Mutations in mice that influence natural killer (NK) cell activity

Strategies to enhance NK cell function for the treatment of tumors and infections

Natural killer (NK) cells are innate immune cells equipped with the ability to rapidly kill stressed cells that are neoplastic or virally infected. These cells are especially important in settings where these stressed cells downregulate MHC class I molecules and evade recognition by cytotoxic T cells. However, the activity of NK cells alone is often suboptimal to fully control tumor growth or to clear viral infections. Thus, the enhancement of NK cell function is necessary to fully harness their antitumor or antiviral potential. In this review, we discuss how NK cell function can be augmented by the modulation of signal transduction pathways, by the manipulation of inhibitory/activating receptors on NK cells, and by cytokine-induced activation. We also discuss how some of these strategies are currently impacting NK cells in the treatment of cancer and infections.

Biological Characteristics of Severe Combined Immunodeficient Mice Produced by CRISPR/Cas9-Mediated Rag2 and IL2rg Mutation

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas)9 is a novel and convenient gene editing system that can be used to construct genetically modified animals. Recombination activating gene 2 (Rag2) is a core component that is involved in the initiation of V(D)J recombination during T- and B-cells maturation. Separately, the interleukin-2 receptor gamma chain gene (IL2rg) encoded the protein-regulated activity of natural killer (NK) cells and shared common receptors of some cytokines. Rag2 and IL2rg mutations cause immune system disorders associated with T-, B-, and NK cell function and some cytokine activities. In the present study, 2 single-guide RNAs (sgRNAs) targeted on Rag2 and IL2rg genes were microinjected into the zygotes of BALB/c mice with Cas9 messenger RNA (mRNA) to create Rag2/IL2rg^-/- double knockout mice, and the biological characteristics of the mutated mice were subsequently analyzed. The results showed that CRISPR/Cas9-induced indel mutation displaced the frameshift of Rag2 and IL2rg genes, resulting in a decrease in the number of T-, B-, and NK cells and the destruction of immune-related tissues like the thymus and spleen. Mycobacterium tuberculosis 85B antigen could not induce cellular and humoral immune response in mice. However, this aberrant immune activity compromised the growth of several tumor heterogenous grafts in the mutated mice, including orthotopic and subcutaneous transplantation tumors. Thus, Rag2/IL2rg^-/- knockout mice possessed features of severe combined immunodeficiency (SCID), which is an ideal model for human xenograft.

Development of Fetal Sheep Pancreas after Transplantation into Athymic Mice

The capacity of the fetal sheep pancreas to grow and function when transplanted into athymic mice was examined to determine whether this source of tissue might be of potential use in reversing diabetes. For this purpose fetal sheep pancreases were obtained in the period between 50 days of gestation and fullterm (148 days). Explants (1 mm3) in organ culture secreted insulin for at least 7 days, but in steadily diminishing amounts. Acute exposure to arginine (10 mM) and theophylline (10 mM), but not glucose (20 mM), calcium chloride (10 mM), and sodium butyrate (10 mM), caused acute secretion of insulin. Explants survived for many months when grafted beneath the renal capsule of athymic mice, but their growth was less, the epithelial-like component smaller, and the percentage of endocrine cells (31 ± 5%) fewer than the case of transplanted fetal human pancreas. The β cell was the predominant endocrine cell in the ungrafted fetal sheep pancreas. In the transplanted fetal sheep pancreas this was not so, the α and PP cells being dominant—β:α:S:PP = 3:14:3:11. This pattern was unchanged when the recipient mice were hyperglycemic—β:α:δ:PP = 4:13:4:28, with no reduction of blood glucose levels being observed for up to 4 mo after transplantation. Altering the site of transplantation to the spleen or liver did not improve survival of the endocrine cells. Fetal sheep pancreatic explants when transplanted into athymic rats failed to survive. Thus, although the unusual pattern of endocrine differentiation in fetal sheep pancreas transplanted into athymic mice makes it an interesting model for further studies of fetal development, it is not of benefit in normalizing the blood glucose levels of the recipients.

Production and Characterization of Fetal Sheep Pancreatic Islet-Like Cell Clusters

Explants of fetal sheep pancreas transplanted into diabetic athymic mice survive for many months but there is only partial differentiation of the endocrine cells. As an alternative form of graft we examined the possibility of creating islet-like cell clusters (ICCs) by collagenase digestion of the fetal sheep pancreas, as has been described for human and porcine fetal pancreas. Such ICCs did form at the rate of 6-23 per 10 mg pancreas; their size varied between 65 and 474 μm (median 232 μm) and their insulin content was 1.6 ± 0.2 mU per 20 ICCs. Laser scanning confocal analysis showed that 4.6 ± 0.7% of the cells contained insulin. Insulin was secreted from ICCs maintained in culture at the daily rate of 2.5 mU per 30 ICCs. Arginine but not glucose or theophylline enhanced acute insulin secretion in vitro. Transplantation of up to 1000 ICCs into athymic and scid mice resulted in sparse growth of the epithelial-like cells in the graft and only partial differentiation of the endocrine cells. Hyperglycaemia in diabetic recipients was not normalized. Thus, while functioning ICCs can be created from fetal sheep pancreas, they do not appear to be appropriate for transplantation to reverse diabetes in mice.

Regulation of nasal airway homeostasis and inflammation in mice by SHP-1 and Th2/Th1 signaling pathways

Allergic rhinitis is a chronic inflammatory disease orchestrated by Th2 lymphocytes. Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 is known to be a negative regulator in the IL-4α/STAT-6 signaling pathway of the lung. However, the role of SHP-1 enzyme and its functional relationship with Th2 and Th1 cytokines are not known in the nasal airway. In this study, we aimed to study the nasal inflammation as a result of SHP-1 deficiency in viable motheaten (mev) mice and to investigate the molecular mechanisms involved. Cytology, histology, and expression of cytokines and chemokines were analyzed to define the nature of the nasal inflammation. Targeted gene depletion of Th1 (IFN-γ) and Th2 (IL-4 and IL-13) cytokines was used to identify the critical pathways involved. Matrix metalloproteinases (MMPs) were studied to demonstrate the clearance mechanism of recruited inflammatory cells into the nasal airway. We showed here that mev mice had a spontaneous allergic rhinitis-like inflammation with eosinophilia, mucus metaplasia, up-regulation of Th2 cytokines (IL-4 and IL-13), chemokines (eotaxin), and MMPs. All of these inflammatory mediators were clearly counter-regulated by Th2 and Th1 cytokines. Deletion of IFN-γ gene induced a strong Th2-skewed inflammation with transepithelial migration of the inflammatory cells. These findings suggest that SHP-1 enzyme and Th2/Th1 paradigm may play a critical role in the maintenance of nasal immune homeostasis and in the regulation of allergic rhinitis.

The Rag2⁻Il2rb⁻Dmd⁻ mouse: a novel dystrophic and immunodeficient model to assess innovating therapeutic strategies for muscular dystrophies

The development of innovative therapeutic strategies for muscular dystrophies, particularly cell-based approaches, is still a developing field. Although positive results have been obtained in animal models, they have rarely been confirmed in patients and resulted in very limited clinical improvements, suggesting some specificity in humans. These findings emphasized the need for an appropriate animal model (i.e., immunodeficient and dystrophic) to investigate in vivo the behavior of transplanted human myogenic stem cells. We report a new model, the Rag2(-)Il2rb(-)Dmd(-) mouse, which lacks T, B, and NK cells, and also carries a mutant Dmd allele that prevents the production of any dystrophin isoform. The dystrophic features of this new model are comparable with those of the classically used mdx mouse, but with the total absence of any revertant dystrophin positive fiber. We show that Rag2(-)Il2rb(-)Dmd(-) mice allow long-term xenografts of human myogenic cells. Altogether, our findings indicate that the Rag2(-)Il2rb(-)Dmd(-) mouse represents an ideal model to gain further insights into the behavior of human myogenic stem cells in a dystrophic context, and can be used to assess innovative therapeutic strategies for muscular dystrophies.

The risk of hemophagocytic lymphohistiocytosis in Hermansky-Pudlak syndrome type 2

Genetic disorders of lymphocyte cytotoxicity predispose patients to hemophagocytic lymphohistiocytosis (HLH). Reduced lymphocyte cytotoxicity has been demonstrated in Hermansky-Pudlak syndrome type 2 (HPS2), but only a single patient was reported who developed HLH. Because that patient also carried a potentially contributing heterozygous RAB27A mutation, the risk for HLH in HPS2 remains unclear. We analyzed susceptibility to HLH in the pearl mouse model of HPS2. After infection with lymphocytic choriomeningitis virus, pearl mice developed all key features of HLH, linked to impaired virus control caused by a moderate defect in CTL cytotoxicity in vivo. However, in contrast to perforin-deficient mice, the disease was transient, and all mice fully recovered and controlled the infection. An additional heterozygous Rab27a mutation did not aggravate the cytotoxicity defect or disease parameters. In the largest survey of 22 HPS2 patients covering 234 patient years, we identified only 1 additional patient with HLH and 2 with incomplete transient HLH-like episodes, although cytotoxicity or degranulation was impaired in all 16 patients tested. HPS2 confers a risk for HLH that is lower than in Griscelli or Chediak-Higashi syndrome, probably because of a milder defect in cytotoxicity. Preemptive hematopoietic stem cell transplantation does not appear justified in HPS2.

Current advances in cell therapy strategies for muscular dystrophies

INTRODUCTION

Muscular dystrophies are a heterogeneous group of genetic diseases characterized by muscle weakness, wasting and degeneration. Cell therapy consists of delivering myogenic precursor cells to damaged tissue for the complementation of missing proteins and/or the regeneration of new muscle fibres.

AREAS COVERED

We focus on human candidate cells described so far (myoblasts, mesoangioblasts, pericytes, myoendothelial cells, CD133(+) cells, aldehyde-dehydrogenase-positive cells, mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells), gene-based strategies developed to modify cells prior to injection, animal models (dystrophic and/or immunodeficient) used for pre-clinical studies, and clinical trials that have been performed using cell therapy strategies. The approaches are reviewed in terms of feasibility, hurdles, potential solutions and/or research areas from where the solution may come and potential application in terms of types of dystrophies and targets.

EXPERT OPINION

Cell therapy for muscular dystrophies should be put in the context of which dystrophy or muscle group is targeted, what tools are available at hand, but even more importantly what can cell therapy bring as compared with and/or in combination with other therapeutic strategies. The solution will probably be the right dosage of these combinations adapted to each dystrophy, or even to each type of mutation within a dystrophy.

SHP-1 deficient mast cells are hyperresponsive to stimulation and critical in initiating allergic inflammation in the lung

Phosphatase Src homology region 2 domain-containing phosphatase 1 (SHP-1)-deficient mice display an allergic asthma phenotype that is largely IL-13 and STAT6 dependent. The cell types responsible for the Th2 phenotype have not been identified. We hypothesized that SHP-1 deficiency leads to mast cell dysregulation and increased production and release of mediators and Th2 cytokines, leading to the allergic asthma phenotype. We examined SHP-1 regulation of mast cell differentiation, survival, and functional responses to stimulation using bone marrow-derived mast cells from viable motheaten (mev) mice. We assessed pulmonary phenotypical changes in mev mice on the mast cell-deficient Kit(W-Sh) genetic background. The results showed that SHP-1 deficiency led to increased differentiation and survival, but reduced proliferation, of mast cells. SHP-1-deficient mast cells produced and released increased amounts of mediators and Th2 cytokines IL-4 and -13 spontaneously and in response to H(2)O(2), LPS, and Fc epsilonI cross-linking, involving c-Kit-dependent and -independent processes. The Fc epsilonRI signaling led to binding of SHP-1 to linker for activation of T cells 2 and enhanced linker for activation of T cells 2 phosphorylation in mev bone marrow-derived mast cells. Furthermore, the number of mast cells in the lung tissue of mev mice was increased and mast cell production and release of Th2 cytokines were distinctly increased upon Fc epsilonRI stimulation. When backcrossed to the Kit(W-Sh) background, mev mice had markedly reduced pulmonary inflammation and Th2 cytokine production. These findings demonstrate that SHP-1 is a critical regulator of mast cell development and function and that SHP-1-deficient mast cells are able to produce increased Th2 cytokines and initiate allergic inflammatory responses in the lung.

T-cell infiltration and signaling in the adult dorsal spinal cord is a major contributor to neuropathic pain-like hypersensitivity

Partial peripheral nerve injury in adult rats results in neuropathic pain-like hypersensitivity, while that in neonatal rats does not, a phenomenon also observed in humans. We therefore compared gene expression profiles in the dorsal horn of adult and neonatal rats in response to the spared nerve injury (SNI) model of peripheral neuropathic pain. The 148 differentially regulated genes in adult, but not young, rat spinal cords indicate a greater microglial and T-cell response in adult than in young animals. T-cells show a large infiltration in the adult dorsal horn but not in the neonate after SNI. T-cell-deficient Rag1-null adult mice develop less neuropathic mechanical allodynia than controls, and central expression of cytokines involved in T-cell signaling exhibits large relative differences between young and adult animals after SNI. One such cytokine, interferon-gamma (IFNgamma), is upregulated in the dorsal horn after nerve injury in the adult but not neonate, and we show that IFNgamma signaling is required for full expression of adult neuropathic hypersensitivity. These data reveal that T-cell infiltration and activation in the dorsal horn of the spinal cord following peripheral nerve injury contribute to the evolution of neuropathic pain-like hypersensitivity. The neuroimmune interaction following peripheral nerve injury has therefore a substantial adaptive immune component, which is absent or suppressed in the young CNS.

MHC variant peptide-mediated anergy of encephalitogenic T cells requires SHP-1

Our lab has demonstrated that encephalitogenic T cells can be effectively anergized by treatment with MHC variant peptides, which are analogues of immunogenic peptides containing an amino acid substitution at an MHC anchor residue. The MHC variant peptide of myelin oligodendrocyte glycoprotein (MOG)(35-55) proves an effective treatment as it does not induce symptoms of experimental autoimmune encephalomyelitis and fails to recruit macrophages or MOG(35-55)-specific T cells to the CNS. In this study, we sought to characterize the signaling pathways required for the induction of anergy by building upon the observations identifying the tyrosine phosphatase SHP-1 as a critical regulator of T cell responsiveness. Motheaten viable heterozygous mice, which contain a mutation in the SHP-1 gene resulting in a reduction in functional SHP-1, were challenged with MOG(35-55) or the MOG(35-55) MHC variant 45D. These mice display symptoms of experimental autoimmune encephalomyelitis upon immunization with MHC variant peptide and have significant CNS infiltration of tetramer-positive CD4(+) cells and macrophages, unlike B6 mice challenged with the variant peptide. The effects of SHP-1 are directly on the T cell as Motheaten viable heterozygous mice autoreactive T cells are not anergized in vitro. Lastly, we demonstrate no distinguishable difference in the initial interaction between the TCR and agonist or MHC variant. Rather, an unstable interaction between peptide and MHC attenuates the T cell response, seen in a decreased half-life relative to MOG(35-55). These results identify SHP-1 as a mediator of T cell anergy induced by destabilized peptide:MHC complexes.

A critical role of SHP-1 in regulation of type 2 inflammation in the lung

Asthma is a chronic inflammatory disorder of the airways. Type 2 T helper (Th) cell-dominated inflammation in the lung is a hallmark of asthma. Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 is a negative regulator in the signaling pathways of many growth factor and cytokine receptors. However, a direct role of SHP-1 in the IL-4/IL-13 signaling pathway has not been established. In this study, we sought to define the function of SHP-1 in the lung by characterizing the pulmonary inflammation of viable motheaten (mev) mice, and to investigate the molecular mechanisms involved. Pulmonary histology, physiology, and cytokine expression of mev mice were analyzed to define the nature of the inflammation, and the gene-deletion approach was used to identify critical molecules involved. In mev mice, we observed spontaneous Th2-like inflammatory responses in the lung, including eosinophilia, mucus metaplasia, airway epithelial hypertrophy, pulmonary fibrosis, and increased airway resistance and airway hyperresponsiveness. The pulmonary phenotype was accompanied by up-regulation of Th2 cytokines and chemokines. Selective deletion of IL-13 or signal transducer and activator of transcription 6, key genes in the Th2 signaling pathway, significantly reduced, but did not completely eliminate, the inflammation in the lung. These findings suggest that SHP-1 plays a critical role in regulating the IL-4/IL-13 signaling pathway and in maintaining lung homeostasis.

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.

Decreased expression of Src homology 2 domain-containing protein tyrosine phosphatase 1 reduces T cell activation threshold but not the severity of experimental autoimmune myasthenia gravis

Myasthenia gravis (MG) and its murine model experimental autoimmune myasthenia gravis (EAMG) are T cell-dependent, antibody-mediated autoimmune diseases. Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) is a cytosolic tyrosine phosphatase that is involved in regulating the T cell activation cascade from signals initiated through the TCR. To study the role of SHP-1 in EAMG pathogenesis, we immunized C57BL/6 (B6) mice heterozygous for deletion of the SHP-1 gene (me(v+/-)) and their littermate wild type B6 mice with torpedo acetylcholine receptor (TAChR). T cell proliferation and IFNgamma production were significantly increased in B6.me(v+/-) mice after immunization with AChR compared to that of wild type littermates. However, clinical incidence and severity of the disease were not changed. There also were no significant differences in AChR-specific antibodies produced between wild type and me(v+/-) mice. These data suggest that deficiency in SHP-1 expression does decrease the activation threshold of autoreactive T cells in EAMG, but the increased frequency of autoreactive T cells does not aggravate EAMG in terms of clinical score, incidence, or antibody titers.

Molecular and cellular mechanisms of donor cell-induced tolerance

The induction of immunologic tolerance to solid organ allografts is a subject of intense investigation because of the morbidity and mortality associated with standard immunosuppressive therapy. One method that is currently in clinical and preclinical testing involves the transient ablation of recipient T cells using polyclonal antithymocyte sera or monoclonal anti-CD4/CD8 antibody treatment, followed by the posttransplant administration of donor bone marrow cells or of donor peripheral lymphoid populations. Recent studies in our laboratory have shown that the molecular and cellular basis of the prolongation of graft survival by donor cell administration depends on the cellular compartment from which the donor cells were derived. We provide here a brief review of these data followed by new data suggesting that the mode of peripheral and central selection is also dependent on the source from which the donor cells were derived.

Expression of the tyrosine phosphatase SRC homology 2 domain-containing protein tyrosine phosphatase 1 determines T cell activation threshold and severity of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a CD4 Th1-mediated inflammatory demyelinating disorder of the CNS and a well-established animal model for multiple sclerosis. Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) is a cytosolic tyrosine phosphatase that is involved in regulating the T cell activation cascade from signals initiated through the TCR. To study the role of SHP-1 in EAE pathogenesis, we immunized B10.PL mice heterozygous for deletion of the SHP-1 gene (me(v+/-)) and B10.PL wild-type mice with the immunodominant epitope of myelin basic protein (MBP Ac1-11). T cell proliferation and IFN-gamma production were significantly increased in me(v+/-) mice after immunization with MBP Ac1-11. The frequency of MBP Ac1-11-specific CD4 T cells, analyzed by staining with fluorescently labeled tetramers (MBP1-11[4Y]: I-A(u) complexes), was increased in the draining lymph node cells of me(v+/-) mice compared with wild-type mice. In addition, me(v+/-) mice developed a more severe course of EAE with epitope spreading to proteolipid protein peptide 43-64. Finally, expansion of MBP Ac1-11-specific T cells in response to Ag was enhanced in me(v+/-) T cells, particularly at lower Ag concentrations. These data demonstrate that the level of SHP-1 plays an important role in regulating the activation threshold of autoreactive T cells.

Three loci on mouse chromosome 6 influence onset and final incidence of type I diabetes in NOD.C3H congenic strains

The development of insulin-dependent diabetes mellitus in both human and mouse is dependent on the interaction between genetic and environmental factors. The analysis of newly created NOD.C3H congenic strains for spontaneous and cyclophosphamide-induced diabetes has allowed the definition of three controlling genetic loci on mouse chromosome 6. A NOD-derived susceptibility allele at the Idd6 locus strongly influences the onset of diabetes in spontaneous diabetes. A NOD-derived resistance allele at the Idd19 locus affects the final diabetes incidence observed in both models, while a novel locus, provisionally termed Idd20, appears to control Idd19 in an epistatic manner. Decreased diabetes incidence is observed in CY-induced diabetes when Idd20 is homozygous for the C3H allele, while heterozygosity is associated with an increase in diabetes incidence. The Idd20, Idd19, and Idd6 candidate regions fall respectively within genetically defined intervals of 4, 7, and 4.5 cM on mouse chromosome 6. From our YAC contig, Idd6 would appear to localize within a ca. 1.5-Mb region on distal chromosome 6.

Src homology region 2 (SH2) domain-containing phosphatase-1 dephosphorylates B cell linker protein/SH2 domain leukocyte protein of 65 kDa and selectively regulates c-Jun NH2-terminal kinase activation in B cells

Src homology region 2 (SH2) domain-containing phosphatase-1 (SHP-1) is a cytosolic protein tyrosine phosphatase containing two SH2 domains in its NH2 terminus. That immunological abnormalities of the motheaten and viable motheaten mice are caused by mutations in the gene encoding SHP-1 indicates that SHP-1 plays important roles in lymphocyte differentiation, proliferation, and activation. To elucidate molecular mechanisms by which SHP-1 regulates BCR-mediated signal transduction, we determined SHP-1 substrates in B cells using the substrate-trapping approach. When the phosphatase activity-deficient form of SHP-1, in which the catalytic center cysteine (C453) was replaced with serine (SHP-1-C/S), was introduced in WEHI-231 cells, tyrosine phosphorylation of a protein of about 70 kDa was strongly enhanced. Immunoprecipitation and Western blot analyses revealed that this protein is the B cell linker protein (BLNK), also named SH2 domain leukocyte protein of 65 kDa, and that upon tyrosine phosphorylation BLNK binds to SHP-1-C/S in vitro. In vitro kinase assays demonstrated that hyperphosphorylation of BLNK in SHP-1-C/S-expressing cells was not due to enhanced activity of Lyn or Syk. Furthermore, BCR-induced activation of c-Jun NH2-terminal kinase was shown to be significantly enhanced in SHP-1-C/S transfectants. Taken collectively, our results suggest that BLNK is a physiological substrate of SHP-1 in B cells and that SHP-1 selectively regulates c-Jun NH2-terminal kinase activation.

Aberrant expression of the NF-kappaB and IkappaB proteins in B cells from viable motheaten mice

In viable motheaten mice, a mutation in the gene encoding the phosphatase, SHP1, causes severe immunodeficiency and autoimmunity. A defective phosphatase may result in modified phosphorylation of proteins involved in gene regulation. Since the NFkappaB/IkappaB proteins are regulated through phosphorylation, we wished to understand if the expression of these proteins was altered by the SHP1 defect. Splenic B cells from viable motheaten mice were isolated and assessed for purity by flow cytometry. Levels of each protein in isolated B cells were examined by Western blot analyses. Measurement of RNA levels for each protein was assessed by semi-quantitative RT-PCR. Western blots revealed that, in me(v) whole cell lysates, there were reduced levels of RelA and RelB proteins and increased levels of p50 and c-Rel. Furthermore, we analyzed the protein levels of IkappaBalpha and found that, in me(v), this inhibitor was significantly reduced, while the level of another member of the IkappaB family, IkappaBbeta, was not. To determine if these findings in me(v) were secondary to the autoimmune process, we evaluated NF-kappaB/IkappaB expression in the BXSB murine model of autoimmunity. Unlike me(v), B cells from BXSB/Yaa mice had NF-kappaB complexes composed of the RelA submit, and IkappaBalpha was readily detected. In addition, RNA for the RelA and IkappaBalpha proteins in me(v) and control littermates was detected by RT-PCR, indicating that the reduced amounts of these proteins was not exclusively due to transcriptional defects. We conclude that the differences in NF-kappaB/IkappaB proteins that we have described in me(v) are likely a consequences of the SHP1 defect and could contribute to the clinical disorder that characterizes me(v) mice.

Evidence for the presence of insulin-dependent diabetes-associated alleles on the distal part of mouse chromosome 6

Type 1 diabetes (IDDM) is a complex disorder with multifactorial and polygenic etiology. A genome-wide screen performed in a BC1 cohort of a cross between the nonobese diabetic (NOD) mouse with the diabetes-resistant feral strain PWK detected a major locus contributing to diabetes development on the distal part of chromosome 6. Unlike the majority of other Idd loci identified in intraspecific crosses, susceptibility is associated with the presence of the PWK allele. Genetic linkage analysis of congenic lines segregating PWK chromosome 6 segments in a NOD background confirmed the presence of the Idd locus within this region. The genetic interval defined by analysis of congenic animals showed a peak of significant linkage (P = 0.0005) centered on an approximately 9-cM region lying between D6Mit11 and D6Mit25 genetic markers within distal mouse chromosome 6. [Genetic markers polymorphic between the NOD and PWK strains are available as a supplement at http://www.genome.org]

Functional consequences of the SHP-1 defect in motheaten viable mice: role of NF-kappa B

To define the functional consequences of the src-homology domain-1 protein (SHP-1) defect, we examined cytokine production and NF-kappa B activity in motheaten viable (Mev) mice. We found elevated levels of interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor (TNF), and interferon-gamma (IFN-gamma) in Mev mice sera and cultured B and T cells compared to littermate control adult mice. The levels of interleukin-2 (IL-2) detected in Mev sera and activated Mev T cells were decreased, but IL-2 receptor expression was increased. We then evaluated the activity of NF-kappa B and found that this protein is highly expressed in Mev B and T cells. To determine if NF-kappa B had a role in causing the elevated levels of cytokines in Mev mice, we treated activated Mev T cells with an NF-kappa B decoy and found that cell culture treatment with the decoy resulted in significant reduction of the secretion of IL-6, GM-CSF, and TNF, but not IFN-gamma. Therefore, our data show that Mev mice secrete elevated levels of inflammatory cytokines, which can be mediators in the development of the Mev clinical disorder, and that NF-kappa B has an important role in this process, impacting upon the regulation of the immune response.

Mouse models of Hermansky Pudlak syndrome: a review

Hermansky Pudlak Syndrome (HPS) is a recessively inherited disease affecting the contents and/or the secretion of several related subcellular organelles including melanosomes, lysosomes, and platelet dense granules. It presents with disorders of pigmentation, prolonged bleeding, and ceroid deposition, often accompanied by severe fibrotic lung disease and colitis. In the mouse, the disorder is clearly multigenic, caused by at least 14 distinct mutations. Studies on the mouse mutants have defined the granule abnormalities of HPS and have shown that the disease is associated with a surprising variety of phenotypes affecting many tissues. This is an exciting time in HPS research because of the recent molecular identification of the gene causing a major form of human HPS and the expected identifications of several mouse HPS genes. Identifications of mouse HPS genes are expected to increase our understanding of intracellular vesicle trafficking, lead to discovery of new human HPS genes, and suggest diagnostic and therapeutic approaches toward the more severe clinical consequences of the disease.

The natural killer gene complex: a genetic basis for understanding natural killer cell function and innate immunity

The natural killer gene complex encodes proteins, some of which are structurally unrelated, that impact on NK-cell function. Detailed analyses have indicated that these molecules are involved in NK-cell recognition, activation, and inhibition. The importance of this genomic region is highlighted by studies indicating that NKC-associated genes significantly influence NK cell-mediated innate host defense against life-threatening pathogens and that the NKC is conserved among diverse species. Thus, further elucidation of the NKC and its gene products will provide a genetic basis for understanding innate immunity and NK-cell activity at the molecular level.

Transduction of cytotoxic signals in natural killer cells: a general model of fine tuning between activatory and inhibitory pathways in lymphocytes

NK-cells are large granular lymphocytes, which are capable of exerting two major types of effector function, cell cytotoxicity and lymphokine secretion. NK-cells can exert cell cytotoxicity in one of two ways. First, NK-cells are able to recognize and to induce the lysis of antibody-coated target cells during antibody-dependent cell cytotoxicity (ADCC). Second, during natural cytotoxicity NK-cells are also able to recognize and to induce the lysis of a variety of target cells, including primarily virus-infected cells as well as tumor cells. Recently, a novel mechanism has been elucidated which controls NK-cell-activation programs and which is based on the cell surface expression of killer-cell inhibitory receptors (KIR). We will review here the molecular dissection of this inhibitory signalling pathway which utilizes immunoreceptor tyrosine-based inhibition motifs (ITIM) expressed in KIR intracytoplasmic domain. We will also show that this strategy used by NK-cells to regulate their effector functions is a general decision mechanism which exists not only in T- and B-lymphocytes, but also in a variety of other hematopoietic cells.

Hematopoietic cell phosphatase, SHP-1, is constitutively associated with the SH2 domain-containing leukocyte protein, SLP-76, in B cells

Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1; previously named HCP, PTP1C, SH-PTP1, and SHP) is a cytosolic protein tyrosine phosphatase that contains two SH2 domains. Recent data have demonstrated that the gene encoding SHP-1 is mutated in motheaten (mc) and viable motheaten (mc') mice resulting in autoimmune disease. More recently, SHP-1 has been shown to negatively regulate B cell antigen receptor (BCR)-initiated signaling. To elucidate potential mechanisms of SHP-1 action in BCR signal transduction, we studied proteins that interact with SHP-1 in B cells. Both anti-SHP-1 antibody and the two SH2 domains of SHP-1 expressed as glutathione S-transferase fusion proteins precipitated at least three phosphoproteins of approximately 75, 110, and 150 kD upon anti-immunoglobulin M stimulation of the WEHI-231 immature B cell line. Binding of SHP-1 to the 75- and 110-kD proteins appeared to be mediated mainly by the NH2-terminal SH2 domain of SHP-1, whereas both the NH2- and COOH-terminal SH2 domains are required for maximal binding to the 150-kD protein. Immunoprecipitation and Western blot analysis revealed that the SHP-1-associated 75-kD protein is the hematopoietic cell-specific, SH2-containing protein SLP-76. Further, this protein-protein association was constitutively observed and stable during the early phase of BCR signaling. However, significant tyrosine phosphorylation of SLP-76 as well as of SHP-1 was observed after BCR ligation. Constitutive association of SHP-1 with SLP-76 could also be detected in normal splenic B cells. Collectively, these results suggest possible mechanisms by which SHP-1 may modulate signals delivered by BCR engagement.

Production and characterization of fetal sheep pancreatic islet-like cell clusters

Explants of fetal sheep pancreas transplanted into diabetic athymic mice survive for many months but there is only partial differentiation of the endocrine cells. As an alternative form of graft we examined the possibility of creating islet-like cell clusters (ICCs) by collagenase digestion of the fetal sheep pancreas, as has been described for human and porcine fetal pancreas. Such ICCs did form at the rate of 6-23 per 10 mg pancreas; their size varied between 65 and 474 microns (median 232 microns) and their insulin content was 1.6 +/- 0.2 mU per 20 ICCs. Laser scanning confocal analysis showed that 4.6 +/- 0.7% of the cells contained insulin. Insulin was secreted from ICCs maintained in culture at the daily rate of 2.5 mU per 30 ICCs. Arginine but not glucose or theophylline enhanced acute insulin secretion in vitro. Transplantation of up to 1000 ICCs into athymic and acid mice resulted in sparse growth of the epithelial-like cells in the graft and only partial differentiation of the endocrine cells. Hyperglycaemia in diabetic recipients was not normalized. Thus, while functioning ICCs can be created from fetal sheep pancreas, they do not appear to be appropriate for transplantation to reverse diabetes in mice.

Development of fetal sheep pancreas after transplantation into athymic mice

The capacity of the fetal sheep pancreas to grow and function when transplanted into athymic mice was examined to determine whether this source of tissue might be of potential use in reversing diabetes. For this purpose fetal sheep pancreases were obtained in the period between 50 days of gestation and fullterm (148 days). Explants (1 mm3) in organ culture secreted insulin for at least 7 days, but in steadily diminishing amounts. Acute exposure to arginine (10 mM) and theophylline (10 mM), but not glucose (20 mM), calcium chloride (10 mM), and sodium butyrate (10 mM), caused acute secretion of insulin. Explants survived for many months when grafted beneath the renal capsule of athymic mice, but their growth was less, the epithelial-like component smaller, and the percentage of endocrine cells (31 +/- 5%) fewer than the case of transplanted fetal human pancreas. The beta cell was the predominant endocrine cell in the ungrafted fetal sheep pancreas. In the transplanted fetal sheep pancreas this was not so, the alpha and PP cells being dominant--beta:alpha:delta:PP = 3:14:3:11. This pattern was unchanged when the recipient mice were hyperglycaemic--beta:alpha:delta:PP = 4:13:4:28, with no reduction of blood glucose levels being observed for up to 4 mo after transplantation. Altering the site of transplantation to the spleen or liver did not improve survival of the endocrine cells. Fetal sheep pancreatic explants when transplanted into athymic rats failed to survive. Thus, although the unusual pattern of endocrine differentiation in fetal sheep pancreas transplanted into athymic mice makes it an interesting model for further studies of fetal development, it is not of benefit in normalizing the blood glucose levels of the recipients.

Human breast cancer cell line xenografts as models of breast cancer. The immunobiologies of recipient mice and the characteristics of several tumorigenic cell lines

The ability to maintain and study human tissues in an in vivo environment has proved to be a valuable tool in breast cancer research for several decades. The most widely studied tissues have been xenografts of established human breast cancer cell lines into athymic nude mice. Human breast tumor xenografts provide the opportunity to study various important interactions between the tumor and host tissues, including endocrinologic, immunologic, and tumor-stroma interactions. The nude mouse is not the only immune-deficient recipient system in which to study xenografts. Additional single and combined mutant strains have been used successfully, including mice homozygous for the severe combined immune deficiency mutation (scid), both the beige (bg) and nude (nu) mutations in combination (bg/nu), and mice bearing the combined bg/nu/xid mutations. The differing immunobiologies are discussed, with particular reference to the immunobiology of breast cancer, as are the characteristics of several of the more frequently utilized breast cancer xenografts and cell lines. The ability of several endocrine treatments to modulate effectors of cell mediated immunity, e.g., estrogens and antiestrogens, and the effect of site of inoculation on tumor take and metastasis, also are described.

Cytotoxic effects of natural killer cells have no significant role in controlling infection with the intracellular protozoon Eimeria vermiformis

The course of infection with Eimeria vermiformis in C57BL/6J; NK cell-defective C57BL/6J bg/bg; BALB/c; T-cell-defective BALB/c nu/nu; and T-cell-, B-cell-, and NK cell-defective BALB/c x C57BL/6 scid/scid bg/bg mice was monitored. For young C57BL/6J mice, the bg/bg mutants consistently produced fewer oocysts than the controls; there were no differences between older mice of these strains. Wild-type BALB/c mice were more resistant to infection than the nu/nu and scid/scid bg/bg mutants, but there was no difference between the mutants. Treatment of BALB/c mice with poly(I.C) had no effect on the course of infection. These findings confirm the ineffectiveness of NK cells in this system.

Implanted solid human tumours grow under the renal capsule of cyclosporin-immunosuppressed rats

Cyclosporin (CsA) is a potent immunosuppressive drug widely used in organ transplantation. We transplanted fresh surgical samples from human solid malignant tumours into 45 CsA-immunosuppressed rats. Eight out of nine tumour types grew and remained viable for 5 weeks or more in at least two of the transplanted rats. In 29 rats (64%) a distinct growth of primary human tumours was recorded. Five malignancies (intestinal-type gastric carcinoma, adenocarcinoma of the lung, lymph node metastasis of a testicular teratocarcinoma, soft tissue malignant fibrous histiocytoma (MFH), and small-cell sarcoma) showed invasive and progressive growth. In all five cases the largest tumours were 0.9 cm or over in diameter when the rats were killed 5-9 weeks after transplantation. In three cases (adenocarcinoma of the colon, hypernephroma, and a second MFH) the growth of the implants under the kidney capsule was slow, but small living tumour transplants were still found 3-6 weeks later. In every case the microscopic morphology of the xenograft tumour was identical with the original tumour. In two cases the primary xenografts (teratocarcinoma and small-cell sarcoma) were retransplanted into 11 CsA-immunosuppressed rats. In both types the second passage tumours grew, and the take-off and growth rates were comparable to the primary xenografts. Cyclosporin-treated laboratory rats are an alternative to immunodeficient nude and SCID mice for growing fresh human tumour transplants in vivo. Although a few infections were encountered, most of the rats survived the CsA treatment well for up to 2 months.

Molecular basis of the motheaten phenotype

Mice homozygous for the autosomal recessive motheaten (me) or the allelic viable motheaten (mev) mutations manifest a unique immunological disease associated with severe immunodeficiency and autoimmunity. Over the past few years, our group has used the motheaten mouse as a model system for elucidating the genetic and cellular events that contribute to expression of normal hematopoietic and immune cell function. To this end, we have sought to identify the gene responsible for the motheaten phenotype. In our initial studies, our general approach involved the use of subtractive hybridization to identify genes that were differentially expressed in the mutant versus control mice and which might thus provide clues as to the primary gene defect. Using this approach, we showed that genes encoding stefin A cysteine proteinase inhibitors are markedly overexpressed in bone marrow cells of me and mev mice compared to bone marrow cells of normal congenic animals. However, the motheaten mutation has been mapped to mouse choromosome 6 while the stefin A gene cluster was localized to mouse chromosome 16. Stefin gene therefore does not represent the primary gene defect. Our second strategy aimed at identifying the primary gene defect underlying the motheaten phenotype was prompted by the recent localization of a protein tyrosine phosphatase gene to human chromosome 12p12-p13, a region containing a large segment of homology with the region on mouse chromosome 6 where the motheaten locus has been mapped. We have shown that abnormal Hcph transcripts are expressed in me and mev bone marrow cells and that the generation of these altered transcripts is due to RNA splicing defects caused by single basepair changes in the Hcph genes of the mutant mice. These mutant mice thus provide a valuable model system for elucidating the biological roles of HCP in vivo and defining the mechanism whereby defective function of a hematopoietic cell phosphatase leads to expression of the motheaten phenotype of severe immunodeficiency and systemic autoimmunity.

Expression and catalytic activity of the tyrosine phosphatase PTP1C is severely impaired in motheaten and viable motheaten mice

Mutations in the gene encoding the phosphotyrosine phosphatase PTP1C, a cytoplasmic protein containing a COOH-terminal catalytic and two NH2-terminal Src homology 2 (SH2) domains, have been identified in motheaten (me) and viable motheaten (mev) mice and are associated with severe hemopoietic dysregulation. The me mutation is predicted to result in termination of the PTP1C polypeptide within the first SH2 domain, whereas the mev mutation creates an insertion or deletion in the phosphatase domain. No PTP1C RNA or protein could be detected in the hemopoietic tissues of me mice, nor could PTP1C phosphotyrosine phosphatase activity be isolated from cells homozygous for the me mutation. In contrast, mice homozygous for the less severe mev mutation expressed levels of full-length PTP1C protein comparable to those detected in wild type mice and the SH2 domains of mev PTP1C bound normally to phosphotyrosine-containing ligands in vitro. Nevertheless, the mev mutation induced a marked reduction in PTP1C activity. These observations provide strong evidence that the motheaten phenotypic results from loss-of-function mutations in the PTP1C gene and imply a critical role for PTP1C in the regulation of hemopoietic differentiation and immune function.

Role of a genetic region on chromosome 4 in the regulation of natural killer cell activity in mice

Natural killer cell (NK) activity is regulated by both the H-2 and non-H-2 genes. Using bilineal congenic HW26C and HW13 mice which differ from the background strain C57BL/6By (B6) in a region of chromosome 4, we investigated the role played by a gene/genes in a segment of chromosome 4 of BALB/cBy on NK cell activity. Percoll separated low density spleen cells from young HW26C and HW13 mice showed a 3.5 fold higher NK activity than the B6. We also observed that the increase in NK activity of HW26C was not due to an increase in the number of NK cells. Using five other bilineal congenics containing different regions of chromosome 4 of BALB/cBy, we observed that the putative gene(s) regulating NK activity may be located between b and IFN-alpha/beta genes of chromosome 4. The level of NK activity of (B6xHW26C)F1 ranked between the HW26C and B6 suggesting that the gene product described is inherited in an incompletely dominant fashion.

Mutations at the murine motheaten locus are within the hematopoietic cell protein-tyrosine phosphatase (Hcph) gene

Mice homozygous for the recessive allelic mutation motheaten (me) or viable motheaten (mev) on chromosome 6 develop severe defects in hematopoiesis. In this paper we present the findings that the me and mev mutations are within the hematopoietic cell protein-tyrosine phosphatase (Hcph) gene. High resolution mapping localized me to an area tightly linked to Hcph on chromosome 6. Abnormalities of the Hcph protein product were demonstrated by Western blot analysis and by activity assays in both me/me and mev/mev mice. Molecular analysis of the Hcph cDNA identified abnormal transcripts in both mutants. DNA sequence analyses of cDNA and genomic clones revealed that both the me and mev mutations are point mutations that result in aberrant splicing of the Hcph transcript. These findings provide the first available animal models for a specific protein-tyrosine phosphatase deficiency, thus facilitating determination of the precise role of this signaling molecule in hematopoiesis.

Granulated metrial gland cells: a natural killer cell subset of the pregnant murine uterus

The metrial gland develops in the uterus of many rodent species during normal pregnancy. It is a maternally-derived tissue that contains stromal and vascular elements plus a population of large cells, striking in their light microscopic appearance due to the presence of numerous cytoplasmic granules. These cells, which have become known in mice and rats as granulated metrial gland (GMG) cells, are derived from bone marrow precursors and recent work suggests they are a subset of lymphocytes belonging to the natural killer (NK) cell lineage. The functions of GMG cells during normal gestation have not been clearly defined. In vitro, GMG cells have been shown to produce cytokines and their cytokine profile is altered upon addition of medium containing the T cell growth factor interleukin-2 (IL-2). GMG cell granules contain the cytolytic protein perforin but GMG cells have a very limited capacity to kill in vitro unless they have been stimulated by IL-2 or interferon-gamma. Histological study of GMG cells has suggested they preferentially associate with fetal trophoblast. Since trophoblast appears resistant to immune lysis, except by IL-2-activated effector lymphocytes, and because resorbing murine embryos become infiltrated by lytic cells of the NK cell lineage, it is important to establish whether GMG cells are activated by pregnancy-associated events to play a major lytic role in vivo.

Motheaten and viable motheaten mice have mutations in the haematopoietic cell phosphatase gene

Mice with the recessive motheaten (me) or the allelic viable motheaten (mev) mutations express a severe autoimmune and immunodeficiency syndrome. We have shown that the basic defect in these mice involves lesions in the gene which encodes haematopoietic cell phosphatase (HCP). These mice thus provide excellent models for investigating the roles of phosphatases in haematopoiesis and the nature of the genetic and cellular events linking impaired haematopoiesis to severe immunodeficiency and expression of systemic autoimmunity.

The combined immunological and antinociceptive defects of beige-J mice: the possible existence of a 'mu-repressin'

A selective non-responsiveness to the analgesic effects of opioid mu receptor-, but not opioid delta receptor-, mediated antinociception in the tail-flick test has been identified in C57BL/6J-bgJ (beige-J) mice. The beige-J mutation is also known to give rise to multiple immunological disorders and immune cell dysfunctions. A link between these apparently disparate manifestations has been examined in a series of studies using, for example, adoptive transfer of spleen cells. The findings appear to have broad implications for the link between the immune and opioid systems.

The murine pallid mutation is a platelet storage pool disease associated with the protein 4.2 (pallidin) gene

Pallid is one of 12 independent murine mutations with a prolonged bleeding time that are models for human platelet storage pool deficiencies in which several intracellular organelles are abnormal. We have mapped the murine gene for protein 4.2 (Epb4.2) to chromosome 2 where it co-localizes with pallid. Southern blot analyses suggest that pallid is a mutation in the Epb4.2 gene. Northern blot analyses demonstrate a smaller than normal Epb4.2 transcript in affected pallid tissues, such as kidney and skin. This is the first gene defect to be associated with a platelet storage pool deficiency, and may allow the identification of a novel structure or biological pathway that influences granulogenesis.

Comparative studies between nude and scid mice on the growth and metastatic behavior of xenografted human tumors

The growth and metastatic behavior of three human tumor cell lines and a human colon carcinoma previously passaged in vivo were compared between nude mice and scid mice after xenotransplantation. The three human tumor lines included a bladder carcinoma (T24B), a melanoma (RPMI 7931) and a lacZ gene-transduced breast cancer (MDA-MB-435 BAG). The lacZ gene codes for beta-galactosidase, which can be stained blue with chromogenic substrate X-gal, thus allowing the highly sensitive detection and quantitative examination of human cancer metastasis in host mice. Adult (7-14 weeks) NMRI nude and C.B-17 SCID mice were inoculated with 0.5-5 x 10(6) tumor cells s.c. Comparable take rate, latent period and growth rate of implanted tumors were observed in nude and scid mice for each of the cell lines tested. At the time of autopsy, which varied from 6 to 11 weeks after inoculation, a significantly higher incidence of spontaneous lung metastasis was discovered in scid mice (96%) than in age-matched nude mice (27%, total P less than 0.001). In vitro assays for NK cell-mediated cytotoxicity revealed no significant differences between the two strains of mice. Our results suggest that nude and scid mice are equally suitable for propagating human tumors. However, the metastatic capacity of human tumor cells appears to be better expressed in scid mice. Scid mice may therefore provide an advantageous model for the study of human tumor metastasis.

Adoptive transfer of the gld syndrome in double congenic nude lpr mice

Homozygosity for either the lymphoproliferation (lpr) or the generalized lymphoproliferative disease (gld) mutation of mice causes the development of strikingly similar autoimmune and lymphoproliferative syndromes. The relationship between the lpr and gld mutations was studied by grafting B6 gld spleen cells (SC) to athymic B6 nude lpr mice (B6 nulpr) or to B6 nude (B6 nu) mice as controls. The injection of B6 gld SC, but not of B6 wild SC, to B6 nulpr mice caused a prolongation of survival of the short living B6 nulpr recipients. This was associated with elevated anti-single stranded DNA antibody titers and a serum hyperglobulinemia, as well as by a splenomegaly which was nearly as high as in genetically B6 gld mice, and by a marked lymphadenopathy (though milder than that of B6 gld mice). In contrast the [gld----nu] chimaeras showed a more attenuated form of gld-induced syndrome. These results suggest that the lpr environment supplied in athymic lpr recipients is compatible with--and may even favour--the development of the gld-induced syndrome.

Transplantation of normal and leukemic human bone marrow into immune-deficient mice: development of animal models for human hematopoiesis

The successful engraftment of human hematopoietic cells into immune-deficient mice offers a novel approach to characterize the developmental program of human hematopoiesis. While it is not yet possible to achieve high-level engraftment of all human lineages, several methods have been developed to successfully engraft human lymphoid cells and reconstitute partial immune function. In addition to mature cell types, there is evidence that progenitors and perhaps stem cells can engraft the murine bone marrow. Recent work suggests that provision of exogenous human cytokines significantly increases the level of human cell engraftment and stimulates the development of multiple lineages. Progress has also been made to establish animal models of human hematopoietic diseases such as leukemia, autoimmunity, and infectious diseases.

Immunological mutants of the mouse

Mutations at more than 30 loci in mice have been shown to cause deleterious effects on the immune system. Immunologic defects caused by certain of these mutations are determined at the level of hematopoietic progenitor cells or at the level of hematopoietic cell-stromal cell interactions. The immunological mutants described in this paper serve as experimental tools with which to increase our understanding of the development and regulation of the mammalian immune system.

A quick procedure for identifying doubly homozygous immunodeficient scid beige mice

This article describes a rapid and reliable procedure for identifying mice which are doubly homozygous at the scid and beige (bg) loci starting from CB17 scid (no T and B cells) and B6 bg mice (no NK activity). The [scid, bg] mice are directly identified in the F2 progeny by monitoring (1) the hypogammaglobulinemia for the scid gene and (2) the prolonged bleeding associated with the bg gene. Like CB17 scid mice, the [scid, bg] mice show a high susceptibility to infections and die early in life unless they are protected against potential infections. This is achieved by a graft of splenocytes plus bone marrow cells from (B6 bg x CB17 scid) F1 mice. These [scid, bg] mice combine the bg and scid immunodeficiencies and should be better recipients for xenografts than classical scid mice.

Demonstration of a splenic cytotoxic effector cell in mice of genotype SCID/SCID.BG/BG

Splenocytes from mice of genotype scid/scid.bg/bg were tested in vitro to characterize the nature of the immunological deficit in these doubly mutant animals. The cells were unresponsive to the mitogens LPS and Con A and to alloantigens, as predicted for scid/scid genotype. Splenocytes from scid/scid.bg/bg lysed the NK cell-sensitive target cell line YAC at levels approximately 50% lower than those observed for scid/scid splenocytes. Splenocytes from SCID-beige mice failed to lyse the NK-resistant, LAK-sensitive cell line P815 but showed high levels of activity against the murine placental cell line Be6. Lytic activity was found in both nonadherent and plastic adherent cells and was eliminated by pretreatment of the effectors with anti-asialo-GM1 and complement. Incubation of 1 x 10(5) splenocytes with hrIL-2 failed to induce blastogenesis in scid/scid.bg/bg cells but produced a response in cultures of scid/scid or bg/bg spleen cells. However, blastogenesis and elevated levels of LAK-type killing were observed following incubation of higher numbers of scid/scid.bg/bg splenocytes in hrIL-2. Thus, doubly mutant scid/scid.bg/bg mice have reduced NK cell activity, in comparison to scid/scid mice, and appear to possess LAK-like effector cells and LAK cell precursors.

Impaired antibody response of C57BL/6 beige mutant mice to a thymus-independent type 2 antigen

The murine equivalent of the human Chediak-Higashi Syndrome is the beige (bg) mutant in the C57BL/6 (B6) background. Besides the well-known lack of natural killer (NK) activity in bg-homozygous mice, functional abnormalities of T cells, macrophages and various granulocytes have been reported. With the exception of one study indicating a decreased in vitro response to lipopolysaccharide, there is no report concerning the B cell compartment of the beige mutant. The in vivo anti-trinitrophenyl antibody response to a TI-2 antigen (TNP-Ficoll) was found here to be significantly lower in B6 beige than in B6 wild mice, although both strains responded similarly to an analogous TD antigen (TNP-ovalbumin). Since the marginal zone macrophages of the spleen were previously shown to be essential for the initiation of antibody responses to TI-2 antigens, they might be another target of the beige mutation.