population of T lymphocytes in human fetal intestinal mucosa that are proliferating (Ki67+) in the absence of foreign Ag (CD3+, Ki67+ lamina propria lymphocytes (LPL) 22 ± 1.8% and CD3+, Ki67+ intraepithelial lymphocytes (IEL) 9.1 ± 1.4%), that express the T cell activation markers CD103, HLA-DR, and L-selectinlow, and that express mRNA transcripts for pre-TCR-α. There is also a substantial proportion of CD7+ LPLs that do not express CD3 (CD3−7+, 14 ± 7% of all LPLs) in the fetal gut that may be differentiating into CD3+ cells. Rearranged TCR-β transcripts of fetal LPLs, IELs, and paired blood lymphocytes were cloned and sequenced, and virtually no overlap of clonality was observed between blood and intestine, suggesting that gut T cells may not be derived from the blood. In addition, 30 days after engraftment of SCID mice with fetal intestine, CD3−7+ cells, proliferating T cells, and pre-TCR-α transcripts were abundant, and there is a threefold increase in CD3+ IELs. These data show that in the human intestine before birth a population of precursor T cells exists that may be differentiating into mature T cells in situ

SCID mouse models of human stem cell engraftment

The discovery of the severe combined immunodeficiency (scid) mouse mutation has provided a tool for establishment of small animal models as hosts for the in vivo analysis of normal and malignant human pluripotent hemopoietic stem cells. Intravenous injection of irradiated scid mice with human bone marrow, cord blood, or G-CSF cytokine-mobilized peripheral blood mononuclear cells, all rich in human hemopoietic stem cell activity, results in the engraftment of a human hemopoietic system in the murine recipient. This model has been used to identify a pluripotent stem cell, termed "scid-repopulating cell" (SRC) that is more primitive than any of the hemopoietic stem cell populations identified using the currently available in vitro methodology. In this review, we describe the development and use of this model system, termed Hu-SRC-SCID, and summarize the discoveries that have resulted from the investigation of human stem cells in this model. Finally, we detail the recent extension of the original Hu-SRC-SCID model system based on the C.B-17-scid mouse as the murine host to the Hu-SRC-NOD-SCID model based on the NOD-scid mouse as the host. The engraftment of human stem cells in the Hu-SRC-NOD-SCID model is enhanced over that observed in the Hu-SRC-SCID model and results in exceptionally high levels of human hemopoietic cells in the murine recipient. Future directions to further improve the Hu-SRC-NOD-SCID model system and the potential utility of this model in the preclinical and diagnostic arenas of hematology and oncology are discussed.

Interleukin-4 and interleukin-10 are chondroprotective and decrease mononuclear cell recruitment in human rheumatoid synovium in vivo

We used the severe combined immunodeficient (SCID) mouse model to assess the effect of interleukin-4 (IL-4) or IL-10 injection on cartilage degradation and mononuclear cell (MNC) recruitment to human rheumatoid synovium in vivo. Human rheumatoid synovium and cartilage from five rheumatoid arthritis patients, obtained after joint replacement surgery, were engrafted subcutaneously to 6-8-week-old SCID CB17 mice. Synovial tissues were injected with recombinant human IL-4 (rhIL-4, 100 ng; rhIL-10, 100 ng), both cytokines, or tumour necrosis factor-alpha (TNF-alpha) (1000 U), or phosphate-buffered saline twice a week for 4 weeks. The graft was removed and immunochemical analysis was carried out to assess intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin expression. Moreover, cartilage degradation was assessed through the quantification of the erosion surface on a computerized image of the engrafted cartilage at high power view. MNC recruitment in the synovial tissue was determined by labelling blood MNC with indium-111 before their intraperitoneal injection. The activity obtained in the region of the graft were determined with a gamma camera 72 hr postinjection. The results are expressed as a percentage of initial injected activity. After 4 weeks we observed a decrease of cartilage area in controls (77 +/- 8%), inhibited after injection of IL-4, IL-10, or both cytokines (90 +/- 3%, 89.1 +/- 4%, 89.2 +/- 5% respectively), and 57 +/- 17% after TNF-alpha injection. The % MNC activity in the graft decreased to 77 +/- 81% (NS), 9 +/- 4% (P < 0.003) and 19 +/- 6% (P < 0.007) compared with untreated synovial tissue after treatment with IL-4, IL-10, or both cytokines, respectively. Moreover, IL-10 but not IL-4 decreased the expression of ICAM-1 but not VCAM-1 or E-selectin by synovial cells. These results suggest that IL-10 and IL-4 could have chondroprotective properties, and that IL-10 but not IL-4 inhibits MNC traffic towards the synovial tissue efficiently.

High-resolution recombinational map of mouse chromosome 16

Five intersubspecific backcrosses and an intercross were used to establish a sex-averaged recombinational map spanning 56 cM across most of mouse Chromosome 16 (Chr 16). A total of 123 markers were ordered using an interval mapping approach to identify 425 recombination sites in a collection of 1154 meioses from 1155 progeny generated in the six crosses. The markers include the 10 "classic" Chr 16 reference markers, 26 additional genes or transcripts including two phenotypic markers (Pit1dw and Kcnj6wv), and 87 simple sequence length polymorphisms (SSLPs). One set of monozygotic twins was detected among the 304 meioses mapped to highest resolution. The reference markers and SSLPs allow the map to be well integrated with existing maps of Chr 16. The average distance between crossover sites is less than 500 kb for most chromosomes, making this collection of recombinant chromosomes useful as a binning and ordering resource for YAC-based physical map assembly on Chr 16.

Nonsense mutation at Tyr-4046 in the DNA-dependent protein kinase catalytic subunit of severe combined immune deficiency mice

The severe combined immune deficiency (SCID) mouse was reported as an animal model for human immune deficiency. Through the course of several studies, the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) gene came to be considered a candidate for the SCID-responsible gene. We isolated an ORF of the murine DNA-PKcs gene from SCID mice and their parent strain C.B-17 mice and determined the DNA sequences. The ORF of the murine DNA-PKcs gene contained 4128-aa residues and had 78.9% homology with the human DNA-PKcs gene. A particularly important finding is that a T to A transversion results in the substitution of termination codon in SCID mice for the Tyr-4046 in C.B-17 mice. No other mutation was detected in the ORF of the gene. The generality of this transversion was confirmed using four individual SCID and wild-type mice. The substitution took place in the phosphatidylinositol 3-kinase domain, and the mutated gene encodes the truncated products missing 83 residues of wild-type DNA-PKcs products. Furthermore, the quantity of DNA-PKcs transcript in wild-type and SCID cells was almost equal. These observations indicate that the DNA-PKcs gene is the SCID-responsible gene itself and that the detected mutation leads to the SCID aberration.

Identification of a nonsense mutation in the carboxyl-terminal region of DNA-dependent protein kinase catalytic subunit in the scid mouse

DNA-dependent protein kinase (DNA-PK) consists of a heterodimeric protein (Ku) and a large catalytic subunit (DNA-PKcs). The Ku protein has double-stranded DNA end-binding activity that serves to recruit the complex to DNA ends. Despite having serine/threonine protein kinase activity, DNA-PKcs falls into the phosphatidylinositol 3-kinase superfamily. DNA-PK functions in DNA double-strand break repair and V(D)J recombination, and recent evidence has shown that mouse scid cells are defective in DNA-PKcs. In this study we have cloned the cDNA for the carboxyl-terminal region of DNA-PKcs in rodent cells and identified the existence of two differently spliced products in human cells. We show that DNA-PKcs maps to the same chromosomal region as the mouse scid gene. scid cells contain approximately wild-type levels of DNA-PKcs transcripts, whereas the V-3 cell line, which is also defective in DNA-PKcs, contains very reduced transcript levels. Sequence comparison of the carboxyl-terminal region of scid and wild-type mouse cells enabled us to identify a nonsense mutation within a highly conserved region of the gene in mouse scid cells. This represents a strong candidate for the inactivating mutation in DNA-PKcs in the scid mouse.

Effect of the mouse scid mutation on meiotic recombination

The goal of this study was to determine the effect of the mouse severe combined immunodeficiency (scid) mutation on the rate of meiotic recombination, by standard backcross linkage analysis. For this purpose, we examined four crosses that involved F1 hybrid animals heterozygous for the strain C57BL/6 and BALB/c genomes. In one set of reciprocal crosses, F1 animals were homozygous scid/scid, and in a second set of reciprocal crosses, F1 mice were homozygous wild-type (+/+) at the scid locus. Backcross progeny were typed for recombination between selected genetic markers on mouse Chromosomes (Chrs) 1, 4, 6, 7, 9, 15, and 17. Although some differences in recombination were observed over some intervals, the expression of the SCID phenotype did not appear to have a major or consistent effect on meiotic recombination.

Cutting apart V(D)J recombination

The past year has seen major advances in our understanding of the recombination mechanism by which antibody and T cell receptor genes are assembled during lymphoid development. The initial cleavage events can be carried out in vitro by purified RAG1 and RAG/ protein. In addition, a number of genes involved in later steps of the reaction have been cloned, opening the way for an in-depth biochemical analysis of this critical developmental process.

Immune deficiency in SCID mice

Since the discovery of SCID mice in 1983, numerous studies utilizing these mice were carried out. These investigations can be classified into two major groups. First, the analysis of the immune defect has revealed defective V(D)J recombination and defective DNA double-strand break repair, and has lead to the identification of the candidate gene for SCID mice. Second, the use of SCID mice to explore ways to introduce a murine or xenogeneic immune system into SCID mice by taking advantage of the immune deficiency of the mice has provided an animal model to examine the in vivo function of transferred human or murine immune cells. In this review, we summarize the recent advances made in these two areas of SCID mouse research.

The use of SCID mice in biotechnology and as a model for human disease

The use of SCID (severe combined immunodeficient) mice in medical research and biotechnology has increased tremendously in recent years. This review outlines the major characteristics of these animals and the impediments that they pose to the engraftment of human cells and tissues. The development of our SCID mice pretreatment protocol (anti-asialo GM1 antisera and radiation) is described, and the results of xenotransplantation studies of human cells and tissues in these pretreated animals are outlined. Wherever possible, data from transplantation studies (of human tissues and cells) in pretreated and nonpretreated animals are compared. The potential of our pretreated SCID mice for medical research and biotechnology is discussed.

Gene for the catalytic subunit of mouse DNA-dependent protein kinase maps to the scid locus

The gene encoding the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) has been proposed recently as a candidate gene for the mouse severe combined immune deficiency (scid) locus. We have used a partial cDNA clone for human DNA-PKcs to map the mouse homologue using a large interspecific backcross panel. We found that the mouse gene for DNA-PKcs does not recombine with scid, consistent with the hypothesis that scid is a mutation in the mouse gene for DNA-PKcs.

X-ray induced translocations in bone marrow cells of scid and wild type mice detected by fluorescence in situ hybridization using mouse chromosome specific DNA libraries

Radiation induced chromosomal aberrations in bone marrow cells of scid and normal mice were studied at different sampling times. Fluorescence in situ hybridization (FISH) with DNA libraries specific for chromosomes 1, 11 and 13 was applied to identify the stable types of chromosomal aberrations in addition to the unstable ones. The results obtained confirm earlier observations on stem cell spermatogonia in that, contrary to the situation in normal mice, only very low levels of translocations could be recovered from scid mice at relatively long sampling times (3 weeks). However, studies at a 24 h sampling period demonstrated substantial induction of translocations in scid mice. This suggests enhanced elimination of translocation carrying cells in scid mice during successive cell proliferation, possibly via falling apart of the translocation at the original points of exchange or due to lethal damage at the translocation break points.

TH1 cells trigger tumor necrosis factor alpha-mediated hypersensitivity to Pseudomonas aeruginosa after adoptive transfer into SCID mice

Recent experiments have shown that gamma interferon (IFN-gamma), either administered or induced in vivo, e.g., by certain bacteria, is a key mediator in inducing hypersensitivity to bacterial lipopolysaccharides. The source of endogenous IFN-gamma in this context (natural killer versus TH1 cells) has not been investigated yet. In order to investigate the role of antigen-specific, IFN-gamma-producing TH1 cells in murine Pseudomonas aeruginosa infection, a murine TH1 cell line was propagated in vitro by using recombinant P. aeruginosa outer membrane protein I. Adoptive transfer experiments were performed by intravenous injection of various amounts of TH1 cells into P. aeruginosa-challenged SCID mice. Adoptive transfer of 5 x 10(6) T cells into SCID mice followed by an intraperitoneal challenge with 1.4 x 10(6) CFU of live P. aeruginosa resulted in the rapid death of the animals within 12 h postchallenge, whereas transfer of lower T-cell doses and saline as a control did not cause any detrimental effects. After challenge with 2.8 x 10(6) CFU of P. aeruginosa, similar results were obtained 18 h postchallenge; however, at the end of the 72-h observation period, no significant differences in survival rates were obtained between the groups treated with different amounts of T cells. The rapid death of mice treated with 5 x 10(6) T cells was reflected by 860-fold-elevated levels of tumor necrosis factor alpha (TNF-alpha) present in serum 2 h postchallenge, whereas no significant differences in TNF-alpha serum levels were detectable in mice treated with lower doses of T cells or with saline. Pretreatment of T-cell-reconstituted SCID mice with neutralizing anti-IFN-gamma monoclonal antibodies completely protected mice from bacterial challenge and reduced TNF-alpha levels in serum. We conclude that under the experimental conditions described here, IFN-gamma- and interleukin-2-producing TH1 cells represent an important trigger mechanism inducing TNF-alpha-mediated hypersensitivity to bacterial endotoxin.

DNA-dependent kinase (p350) as a candidate gene for the murine SCID defect

Severe combined immunodeficient (SCID) mice are deficient in a recombination process utilized in both DNA double-strand break repair and in V(D)J recombination. The phenotype of these mice involves both cellular hypersensitivity to ionizing radiation and a lack of B and T cell immunity. The catalytic subunit of DNA-dependent protein kinase, p350, was identified as a strong candidate for the murine gene SCID. Both p350 and a gene complementing the SCID defect colocalize to human chromosome 8q11. Chromosomal fragments expressing p350 complement the SCID phenotype, and p350 protein levels are greatly reduced in cells derived from SCID mice compared to cells from wild-type mice.

Complementation of V(D)J recombination defect and X-ray sensitivity of scid mouse cells by human chromosome 8

Cells derived from mice homozygous for the severe combined immune deficiency (scid) mutation exhibit hypersensitivity to ionizing radiation, and defects in DNA double-strand break repair and V(D)J recombination. Using the technique of microcell-mediated chromosome transfer, we have introduced a number of dominantly marked human chromosomes into scid cells to localize the human homolog of the murine scid gene. Analysis of human-scid hybrid clones revealed that the presence of human chromosome 8 partially restored accurate V(D)J recombination and radioresistance to scid cells. Subsequent loss of the human chromosome 8 from human-scid hybrid clones rendered these cells sensitive to gamma-radiation and impaired their ability to catalyse V(D)J recombination. Introduction of chromosomes 2, 14, 16 and 19 that encode other repair genes did not result in the correction of these two scid defects. These observations demonstrate that the human homolog of the mouse scid gene resides on human chromosome 8.

Rch1, a protein that specifically interacts with the RAG-1 recombination-activating protein

RAG1 and RAG2 are lymphoid-specific genes that together induce V(D)J recombinase activity in a variety of nonlymphoid cell types. While no other lymphoid-specific factors are required to induce recombination, other factors with more widespread expression patterns have been implicated in the reaction. However, none of these factors have been cloned, and their relationship to the RAG proteins is unclear. Using the yeast two-hybrid assay, we have identified RCH1, a gene encoding a protein of molecular weight 58,000 that interacts specifically with RAG-1. The predicted Rch1 protein sequence is 47% identical to yeast SRP1, a protein associated with the nuclear envelope. A truncated form of Rch1, which retains the ability to interact with RAG-1, reduces V(D)J recombination activity in HeLa cells.

Autoimmunity versus allo- and xeno-reactivity in SCID mice

The ability of SCID mice to accept xenografts has been exploited to study the survival, function and potential of peripheral blood mononuclear cells (PBMC) from patients with autoimmune disorders to produce tissue injury in the mouse. Studies performed with PBMC obtained from patients with organ specific and multisystem autoimmune diseases indicate that human PBMC survive in SCID mice for several months, produce IgG and autoantibodies with the same specificities as are found in the donor. Tissue injury is not generally observed in the SCID mouse recipient. SCID mice have also been partially reconstituted with bone marrow from BB (diabetic) and MRL (lupus) mice. SCID mice injected with both spleen cells from mice with collagen induced arthritis together with native bovine collagen developed more severe arthritis than the donors. SCID mice have therefore proven to be a useful resource to study autoimmunity. In both xeno- and allografts of mature lymphocytes, graft versus host reactions occur. Further studies will be necessary to improve donor cell survival without aggravating graft versus host disease.

SCID mice as models for parasitic infections

Mice with severe combined immunodeficiency (SCID mice) have become a favored model system for the study of many parasitic diseases. In this review, Samuel Stanley Jr and Herbert Virgin IV provide a brief overview of the biology of the SCID mouse, and review some examples of how the SCID mouse model has been applied to the study of the immunology of a number of different parasitic diseases.

The scid mutation in mice causes defects in the repair system for both double-strand DNA breaks and DNA cross-links

The sensitivity of scid fibroblasts established from C.B17-scid/scid fetuses to the DNA-damaging agents bleomycin, neocarzinostatin, mechlorethamine, mitomycin C, methyl methanesulfonate, and ultraviolet light, all of which induce different types of DNA damage, was examined. Scid fibroblasts were 2.8-, 3.7-, and 3.0-fold more sensitive to bleomycin, neocarzinostatin, and mechlorethamine, respectively, than wild-type fibroblasts derived from C.B17-+/+ fetuses. These findings indicate that the scid mutation in mice causes defects in repairing both double-strand DNA breaks and DNA cross-links.

Murine scid cells complement ataxia-telangiectasia cells and show a normal post-irradiation response of DNA synthesis

The murine severe combined immunodeficient mutation (scid) is characterized by a lack of both B and T cells, due to a defect in lymphoid variable-(diversity)-joining (V(D)J) rearrangement. Scid cells are highly sensitive to both radiation-induced killing and chromosomal aberrations. Significantly reduced D0 and n values were demonstrated in scid cells and were similar to ataxia-telangiectasia (AT) cells (a unique human disease conferring whole body radiosensitivity). However, the kinetics of DNA synthesis after irradiation were different between the two cell types. In contrast with the radioresistant DNA synthesis of AT cells, DNA synthesis of scid cells was markedly inhibited after irradiation. The existence of different mutations was also supported by evidence of complementation in somatic cell hybrids between scid cells and AT cells. Our results indicate that the radiobiological character of scid is similar to AT but is presumably caused by different mechanisms.