Evidence of functional lymphocytes in some (leaky) scid mice

In vivo gene delivery into hCD34+ cells in a humanized mouse model

In vivo targeted gene delivery to hematopoietic stem cells (HSCs) would mean a big step forward in the field of gene therapy. This would imply that the risk of cell differentiation and loss of homing/-engraftment is reduced, as there is no need for purification of the target cell. In vivo gene delivery also bypasses the issue that no precise markers that permit the isolation of a primitive hHSC exist up to now. Indeed, in vivo gene transfer could target all HSCs in their stem-cell niche, including those cells that are "missed" by the purification criteria. Moreover, for the majority of diseases, there is a requirement of a minimal number of gene-corrected cells to be reinfused to allow an efficient long-term engraftment. This requisite might become a limiting factor when treating children with inherited disorders, due to the low number of bone marrow (BM) CD34(+) HSCs that can actually be isolated. These problems could be overcome by using efficient in vivo HSC-specific lentiviral vectors (LVs). Additionally, vectors for in vivo HSC transduction must be specific for the target cell, to avoid vector spreading while enhancing transduction efficiency. Of importance, a major barrier in LV transduction of HSCs is that 75% of HSCs are residing in the G0 phase of the cell cycle and are not very permissive for classical VSV-G-LV transduction. Therefore, we engineered "early-activating-cytokine (SCF or/and TPO)" displaying LVs that allowed a slight and transient stimulation of hCD34(+) cells resulting in efficient lentiviral gene transfer while preserving the "stemness" of the targeted HSCs. The selective transduction of HSCs by these vectors was demonstrated by their capacity to promote selective transduction of CD34(+) cells in in vitro-derived, long-term culture-initiating cell colonies and long-term NOD/SCID repopulating cells. A second generation of these "early-acting-cytokine"-displaying lentiviral vectors has now been developed that is fit for targeted in vivo gene delivery to hCD34(+) cells. In the method presented here, we describe the in vivo gene delivery into hCD34(+) cells by intramarrow injection of these new vectors into humanized BALB/c Rag2( null )/IL2rgc ( null ) (BALB/c RAGA) mice.

Pre-B-cell leukemias in Btk/Slp65-deficient mice arise independently of ongoing V(D)J recombination activity

The adapter protein Slp65 and Bruton's tyrosine kinase (Btk) are key components of the precursor-B (pre-B) cell receptor (pre-BCR) signaling pathway. Slp65-deficient mice spontaneously develop pre-B-cell leukemia, expressing high levels of the pre-BCR on their cell surface. As leukemic Slp65-deficient pre-B cells express the recombination activating genes (Rag)1 and Rag2, and manifest ongoing immunoglobulin (Ig) light-chain rearrangement, it has been hypothesized that deregulated recombinase activity contributes to malignant transformation. In this report, we investigated whether Rag-induced DNA damage is involved in oncogenic transformation of Slp65-deficient B cells. We employed Btk/Slp65 double-deficient mice carrying an autoreactive 3-83μδ BCR transgene. When developing B cells in their bone marrow express this BCR, the V(D)J recombination machinery will be activated, allowing for secondary Ig light-chain gene rearrangements to occur. This phenomenon, called receptor editing, will rescue autoreactive B cells from apoptosis. We observed that 3-83μδ transgenic Btk/Slp65 double-deficient mice developed B-cell leukemias expressing both the 3-83μδ BCR and the pre-BCR components λ5/VpreB. Importantly, such leukemias were found at similar frequencies in mice concomitantly deficient for Rag1 or the non-homologous end-joining factor DNA-PKcs. We therefore conclude that malignant transformation of Btk/Slp65 double-deficient pre-B cells is independent of deregulated V(D)J recombination activity.

Increased expression of cathepsins and obesity-induced proinflammatory cytokines in lacrimal glands of male NOD mouse

PURPOSE

Lacrimal glands (LGs) of male NOD mice, a model of Sjögren's syndrome (SjS), exhibit immune cell infiltration and lipid deposition. The mechanism of SjS was further investigated by characterizing gene expression profiles of NOD mouse LGs in comparison with those of healthy control mice. Differentially expressed genes were further investigated at the protein level to correlate changes in location and abundance with development of disease.

METHODS

Microarray followed by real-time RT-PCR was conducted to compare the gene expression in 12-week-old male NOD mouse LG relative to that in matched BALB/c mouse LG. Immunofluorescence and Western blot analyses were used to localize and quantify proteins of interest. Enzymatic assays measured catalytic activity of cathepsins.

RESULTS

Cathepsin H (Ctsh), S (Ctss), and Z (Ctsz) and proinflammatory factors, including tumor necrosis factor (Tnf), interleukin 6 (Il6), and interleukin 1 beta (Il1b), were upregulated at the mRNA level. Increased cathepsin S immunofluorescence was detected in lysosomes and secretory vesicle-like organelles in LG acinar cells and CD68-positive infiltrating macrophages in NOD mouse LG. Cathepsin S (CATS) and cathepsin H (CATH) activities were significantly higher in NOD mouse LG lysate than in control lysates, and CATS was also significantly elevated in NOD mouse tears.

CONCLUSIONS

Expression of CATS and CATH increases in parallel with proinflammatory cytokines during the development of autoimmune inflammatory disease in the NOD mouse disease model. Tear CATS may represent a biomarker for diagnosis of dacryoadenitis in SjS.

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.

Establishing humanized mice using stem cells: maximizing the potential

Studies on physiology and pathology as they relate to the immune system draw heavily upon rodent models. With the increasing impetus provided by initiatives in translational medicine, the demand for ever more sophisticated, 'humanized' murine models is greater than ever. However, the design and implementation of studies in such mice is far from trivial. Here we provide a technical perspective on the increasing interest in developing humanized mice. We give examples of primary data starting with the routine procurement of human donor material, through CD34(+) cell purification prior to engraftment to injection into immunocompromised mice. Our goal is to provide practical advice to the many investigators who may be commencing or considering such studies.

Fixing DNA breaks during class switch recombination

Immunoglobulin (Ig) class switch recombination (CSR) involves the breakage and subsequent repair of two DNA sequences, known as switch (S) regions, which flank IgH constant region exons. The resolution of CSR-associated breaks is thought to require the nonhomologous end-joining (NHEJ) DNA repair pathway, but the role of the NHEJ factor DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in this process has been unclear. A new study, in which broken IgH-containing chromosomes in switching B cells were visualized directly, clearly demonstrated that DNA-PKcs and, unexpectedly, the nuclease Artemis are involved in the resolution of switch breaks.

Trastuzumab decreases the number of circulating and disseminated tumor cells despite trastuzumab resistance of the primary tumor

We have recently shown that despite of the fact that the ErbB2-positive JIMT-1 human breast cancer cells intrinsically resistant to trastuzumab in vitro, trastuzumab inhibited the outgrowth of early phase JIMT-1 xenografts in SCID mice via antibody-dependent cellular cytotoxicity (ADCC). Here we show that trastuzumab significantly reduces the number of circulating and disseminated tumor cells (CTCs and DTCs) in this xenograft model system at a time when the primary tumor is already unresponsive to trastuzumab. This observation suggests that ErbB2 positive CTCs and DTCs might be sensitive to trastuzumab-mediated ADCC even if when the primary tumor is already non-responsive. Thus, trastuzumab treatment might also be beneficial in the case of patients with breast cancer that is already trastuzumab resistant.

Trastuzumab causes antibody-dependent cellular cytotoxicity-mediated growth inhibition of submacroscopic JIMT-1 breast cancer xenografts despite intrinsic drug resistance

Trastuzumab is a recombinant antibody drug that is widely used for the treatment of breast cancer. Despite encouraging clinical results, some cancers are primarily resistant to trastuzumab, and a majority of those initially responding become resistant during prolonged treatment. The mechanisms of trastuzumab resistance have not been fully understood. We examined the role of antibody-dependent cellular cytotoxicity (ADCC) using JIMT-1 cells that are ErbB2 positive but intrinsically resistant to trastuzumab in vitro. Unexpectedly, in experiments mimicking adjuvant therapy of submacroscopic disease in vivo (JIMT-1 cells inoculated s.c. in severe combined immunodeficiency mice), trastuzumab was able to inhibit the outgrowth of macroscopically detectable xenograft tumors for up to 5-7 weeks. The effect is likely to be mediated via ADCC because trastuzumab-F(ab')(2) was ineffective in this model. Moreover, in vitro ADCC reaction of human leukocytes was equally strong against breast cancer cells intrinsically sensitive (SKBR-3) or resistant (JIMT-1) to trastuzumab or even against a subline of JIMT-1 that was established from xenograft tumors growing despite trastuzumab treatment. These results suggest that ADCC may be the predominant mechanism of trastuzumab action on submacroscopic tumor spread. Thus, measuring the ADCC activity of patient's leukocytes against the tumor cells may be a relevant predictor of clinical trastuzumab responsiveness in vivo.

Transcription factor T-bet regulates skin sclerosis through its function in innate immunity and via IL-13

Tissue remodeling with fibrosis is a predominant pathophysiological mechanism of many human diseases. Systemic sclerosis is a rare, often lethal, disorder of unknown etiology manifested by dermal fibrosis (scleroderma) and excessive connective tissue deposition in internal organs. Currently, there are no available antifibrotic therapeutics, a reflection of our lack of understanding of this process. Animal models of scleroderma are useful tools to dissect the transcription factors and cytokines that govern fibrosis. A disproportionate increase of type 2 cytokines, like TGF-beta and IL-4, more than type 1 cytokines, like IFN-gamma, is thought to underlie the pathogenesis of scleroderma. In this study, we show that mice deficient in the transcription factor T-box expressed in T cells (T-bet), a master regulator of type 1 immunity, display increased sensitivity to bleomycin-induced dermal sclerosis. Despite the well-established role of T-bet in adaptive immunity, we also show that RAG2(-/-) mice, which lack T and B cells, are vulnerable to bleomycin-induced scleroderma and that RAG2/T-bet double-deficient mice maintain the increased sensitivity to bleomycin observed in T-bet(-/-) mice. Furthermore, overexpression of T-bet in T cells does not affect the induction of skin sclerosis in this model. Lastly, we show that IL-13 is the profibrotic cytokine regulated by T-bet in this model. Together, we conclude that T-bet serves as a repressor of dermal sclerosis through an IL-13-dependent pathway in innate immune cells. T-bet, and its transcriptional network, represent an attractive target for the treatment of systemic sclerosis and other fibrosing disorders.

Rat hepatocyte engraftment in severe combined immunodeficient x beige mice using mouse-specific anti-fas antibody

BACKGROUND

Hepatocyte transplantation holds promise as a treatment for acute and chronic liver failure; however, robust model systems needed to study xenogeneic hepatocyte transfer are lacking. Severe combined immunodeficient x beige (SCID/bg) hybrid mice readily accept foreign tissue. Repopulation of C.B-17 SCID/bg mouse liver with rat hepatocytes was studied following induction of mouse hepatocyte apoptosis using an anti-mouse agonistic fas monoclonal antibody (Jo2 mAb) that does not engage xenogeneic fas.

METHODS

SCID/bg mice were transplanted with 1 x 10(6) fresh adult rat hepatocytes intrasplenically and treated with various doses, routes and frequencies of Jo2 mAb. Rat cell repopulation was characterized by quantitative immunofluorescent antibody (q-IFA) staining specific for rat dipeptidyl peptidase type IV (DPP-IV) and leucine amino peptidase, amplification of rat genomic DNA using polymerase chain reaction and histopathological and serum biochemistry analyses.

RESULTS

Analysis of liver sections from mice treated twice weekly for 12 weeks with 0.4 mg/kg Jo2 mAb intraperitoneally consistently demonstrated >50% rat hepatocytes in the parenchymal mass by q-IFA. Rat hepatocyte engraftment protected mice from Jo2 mAb-mediated liver hemorrhage and hepatocyte apoptosis. Serum liver enzyme levels did not increase in Jo2 mAb-treated mice that were highly engrafted with rat hepatocytes, in contrast to matched non-engrafted mice. At 12 weeks post-engraftment, minimal fibrosis and inflammation were apparent and liver architecture had returned to near normal. Jo2 mAb did not induce histopathological abnormalities in other tissues known to express fas antigen (i.e. heart, lung).

CONCLUSIONS

This novel model represents a simple and robust system of xenogeneic hepatocyte transplantation that could be applied to studies of liver biology, regeneration and hepatocyte transplantation.

Tolerosome-induced oral tolerance is MHC dependent

Oral administration of a protein antigen generates a serum factor that induces tolerance when transferred into naïve recipients. This serum factor has been described in rats as consisting of exosome-like structures or tolerosomes, which express major histocompatibility complex class II molecules (MHCII) and mediate antigen-specific tolerance. In this study, we investigated the functions of serum-derived tolerosomes both in vivo and in vitro. Tolerosomes were purified from the 100,000 g pellet fraction of serum from ovalbumin (OVA)-fed mice. When transferred into naïve recipient mice, the tolerosomes mediated OVA-specific tolerance. We also found that tolerosomes from OVA-fed mice induced the activation of OVA-specific T cells both in vivo and in vitro. The inoculation of severe combined immunodeficiency (SCID) mice with an interferon-gamma-producing cell line normalized the expression of MHCII in the intestinal epithelial cells and restored their ability to generate tolerosomes. Syngeneic but not allogeneic transfer of tolerosomes from OVA-fed donors induced tolerance in the recipients. Our results show that tolerosomes can be isolated from mouse serum, that tolerosome-induced oral tolerance requires MHCII expression in intestinal epithelial cells, and that tolerosomes are functional only in syngeneic recipients.

Development of Functional B Cells in a Line of SCID Mice with Transgenes Coding for Anti-Double-Stranded DNA Antibody

Deletion or inactivation of anti-self (DNA) B cells has been reported in non-autoimmune mice bearing Ig transgenes that code for Abs with specificity for dsDNA or ssDNA. However, we report a case in which anti-dsDNA B cells appear to escape both deletion and inactivation. We show that B cells (B220+IgM+) can develop in non-autoimmune SCID mice bearing two site-directed transgenes, 3H9(56R) and Vkappa8, that together code for an anti-dsDNA Ab. The B cells appear inactive, because the mice (56RVkappa8 SCID mice) generally lack serum Ig. However, 56RVkappa8 SCID mice are able to produce IgG Ab with specificity for dsDNA when they become "leaky" for T cells or are reconstituted with exogenous T cells from B cell-deficient JH-/- donors. Thus, anti-dsDNA B cells that escape deletion in 56RVkappa8 SCID mice appear fully functional and can differentiate, class switch, and give rise to IgG-producing cells in the presence of T cells and self-Ag.

Cigarette smoke-induced pulmonary emphysema in scid-mice. Is the acquired immune system required?

BACKGROUND

Chronic obstructive pulmonary disease is associated with a chronic inflammatory response of the host to chronic exposure to inhaled toxic gases and particles. Although inflammatory cells of both the innate and adaptive immune system infiltrate the lungs in pulmonary emphysema and form lymphoid follicles around the small airways, the exact role of the acquired immune system in the pathogenesis of emphysema is not known.

METHODS

In this study, wild type Balb/c mice and immunodeficient scid mice--which lack functional B- and T-cells--were exposed to mainstream cigarette smoke (CS) for 5 weeks or 6 months.

RESULTS

Subacute CS-exposure for 5 weeks significantly increased innate inflammatory cells (neutrophils, macrophages and dendritic cells) in the bronchoalveolar lavage (BAL) fluid of wild type mice and scid mice, which correlated with the CS-induced upregulation of the chemokines Monocyte Chemotactic Protein-1, Macrophage Inflammatory Protein-3alpha and KC (= mouse Interleukin-8). Chronic CS-exposure for 6 months significantly increased the number of neutrophils, macrophages, dendritic cells, CD4+ and CD8+ T-lymphocytes in BAL fluid and lungs of wild type mice compared to air-exposed littermates, and augmented the size and number of peribronchial lymphoid follicles. In contrast, neither B-lymphocytes, nor T-lymphocytes, nor lymphoid follicles could be discerned in the lungs of air- or CS-exposed scid mice. Importantly, chronic CS-exposure induced pulmonary emphysema in both wild type animals and scid mice, as evidenced by a significant increase in the mean linear intercept and the destructive index of CS-exposed versus air-exposed animals. The CS-induced emphysema was associated with increased mRNA expression of matrix metalloproteinase-12 in the lungs and increased protein levels of Tumor Necrosis Factor-alpha in the BAL fluid of CS-exposed Balb/c and scid mice compared to air-exposed littermates.

CONCLUSION

This study suggests that the adaptive immune system is not required per se to develop pulmonary emphysema in response to chronic CS-exposure, since emphysema can be induced in scid mice, which lack lymphoid follicles as well as functional B- and T-cells.

Human lymphoid and myeloid cell development in NOD/LtSz-scid IL2R gamma null mice engrafted with mobilized human hemopoietic stem cells

Ethical considerations constrain the in vivo study of human hemopoietic stem cells (HSC). To overcome this limitation, small animal models of human HSC engraftment have been used. We report the development and characterization of a new genetic stock of IL-2R common gamma-chain deficient NOD/LtSz-scid (NOD-scid IL2Rgamma(null)) mice and document their ability to support human mobilized blood HSC engraftment and multilineage differentiation. NOD-scid IL2Rgamma(null) mice are deficient in mature lymphocytes and NK cells, survive beyond 16 mo of age, and even after sublethal irradiation resist lymphoma development. Engraftment of NOD-scid IL2Rgamma(null) mice with human HSC generate 6-fold higher percentages of human CD45(+) cells in host bone marrow than with similarly treated NOD-scid mice. These human cells include B cells, NK cells, myeloid cells, plasmacytoid dendritic cells, and HSC. Spleens from engrafted NOD-scid IL2Rgamma(null) mice contain human Ig(+) B cells and lower numbers of human CD3(+) T cells. Coadministration of human Fc-IL7 fusion protein results in high percentages of human CD4(+)CD8(+) thymocytes as well human CD4(+)CD8(-) and CD4(-)CD8(+) peripheral blood and splenic T cells. De novo human T cell development in NOD-scid IL2Rgamma(null) mice was validated by 1) high levels of TCR excision circles, 2) complex TCRbeta repertoire diversity, and 3) proliferative responses to PHA and streptococcal superantigen, streptococcal pyrogenic exotoxin. Thus, NOD-scid IL2Rgamma(null) mice engrafted with human mobilized blood stem cells provide a new in vivo long-lived model of robust multilineage human HSC engraftment.

IL-18 Accelerates Atherosclerosis Accompanied by Elevation of IFN-γ and CXCL16 Expression Independently of T Cells

OBJECTIVE

The proatherogenic effect of IL-18 is shown to be dependent on IFN-gamma production. It is believed that activated T cells play a proatherogenic role through secretion of IFN-gamma. However, recent studies in vitro have shown that macrophages, NK cells, and even vascular smooth muscle cells may also secrete IFN-gamma after stimulation by cytokines like IL-18. We therefore investigated whether cells other than activated T cells can play a proatherogenic role via IFN-gamma secretion under the stimulation of IL-18 in vivo.

METHODS AND RESULTS

SCID/apoE knockout mice were injected intraperitoneally with either IL-18 or phosphate-buffered saline 3 times per week for 7 weeks. Our results show that administration of IL-18 leads to 3-fold larger lesions and 2-fold higher circulating IFN-gamma despite the absence of T cells. In addition, increased IFN-gamma, accompanied by elevation of the scavenger receptor/chemokine CXCL16, was observed in both lesions and spleens. Furthermore, our findings revealed that macrophages, NK cells, and vascular cells were the source of IFN-gamma under the stimulation of IL-18 in the absence of T cells in vivo.

CONCLUSIONS

The current data suggest that the proatherogenic effect of IL-18 can occur in the absence of T cells and that IFN-gamma secreted by macrophages, NK cells, and vascular cells is sufficient for the disease progression.

Enhanced engraftment of human cells in RAG2/gammac double-knockout mice after treatment with CL2MDP liposomes

OBJECTIVE

The ability of human cells to repopulate the bone marrow of nonobese diabetic immunodeficient mice (NOD/SCID) is commonly used as a standard assay to quantify the primitive human hematopoietic stem cell population. We studied the applicability of the immunodeficient RAG2(-/-)gammac(-/-) double-knockout mouse for this purpose.

METHODS

RAG2(-/-)gammac(-/-) mice and NOD/SCID mice were injected intravenously (i.v.) with umbilical cord blood-derived CD34(+) cells and engraftment was quantified by determining the human CD45+ cell chimerism in bone marrow at several time points. RAG2(-/-)gammac(-/-) were pretreated with total-body irradiation and depleted of macrophages in liver, spleen, and bone marrow by i.v. injection of clodronate diphosphonate containing liposomes.

RESULTS

We demonstrated that the frequency of chimerism and the level of engraftment in macrophage-depleted RAG2(-/-)gammac(-/-) largely resemble that in NOD/SCID mice. Also similar is the multilineage differentiation pattern in the two mouse strains at 7 weeks after transplantation, with a prominent outgrowth in RAG2(-/-)gammac(-/-) of CD19+ cells (88% +/- 10%). Cells of other lineages were clearly less frequent: 9% +/- 2% myeloid cells and 0.1% +/- 0.1% erythroid cells. As for immature progenitors, 6% +/- 1% of the human cells express the CD34 antigen and 0.4% +/- 0.1% have the CD34+,CD33,38,71(-) phenotype. The presence of human committed progenitors (i.e., CFU-GM/BFU-E) was evident. The persistence of human cells at 4 months after transplantation shows that the RAG2(-/-)gammac(-/-) support long-term maintenance of human hematopoiesis.

CONCLUSION

Our findings indicate that macrophage-depleted RAG2(-/-)gammac(-/-) are a suitable model for studying human hematopoiesis including multipotential stem cells, and long-term repopulation.

A comparison of the in vitro and in vivo activities of IgG and F(ab')2 fragments of a mixture of three monoclonal anti-Her-2 antibodies

PURPOSE

We have demonstrated previously that a mixture of three anti-Her-2 monoclonal antibodies (MAbs) that bind to different epitopes on the extracellular domain of Her-2 expressed on a human breast cancer cell line has more potent antitumor activity than the individual MAbs both in vitro and in xenografted severe combined immunodeficient mice. Because the activity of Herceptin is Fc dependent, we determined whether this would also be the case when a mixture of these three anti-Her-2 MAbs was used.

EXPERIMENTAL DESIGN

IgG and highly purified F(ab')(2) fragments of the anti-Her-2 MAbs and Herceptin were prepared and evaluated for their ability to induce cell death, inhibit vascular endothelial growth factor secretion, and mediate antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity in vitro. They were also compared for their abilities to induce regression of large BT474 tumors in severe combined immunodeficient mice.

RESULTS

All of the F(ab')(2) fragments were >95% pure and, as expected, did not mediate antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity in vitro. The in vitro antiproliferative and proapoptotic effects of the IgGs and F(ab')(2) fragments were similar. In contrast, the IgGs had significant antitumor activity in vivo, whereas their F(ab')(2) fragments were only marginally effective even at 5-fold higher doses to offset their shorter half-lives.

CONCLUSIONS

These results confirm the importance of the Fc portion of Herceptin for optimal in vivo activity and demonstrate that even a mixture of three anti-Her-2 MAbs that are highly effective at inducing cell death in vitro requires Fc-mediated effector function for optimal in vivo activity.

The host resistance locus sst1 controls innate immunity to Listeria monocytogenes infection in immunodeficient mice

Epidemiological, clinical, and experimental approaches have convincingly demonstrated that host resistance to infection with intracellular pathogens is significantly influenced by genetic polymorphisms. Using a mouse model of infection with virulent Mycobacterium tuberculosis (MTB), we have previously identified the sst1 locus as a genetic determinant of host resistance to tuberculosis. In this study we demonstrate that susceptibility to another intracellular pathogen, Listeria monocytogenes, is also influenced by the sst1 locus. The contribution of sst1 to anti-listerial immunity is much greater in immunodeficient scid mice, indicating that this locus controls innate immunity and becomes particularly important when adaptive immunity is significantly depressed. Similar to our previous observations using infection with MTB, the resistant allele of sst1 prevents formation of necrotic infectious lesions in vivo. We have shown that macrophages obtained from sst1-resistant congenic mice possess superior ability to kill L. monocytogenes in vitro. The bactericidal effect of sst1 is dependent on IFN-gamma activation and reactive oxygen radical production by activated macrophages after infection, but is independent of NO production. It is possible that there is a single gene that controls common IFN-dependent macrophage function, which is important in the pathogenesis of infections caused by both MTB and L. monocytogenes. However, host resistance to the two pathogens may be controlled by two different polymorphic genes encoded within the sst1 locus. The polymorphic gene(s) encoded within the sst1 locus that controls macrophage interactions with the two intracellular pathogens remains to be elucidated.

Development and selection of marginal zone B cells

It is now clear that functionally distinct subsets of mature peripheral B cells exist. Of these subsets, marginal zone (MZ) B cells in the spleen are strategically positioned at the blood-lymphoid interface and are programmed to initiate a fast and intense antibody response to blood-borne viral and bacterial agents. Their ability to respond vigorously to antigen and polyclonal activators make MZ B cells key players in the early response to pathogens in the bloodstream. The specialized functions of these innate-like lymphocytes bridge the gap between the early innate immune response and the slower adaptive antibody response, affected mainly by the more prolific follicular B cells. MZ B cells, like B1 cells, are important not only to combat infections but also in the maintenance of host homeostasis. Here we discuss some aspects of MZ B-cell selection and function in health and disease.

Maternal adaptive immunity influences the intestinal microflora of suckling mice

The microflorae in the intestine of breast-fed infants are distinct from those that typically populate the intestine of formula-fed infants. Although the acquisition of passive immunity through breast-feeding may play a critical role in influencing the pattern of bacterial colonization of the gut, the precise mechanisms underlying the differences in the commensal microflorae of breast and formula-fed children have not been established. We hypothesized that the assemblage of commensal microflorae in suckling and weaned mice may be influenced by the maternal adaptive immune system. To test this hypothesis, we analyzed the intestinal microflorae of mice reared in the presence (wild-type) or absence of an intact maternal immune system (T- and B-cell deficient). Several types of bacteria (Lactobacillus, Enterococcus, Clostridium perfringens, Bifidobacterium, and Bacteroides) were isolated and enumerated from both the small and large intestine of 10-, 18-, 25- and 40- to 60-d old mice using selective media. The densities of bacteria were significantly lower in the small intestine of weaned mice that were reared by wild-type (WT) compared with immunodeficient (ID) dams. However, the microflorae were generally more abundant in the large intestine of suckling pups reared by WT compared with ID dams. Our results indicate that intestinal microflorae change throughout the suckling phase of development and that the maternal adaptive immune system influences the pattern and abundance of bacteria within the gut in an age- and site-specific manner.

DNA-dependent protein kinase activity is not required for immunoglobulin class switching

Class switch recombination (CSR), similar to V(D)J recombination, is thought to involve DNA double strand breaks and repair by the nonhomologous end-joining pathway. A key component of this pathway is DNA-dependent protein kinase (DNA-PK), consisting of a catalytic subunit (DNA-PKcs) and a DNA-binding heterodimer (Ku70/80). To test whether DNA-PKcs activity is essential for CSR, we examined whether IgM(+) B cells from scid mice with site-directed H and L chain transgenes were able to undergo CSR. Although B cells from these mice were shown to lack DNA-PKcs activity, they were able to switch from IgM to IgG or IgA with close to the same efficiency as B cells from control transgenic and nontransgenic scid/+ mice, heterozygous for the scid mutation. We conclude that CSR, unlike V(D)J recombination, can readily occur in the absence of DNA-PKcs activity. We suggest nonhomologous end joining may not be the (primary or only) mechanism used to repair DNA breaks during CSR.

Leaky Scid phenotype associated with defective V(D)J coding end processing in Artemis-deficient mice

Radiosensitive severe combined immune deficiency in humans results from mutations in Artemis, a protein which, when coupled with DNA-dependent protein kinase catalytic subunit (DNA-PKcs), possesses DNA hairpin-opening activity in vitro. Here, we report that Artemis-deficient mice have an overall phenotype similar to that of DNA-PKcs-deficient mice-including severe combined immunodeficiency associated with defects in opening and joining V(D)J coding hairpin ends and increased cellular ionizing radiation sensitivity. While these findings strongly support the notion that Artemis functions with DNA-PKcs in a subset of NHEJ functions, differences between Artemis- and DNA-PKcs-deficient phenotypes, most notably decreased fidelity of V(D)J signal sequence joining in DNA-PKcs-deficient but not Artemis-deficient fibroblasts, suggest additional functions for DNA-PKcs. Finally, Artemis deficiency leads to chromosomal instability in fibroblasts, demonstrating that Artemis functions as a genomic caretaker.

IgH class switch recombination to IgG1 in DNA-PKcs-deficient B cells

To assess the role of the DNA-PKcs nonhomologous DNA end-joining (NHEJ) protein in Ig heavy chain class switch recombination (CSR), we assayed CSR ability of DNA-PKcs-deficient (DP-T) B cells generated via complementation of DP-T mice with Ig heavy chain and light chain knock-in transgenes (DP-T/HC/LC mice). DP-T/HC/LC mice were severely deficient for all serum IgH isotypes except IgM and, unexpectedly, IgG1. Upon appropriate stimulation, DP-T/HC/LC B cells showed normal proliferation, germline C(H) gene transcription, and AID induction, indicating that DNA-PKcs deficiency did not affect cellular events upstream to CSR. Yet, in vitro activated DP-T/HC/LC B cells again underwent switching only to IgG1 and, like wild-type cells, frequently underwent CSR to gamma1 on both chromosomes. We conclude that DNA-PKcs is required for CSR to most C(H) genes but that CSR to gamma1 occurs via a DNA-PKcs-independent mechanism.

An orthotopic model of ductal adenocarcinoma of the pancreas in severe combined immunodeficient mice representing all steps of the metastatic cascade

INTRODUCTION

Clinically relevant animal models are needed to evaluate new therapeutic strategies against pancreatic adenocarcinoma, which is almost incurable by established treatment.

AIMS

To establish and characterize a metastatic orthotopic transplant model for pancreatic ductal adenocarcinoma in severe combined immunodeficient (SCID) mice.

METHODOLOGY

Human pancreatic ductal carcinoma cells, PancTu 1, were implanted either subcutaneously or orthotopically into the pancreas.

RESULTS

After 4 weeks, orthotopic transplantation resulted in an extensive local tumor growth of an undifferentiated ductal adenocarcinoma with slight to moderate desmoplastic reaction. The tumor growth and spread resembled the situation in humans, including invasion into adjacent organs causing biliary and stomach obstruction. In addition, tumor metastases to regional lymph nodes of the pancreas, lung, liver, mesentery, and diaphragm, and attached to the kidneys, spleen, and reproductive organs were observed. In contrast, no invasion or metastases could be demonstrated by subcutaneous implanted PancTu I cells. Using immunohistochemical analysis, even single human tumor cells could be detected in blood vessels and metastatic organs, providing evidence that the orthotopic transplant model appropriately reflects the entire process of the metastatic cascade.

CONCLUSION

This cancer model in SCID mice appears to be a powerful tool to investigate the identity of metastasis-associated genes and to evaluate preclinically the potency of novel antimetastatic agents in ductal adenocarcinoma of the pancreas.

GM-CSF and IL-2 induce specific cellular immunity and provide protection against Epstein-Barr virus lymphoproliferative disorder

Epstein-Barr virus-associated lymphoproliferative disease (EBV-LPD) is a potentially life-threatening complication in immune-deficient patients. We have used the severe combined immune deficient (SCID) mouse engrafted with human leukocytes (hu-PBL-SCID) to evaluate the use of human cytokines in the prevention of EBV-LPD in vivo. Daily low-dose IL-2 therapy can prevent EBV-LPD in the hu-PBL-SCID mouse, but protection is lost if murine natural killer (NK) cells are depleted. Here we demonstrate that combined therapy with human GM-CSF and low-dose IL-2 is capable of preventing EBV-LPD in the hu-PBL-SCID mouse in the absence of murine NK cells. Lymphocyte depletion experiments showed that human NK cells, CD8(+) T cells, and monocytes were each required for the protective effects of GM-CSF and IL-2 combination therapy. This treatment resulted in a marked expansion of human CD3(+)CD8(+) lymphocytes in vivo. Using HLA tetramers complexed with EBV immunodominant peptides, a subset of these lymphocytes was found to be EBV-specific. These data establish that combined GM-CSF and low-dose IL-2 therapy can prevent the immune deficiencies that lead to fatal EBV-LPD in the hu-PBL-SCID mouse depleted of murine NK cells, and they point to a critical role for several human cellular subsets in mediating this protective effect.

Inhibitory effect of a matrix metalloproteinase inhibitor on growth and spread of human pancreatic ductal adenocarcinoma evaluated in an orthotopic severe combined immunodeficient (SCID) mouse model

The present study was aimed at evaluating the effect of the matrix metalloproteinase (MMP) inhibitor prinomastat (AG3340) on tumor progression using an orthotopic pancreatic carcinoma model in severe combined immunodeficient mice. In controls, receiving vehicle only, the poorly differentiated ductal adenocarcinoma invaded into adjacent organs and metastasized to different sites in the abdomen and to the lungs. Treatment with prinomastat, intraperitoneally twice daily for 21 days, reduced primary tumor volume significantly to 19.0 (+/-7.7)% of control, with induction of necrosis, differentiation, and fibrotic tissue in the pancreatic tumors. Invasion was not observed in 63% of prinomastat-treated mice, and metastases were reduced markedly. Surprisingly, prinomastat-treated tumors had on average higher microvessel densities as a consequence of an increased angiogenesis in perinecrotic tumor areas. We conclude that prinomastat is highly effective in inhibiting pancreatic carcinoma growth and progression in an orthotopic cancer model. This model appears to be a valuable tool to investigate the potency of novel antimetastatic strategies in pancreatic ductal adenocarcinoma by specifically targeting certain MMPs.

Lack of B cell leakiness in BALB/cA-nu, scid double mutant mice

BALB/cA mice homozygous for both nu and scid mutations (BALB/cA-nu/nu, scid/scid) were developed by mating between BALB/cA-scid and BALB/cA-nu. These mice have greater longevity than C.B-17-scid because no thymic lymphoma occurs in them unlike in the latter. C.B-17-scid is known to show the leaky phenomenon in which a few clones of functional T and B cells develop in aged C.B-17-scid. Unexpectedly, the leaky B cells and T cells were absent or suppressed in BALB/cA-nu, scid mice when cytokine expressions were determined by RT-PCR, lymphocyte phenotypes by flow cytometry and serum immunoglobulin levels by ELISA. These results indicate that B cell leakiness may be induced by leaked T cells. BALB/cA-nu, scid mice may be useful as a recipient in allo- and xeno-transplantation experiments because of the absence of both thymic lymphomas and leakiness, in addition to lack of hair.

Islet xenograft destruction in the hu-PBL-severe combined immunodeficient (SCID) mouse necessitates anti-CD3 preactivation of human immune cells

Introduction of the hu-PBL-SCID mouse model has yielded a potentially useful tool for research in transplantation. The aim of this study was to define the conditions necessary for a reconstituted human immune system to destroy in a consistent manner rat islet xenografts in the alloxan-diabetic hu-PBL-SCID mouse. We examined different time points of hu-PBL reconstitution, different transplantation sites of the islets and several hu-PBL reconstitution protocols. Major differences in graft destruction were observed between the different hu-PBL reconstitution protocols, irrespective of timing of hu-PBL reconstitution or site of transplantation. Although preactivation of hu-PBL did not improve the level of hu-PBL chimerism, histological and immunohistochemical analysis of the grafts revealed a severe human lymphocytic infiltration and beta cell destruction only in the grafts of mice receiving preactivated hu-PBL. This beta cell injury resulted in impaired glucose tolerance, with in some animals recurrence of hyperglycaemia, and decreased insulin and C-peptide levels after glucose stimulation. Therefore, we conclude that activation of hu-PBL prior to transfer is essential in achieving xenograft infiltration and destruction in hu-PBL-SCID mice. The need for immune manipulation suggests that interactions between hu-PBL and xenografts in this model may be hampered by incompatibilities in cross-species adhesion and/or activation signals.

The growth and metastasis of human, HER-2/neu-overexpressing tumor cell lines in male SCID mice

HER-2/neu is overexpressed on a variety of human adenocarcinomas and overexpression has been associated with a poor prognosis. For this reason, HER-2 has become an attractive target for immunotherapy. To facilitate testing of anti-HER-2-monoclonal antibodies (MAbs) and immunotoxins (ITs), we have evaluated the in vivo growth and metastatic spread of three HER-2-overexpressing human breast cancer cell lines (BT474, MDA-MB-453 and HCC1954) and one ovarian cancer cell line (SKOV3.ip1) in pre-irradiated male SCID mice using subcutaneous (s.c.), intravenous (i.v.) and intraperitoneal (i.p.) routes of injection. All the cell lines tested grew as s.c. tumors and the growth of BT474 and MDA-MB-453 cells after s.c. injection was improved by co-inoculation with Matrigel. Metastases to the lungs were detectable by PCR or histopathology after s.c. injection of BT474 and to a much lesser extent after s.c. injection of HCC1954, MD-MB-453 and SKOV3.ip1 cells. I.p. injection of HCC1954 and SKOV3.ip1 cells produced fatal ascites while i.v. injection of SKOV3.ip1, but not BT474 or MDA-MB-453 cells, resulted in infiltration of lungs and death within 9-11 weeks.

Defective embryonic neurogenesis in Ku-deficient but not DNA-dependent protein kinase catalytic subunit-deficient mice

Mammalian nonhomologous DNA end joining employs Ku70, Ku80, DNA-dependent protein kinase catalytic subunit (DNA-PKcs), XRCC4, and DNA ligase IV (Lig4). Herein, we show that Ku70 and Ku80 deficiency but not DNA-PKcs deficiency results in dramatically increased death of developing embryonic neurons in mice. The Ku-deficient phenotype is qualitatively similar to, but less severe than, that associated with XRCC4 and Lig4 deficiency. The lack of a neuronal death phenotype in DNA-PKcs-deficient embryos and the milder phenotype of Ku-deficient versus XRCC4- or Lig4-deficient embryos correlate with relative leakiness of residual end joining in these mutant backgrounds as assayed by a V(D)J recombination end joining assay. We conclude that normal development of the nervous system depends on the four evolutionarily conserved nonhomologous DNA end joining factors.

NOD/LtSz-Rag1null mice: an immunodeficient and radioresistant model for engraftment of human hematolymphoid cells, HIV infection, and adoptive transfer of NOD mouse diabetogenic T cells

Development of a small animal model for the in vivo study of human immunity and infectious disease remains an important goal, particularly for investigations of HIV vaccine development. NOD/Lt mice homozygous for the severe combined immunodeficiency (Prkdcscid) mutation readily support engraftment with high levels of human hematolymphoid cells. However, NOD/LtSz-scid mice are highly radiosensitive, have short life spans, and a small number develop functional lymphocytes with age. To overcome these limitations, we have backcrossed the null allele of the recombination-activating gene (Rag1) for 10 generations onto the NOD/LtSz strain background. Mice deficient in RAG1 activity are unable to initiate V(D)J recombination in Ig and TCR genes and lack functional T and B lymphocytes. NOD/LtSz-Rag1null mice have an increased mean life span compared with NOD/LtSz-scid mice due to a later onset of lymphoma development, are radioresistant, and lack serum Ig throughout life. NOD/LtSz-Rag1null mice were devoid of mature T or B cells. Cytotoxic assays demonstrated low NK cell activity. NOD/LtSz-Rag1null mice supported high levels of engraftment with human lymphoid cells and human hemopoietic stem cells. The engrafted human T cells were readily infected with HIV. Finally, NOD/LtSz-Rag1null recipients of adoptively transferred spleen cells from diabetic NOD/Lt+/+ mice rapidly developed diabetes. These data demonstrate the advantages of NOD/LtSz-Rag1null mice as a radiation and lymphoma-resistant model for long-term analyses of engrafted human hematolymphoid cells or diabetogenic NOD lymphoid cells.

A mathematical model predicting the frequency of aberrant rearrangements in the T-cell receptor gene

The T-cell receptor (TCR) genetic loci undergo an orderly process of recombination in ontogeny in order to generate a diverse array of antigen receptors. Normally occurring, out-of-frame and incomplete rearrangements produce non-productive TCR transcripts. Abnormalities in the rearrangement process occur at very low frequencies but may predominate in inborn errors of recombination. Detecting these abnormalities in surviving pools of lymphocytes is difficult and typically focuses on identification of abnormally rearranged alleles or on detecting abnormalities in recombinase proteins. Thus, there currently exists no rapid screening method to identify aberrant V(D)J recombination. To address this issue, a mathematical model was developed to predict the error rate from the measured proportions of different non-productive TCR alleles. Since the proportions of different non-productive rearrangements vary in a characteristic fashion in response to abnormalities in the recombination process, the mathematical model presented here provides a tool to indirectly assess the error rate of TCR recombination. The model was applied to a group of patients with Omenn's syndrome, most of whom had an unknown primary defect. The results indicate that these patients had a > 90% rate of aberrant TCR recombination.

In vivo models for Epstein-Barr virus (EBV)-associated B cell lymphoproliferative disease (BLPD)

EBV infects B lymphocytes in vivo and establishes a life-long persistent infection in the host. The latent infection is controlled by EBV-specific MHC class 1-restricted CTL. Immunosuppression reduces CTL activity, and this facilitates outgrowth of EBV+ve B cell lymphoproliferative disease (BLPD). BLPD are aggressive lesions with high mortality. This review presents some key facets in the development of EBV-associated BLPD and in vivo studies on its pathogenesis. The animal models used to date include the common marmoset (Callithrix jacchus), the cottontop tamarin (Saguinus oedipus oedipus), rhesus monkey, murine herpesvirus 68 (MHV68), and the severe combined immunodeficient (scid) mouse, each of which has been used to address particular aspects of EBV biology and BLPD development. Scid mice inoculated i.p. with PBMC from EBV-seropositive individuals develop EBV+ve BLPD-like tumours. Thus this small animal model (hu-PBMC-scid) is currently used by many laboratories to investigate EBV-associated diseases. We and others have studied BLPD pathogenesis in the hu-PBMC-scid model and shown that EBV+ve B cells on their own do not give rise to tumours in this model without inclusion of autologous T cell subsets in the inoculum. Based on the findings that (1) established tumours do not contain T cells and (2) tumour cells express a variety of B cell growth factors, a stepwise model of lymphomagenesis in the scid mouse model can be defined. Additionally, the hu-PBMC-scid model can be used to assess novel therapeutic regimes against BLPD before introduction into a clinical setting.

Anti-inflammatory effects of systemic anti-tumour necrosis factor alpha treatment in human/murine SCID arthritis

OBJECTIVES

To evaluate in vivo the contribution of tumour necrosis factor alpha (TNFalpha) to the chimeric transfer model of human rheumatoid arthritis synovial membrane into SCID mice (hu/mu SCID arthritis), systemic anti-TNFalpha treatment was performed and the clinical, serological, and histopathological effects of this treatment assessed.

METHODS

Animals were treated with the rat-antimouse TNFalpha monoclonal antibody V1q, starting on day 1 after hu/mu engraftment, twice weekly for 12 weeks. Joint swelling, serum concentrations of human and murine interleukin 6 (IL6), and serum amyloid P (SAP) were measured. Histopathological and immunohistochemical analyses of the joints were also performed at the end of treatment.

RESULTS

Neutralisation of murine TNFalpha induced the following effects: (a) reduction of extent and duration of the acute arthritis phase, with significant reduction of joint swelling at two weeks; (b) decrease of murine SAP concentrations after the first antibody administration; and (c) increase of murine IL6 in the serum. At the end of treatment, there was a significant reduction of the inflammatory infiltration in the engrafted joints. Because of the mild degree of joint erosion, no treatment effects could be demonstrated on the destructive process.

CONCLUSION

In the lymphocyte independent hu/mu SCID arthritis, anti-TNFalpha treatment reduces local and systemic signs of inflammation.

A novel immunodeficient mouse model--RAG2 x common cytokine receptor gamma chain double mutants--requiring exogenous cytokine administration for human hematopoietic stem cell engraftment

Gene transduction into immature human hematopoietic cells collected from umbilical cord blood, bone marrow, or mobilized peripheral blood cells could be useful for the treatment of genetic and acquired disorders of the hematopoietic system. Immunodeficient mouse models have been used frequently as recipients to assay the growth and differentiation of human hematopoietic stem/progenitor cells. Indeed, high levels of human cell engraftment were first reported in human/murine chimeras using NOD/SCID mice, which now are considered as the standard for these types of experiments. However, NOD/SCID mice have some clear disadvantages (including spontaneous tumor formation) that limit their general use. We have developed a new immunodeficient mouse model by combining recombinase activating gene-2 (RAG2) and common cytokine receptor gamma chain (gamma c) mutations. The RAG2-/-/gamma c- double mutant mice are completely alymphoid (T-, B-, NK-), show no spontaneous tumor formation, and exhibit normal hematopoietic parameters. Interestingly, human cord blood cell engraftment in RAG2-/-/gamma c- mice was greatly enhanced by the exogenous administration of human cytokines interleukin-(IL-3) granulocyte-macrophage colony-stimulating factor, (GM-CSF), and erythropoietin in contrast to the NOD/SCID model. This unique feature of the RAG2-/-/gamma c- mouse model should be particularly well suited for assessing the role of different cytokines in human lymphopoiesis and stem/progenitor cell function in vivo.

Suppression of Antigen-Specific Th2 Cell-Dependent IgM and IgG1 Production Following Norepinephrine Depletion In Vivo

The mechanism by which the Th2 cell-dependent Ab response is modulated by the sympathetic neurotransmitter norepinephrine (NE) was investigated. Our model system used the severe combined immunodeficient (scid) mouse that was depleted of NE with 6-hydroxydopamine before reconstitution with a clone of β2-adrenergic receptor (β2AR)neg KLH-specific Th2 cells and resting trinitrophenyl (TNP)-specific β2ARpos B cells enriched from the spleens of unimmunized mice. Following challenge with TNP-keyhole limpet hemocyanin (KLH), Ab production in these mice was hapten-, carrier-, and allotype-specific as well as MHC restricted. Depletion of NE resulted in a 50–75% suppression of the primary anti-TNP IgM response compared with that of NE-intact controls, while the secondary IgM response returned to control levels. In contrast, both the primary and secondary anti-TNP IgG1 responses were suppressed by 85 and 40%, respectively. Using NE-intact mice exposed to either a βAR- or αAR-selective antagonist, the effect of NE on the Ab response was shown to be mediated by the βAR. In addition, administration of a β2AR-selective agonist to NE-depleted mice partially reversed the suppressed Ab response that resulted from NE depletion. Expression of the β2AR on TNP-specific B cells was confirmed by radioligand binding, immunofluorescence, and cAMP analysis. Also, while splenic histology was comparable in NE-intact and NE-depleted mice before Ag exposure, follicle expansion and germinal center formation were suppressed in NE-depleted mice after Ag exposure. Taken together, these results suggest that NE stimulation of the β2AR expressed on B cells is necessary for the maintenance of an optimal primary and secondary Th2 cell-dependent Ab response in vivo.

Human immune response to a peptide mimic of Neisseria meningitidis serogroup C in hu-PBMC-SCID mice

An anti-idiotype-based peptide mimic vaccine for Neisseria meningitidis serogroup C polysaccharide (MCPS) has been developed and shown to induce a response in mice that is specific, functional, and T-dependent. In this study, the immunogenicity of the MCPS peptide mimic vaccine preparation, as a potential vaccine for use in humans, is shown using the hu-PBMC-SCID mouse model. The human antibody response to the MCPS peptide mimic vaccine is specific and functional as shown by inhibition enzyme-linked immunoadsorbent assay (ELISA) and bactericidal assay. These data support the usefulness of the peptide mimic vaccine strategy for humans.

Severe leukopenia and dysregulated erythropoiesis in SCID mice persistently infected with the parvovirus minute virus of mice

Parvovirus minute virus of mice strain i (MVMi) infects committed granulocyte-macrophage CFU and erythroid burst-forming unit (CFU-GM and BFU-E, respectively) and pluripotent (CFU-S) mouse hematopoietic progenitors in vitro. To study the effects of MVMi infection on mouse hemopoiesis in the absence of a specific immune response, adult SCID mice were inoculated by the natural intranasal route of infection and monitored for hematopoietic and viral multiplication parameters. Infected animals developed a very severe viral-dose-dependent leukopenia by 30 days postinfection (d.p.i.) that led to death within 100 days, even though the number of circulating platelets and erythrocytes remained unaltered throughout the disease. In the bone marrow of every lethally inoculated mouse, a deep suppression of CFU-GM and BFU-E clonogenic progenitors occurring during the 20- to 35-d.p.i. interval corresponded with the maximal MVMi production, as determined by the accumulation of virus DNA replicative intermediates and the yield of infectious virus. Viral productive infection was limited to a small subset of primitive cells expressing the major replicative viral antigen (NS-1 protein), the numbers of which declined with the disease. However, the infection induced a sharp and lasting unbalance of the marrow hemopoiesis, denoted by a marked depletion of granulomacrophagic cells (GR-1(+) and MAC-1(+)) concomitant with a twofold absolute increase in erythroid cells (TER-119(+)). A stimulated definitive erythropoiesis in the infected mice was further evidenced by a 12-fold increase per femur of recognizable proerythroblasts, a quantitative apoptosis confined to uninfected TER-119(+) cells, as well as by a 4-fold elevation in the number of circulating reticulocytes. Therefore, MVMi targets and suppresses primitive hemopoietic progenitors leading to a very severe leukopenia, but compensatory mechanisms are mounted specifically by the erythroid lineage that maintain an effective erythropoiesis. The results show that infection of SCID mice with the parvovirus MVMi causes a novel dysregulation of murine hemopoiesis in vivo.

T-Cell Receptor Analysis in Omenn’s Syndrome: Evidence for Defects in Gene Rearrangement and Assembly

Patients with Omenn’s syndrome have a form of severe immune deficiency that is associated with pathological features of graft-versus-host disease, except for the lack of foreign engraftment. It has been hypothesized that the disease’s unique clinical features are mediated by an expanded population of autologous self-reactive T cells of limited clonality. In the current study, an investigation of the T-cell receptor (TCR) repertoire was undertaken to identify defects in T-cell rearrangement and development. The TCR repertoire in this group of patients was exquisitely restricted in the number of different TCR clonotypes, and some of these clonotypes seemed to have similar recognition motifs in the antigen-binding region, indicating antigen-driven proliferation of T lymphocytes. The TCRs from some patients lacked N- or P-nucleotide insertions and used proximal variable and joining gene segments, suggesting abnormal intrathymic T-cell development. Finally, abnormal assembly of gene segments and truncated rearrangements within nonproductive alleles suggested abnormalities in TCR rearrangement mechanisms. Overall, the findings suggest that inefficient and/or abnormal generation of TCRs may be a consistent feature of this disease.

T-Cell Receptor Analysis in Omenn’s Syndrome: Evidence for Defects in Gene Rearrangement and Assembly

Patients with Omenn’s syndrome have a form of severe immune deficiency that is associated with pathological features of graft-versus-host disease, except for the lack of foreign engraftment. It has been hypothesized that the disease’s unique clinical features are mediated by an expanded population of autologous self-reactive T cells of limited clonality. In the current study, an investigation of the T-cell receptor (TCR) repertoire was undertaken to identify defects in T-cell rearrangement and development. The TCR repertoire in this group of patients was exquisitely restricted in the number of different TCR clonotypes, and some of these clonotypes seemed to have similar recognition motifs in the antigen-binding region, indicating antigen-driven proliferation of T lymphocytes. The TCRs from some patients lacked N- or P-nucleotide insertions and used proximal variable and joining gene segments, suggesting abnormal intrathymic T-cell development. Finally, abnormal assembly of gene segments and truncated rearrangements within nonproductive alleles suggested abnormalities in TCR rearrangement mechanisms. Overall, the findings suggest that inefficient and/or abnormal generation of TCRs may be a consistent feature of this disease.

T lymphocytes are not the target for estradiol-mediated suppression of DTH in reconstituted female severe combined immunodeficient (SCID) mice

Oestrogen has the capacity to suppress T cell-dependent DTH. To explore the mechanisms whereby oestrogen exerts its effects on the immune system we have used SCID mice which are largely devoid of functional T and B lymphocytes, hence being unable to raise DTH, but display intact antigen-presenting capacity. Transfer of lymphocytes to SCID mice restores the DTH capacity. In order to analyse if oestrogen down-regulates DTH by a direct action on T cells we reconstituted SCID mice with either splenocytes or thymocytes from congenic C.B-17 or allogeneic B6 donor mice. Either donor or recipient mice were exposed to estradiol before cell transfer. DTH response was registered in recipient SCID mice 1 and 3 weeks after challenge with oxazolone (OXA). SCID mice receiving estradiol-exposed spleen cells from congenic or allogeneic donor mice displayed lower DTH responses compared with control mice. In contrast, SCID mice receiving estradiol-exposed thymocytes from congenic donor mice showed no significant difference in DTH response compared with control mice. Estradiol-treated SCID mice, transferred with either spleen cells or thymocytes from congenic, hormonally non-treated donors, displayed a significantly lower DTH response compared with control mice. In contrast, estradiol-treated SCID mice receiving hormonally non-treated allogeneic spleen cells showed no difference in DTH response compared with control mice. The results show that T lymphocytes are not the target cell population for estradiol-mediated suppression of DTH in reconstituted female SCID mice.

Enhanced human cell engraftment in mice deficient in RAG2 and the common cytokine receptor gamma chain

Xenotransplantation of human cells into immunodeficient mice has been used to develop models of human haemopoiesis and lymphoid cell function. However, the utility of existing mouse strains can be limited by shortened life-spans, spontaneous production of functional lymphocytes with ageing, and residual innate immunity leading to variable levels of engraftment. Mice with a deletion of the common cytokine receptor gamma chain (gamma c) gene have reduced numbers of peripheral T and B lymphocytes, and absent natural killer cell (NK) activity. A genetic cross with a recombinase activating gene 2 (RAG2)-deficient strain produced mice doubly homozygous for the gamma c and RAG2 null alleles (gamma c-/RAG2-). These mice have a stable phenotype characterized by the absence of all T lymphocyte. B lymphocyte and NK cell function. Injection of human B-lymphoblastoid cells resulted in earlier fatal metastatic lymphoproliferative disease than in NOD/LtSz-scid controls. This was particularly evident in animals injected intravenously, possibly because of residual NK activity in NOD/LtSz-scid mice. Levels of engraftment with peripheral-blood-derived human lymphocytes were also increased and associated with higher CD4/CD8 ratios. These findings demonstrate that this new strain of immunodeficient mice has significant advantages over existing strains for engraftment of human cells, and may be useful for study of adoptive immunotherapy and novel therapies for GvHD and HIV infection.

The use of an anti-CD3 immunotoxin to prevent the development of lymphoproliferative disease in SCID/PBL mice

Severe combined immunodeficient mice (SCID) reconstituted with normal PBLs (SCID/PBL) from Epstein-Barr virus-positive (EBV+) human donors often develop fatal human B lymphomas which resemble the EBV-induced lymphoproliferative disease (LPD) observed in immunosuppressed individuals. This phenomenon appears to be T cell dependent. In this study we used an immunotoxin (IT) prepared by conjugating the monoclonal anti-CD3 antibody, 64.1, to deglycosylated ricin A chain (dgRTA) to prevent LPD in SCID/PBL mice. We show that the incidence of LPD is greatly reduced by either a combination of in vitro treatment of PBLs followed by one in vivo treatment of the xenografted mice with 64.1-dgRTA immunotoxin or by repeated treatments in vivo with the immunotoxin. In contrast, in vitro treatment alone or in vivo treatment with only one injection of 64.1-dgRTA were less effective. As expected, this IT did not have any non-specific cytotoxic effects on already established EBV+ tumors from SCID/PBL mice. The use of this IT, therefore, represents a simple method to avoid LPD when injecting blood-containing tissues into SCID mice.

A targeted DNA-PKcs-null mutation reveals DNA-PK-independent functions for KU in V(D)J recombination

The DNA-dependent protein kinase (DNA-PK) consists of Ku70, Ku80, and a large catalytic subunit, DNA-PKcs. Targeted inactivation of the Ku70 or Ku80 genes results in elevated ionizing radiation (IR) sensitivity and inability to perform both V(D)J coding-end and signal (RS)-end joining in cells, with severe growth retardation plus immunodeficiency in mice. In contrast, we now demonstrate that DNA-PKcs-null mice generated by gene-targeted mutation, while also severely immunodeficient, exhibit no growth retardation. Furthermore, DNA-PKcs-null cells are blocked for V(D)J coding-end joining, but retain normal RS-end joining. Finally, while DNA-PK-null fibroblasts exhibited increased IR sensitivity, DNA-PKcs-deficient ES cells did not. We conclude that Ku70 and Ku80 may have functions in V(D)J recombination and DNA repair that are independent of DNA-PKcs.

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.

CD4-CD8-C.B-17 SCID thymocytes enter the CD4+CD8+ stage in the presence of neonatally grafted T cells

The aim of this work was to study the selection of donor T cells and their influence on thymic development in C.B-17 scid/scid (severe combined immunodeficient; SCID) mice during chronic graft-versus-host disease (GVHD). Recipient SCID mice (H-2d), neonatally grafted with allogeneic peripheral T cells from CBA/J strain (H-2k) of mice, only developed a mild acute GVHD, and were, at the chronic stage, devoid of pathological symptoms. Thymic cell numbers of injected mice differed from 10(5) to 1.2 x 10(7) at 2-3 weeks post-injection (p.i.), and from 4 x 10(5) to 8.5 x 10(7) at 2 months p.i. In these mice, the thymus size was correlated to the CD4-CD8- (double negative; DN) to CD4+CD8+ (double positive; DP) cell ratio, where at 2 months p.i., 8 out of 16 treated SCID mice contained 5 x 10(6) cells or more and also possessed the highest frequencies of endogenous DP cells (25-95%). In contrast to previous findings, peripheral donor T cells from allogeneic and syngeneic mice, infiltrating the host thymus, had a positive effect on the development of endogenous DP thymocytes. Furthermore, these thymocytes were developmentally blocked at the DP stage, occasionally in combination with the expression of CD25, CD44 and CD117 but in the absence of T-cell receptor (TCR) expression. Also, at this time-point, the CBA/J donor TCR Vbeta repertoire was equal to that of normal CBA/J mice, but purified responding donor cells were proliferatively inhibited against H-2d stimulators in ex vivo mixed lymphocyte cultures. In contrast, the same responders showed a pronounced proliferation against syngeneic H-2Kk stimulators, suggesting either a reversion from anergy of autoreactive CBA/J T cells or a vast expansion of multiple self-reactive T-cell clones, when parked in a milieu with a lower concentration of self-antigens.

Dendritic Cells and Macrophages Are the First and Major Producers of TNF-α in Pancreatic Islets in the Nonobese Diabetic Mouse

The nonobese diabetic (NOD) mouse spontaneously develops autoimmune insulin-dependent diabetes mellitus (IDDM) and serves as an animal model for human type I diabetes. TNF-α is known to be produced by islet-infiltrating mononuclear cells during insulitis and subsequent β cell destruction and has been implicated in the pathogenesis of IDDM. Previously, T cells have been suggested as the main source of TNF-α in the islet infiltrate. However, on immunohistochemical analysis of TNF-α expression in islets, we are able to show that the staining pattern of TNF-α resembles that of dendritic cells (DC) and macrophages (Mφ) rather than T cells and that TNF-α is expressed in islets at the very early stages of insulitis when no T cells are detected. On double staining for TNF-α and cell surface markers, we can demonstrate that TNF-α staining clearly correlates with DC and Mφ, whereas there is a poor correlation with T cells. This feature was observed at both early and late stages of insulitis. TNF-α expression was also seen in NOD-SCID islets, in addition to a peri-islet infiltration consisting of DC and Mφ, indicating that T cells are not required for the early DC and Mφ infiltration and TNF-α expression in islets. In conclusion, our results show that DC and Mφ are the major, early source of TNF-α in the NOD islet infiltrate and that TNF-α can be expressed independently of T cells, indicating that the early DC and Mφ infiltration and expression of TNF-α are crucial in initiation of diabetes.