V(D)J recombination in peritoneal B cells of leaky scid mice

Exploring Colitis through Dynamic T Cell Adoptive Transfer Models

Numerous animal models of colitis have provided important insights into the pathogenesis of inflammatory bowel disease (IBD), contributing to a better understanding of the underlying mechanisms for IBD. As aberrant CD4+ T cell responses play a critical role in the pathogenesis and development of IBD, T cell adoptive transfer models of colitis have become a valuable tool in investigating the immunopathogenesis of intestinal inflammation. While the adoptive transfer of CD4+ CD45RBhi T cells into immunedeficient recipient mice was the first discovered and is currently the most widely used model, several variations of the T cell transfer model have also been developed with distinct features. Here, we describe the history, principle, and characteristics of adoptive transfer colitis models and discuss their strengths, limitations, and applications.

Combination Therapy of an Antibody Specific for Transferrin Receptor 1 (ch128.1/IgG1) With Bortezomib or Lenalidomide Results in Increased Survival in an In Vivo Model of Human Multiple Myeloma: A Brief Communication

Transferrin receptor 1 (TfR1) is a universal cancer marker and a meaningful target for antibody-based immunotherapy. We previously developed a mouse/human chimeric antibody (ch128.1/IgG1) specific for the human TfR1 and reported that treatment of SCID-Beige mice bearing disseminated human multiple myeloma (MM) cells with ch128.1/IgG1 results in significant antitumor activity in early-stage and late-stage disease. Both bortezomib and lenalidomide are Food and Drug Administration (FDA) approved therapeutics used to treat MM in combination with other agents. Since combining treatments with different mechanisms of action is an effective antitumor strategy and given the relevance of bortezomib and lenalidomide in MM therapy, we decided to explore, for the first time, the combination of bortezomib or lenalidomide treatment with ch128.1/IgG1 within the context of late-stage MM disease. We found that treatment with a single dose of ch128.1/IgG1, or multiple doses of bortezomib or lenalidomide, used as single agents, results in significant antitumor activity in SCID-Beige mice bearing late-stage disseminated human MM.1S tumors. However, this antitumor activity is superior when ch128.1/IgG1 is combined with either bortezomib or lenalidomide, showing significantly longer survival compared with any therapy used alone. These novel results suggest that the combinations of ch128.1/IgG1 and bortezomib or lenalidomide are promising strategies against MM.

The development of human immune system mice and their use to study tolerance and autoimmunity

Autoimmune diseases evolve from complex interactions between the immune system and self-antigens and involve several genetic attributes, environmental triggers and diverse cell types. Research using experimental mouse models has contributed key knowledge on the mechanisms that underlie these diseases in humans, but differences between the mouse and human immune systems can and, at times, do undermine the translational significance of these findings. The use of human immune system (HIS) mice enables the utility of mouse models with greater relevance for human diseases. As the name conveys, these mice are reconstituted with mature human immune cells transferred directly from peripheral blood or via transplantation of human hematopoietic stem cells that nucleate the generation of a complex human immune system. The function of the human immune system in HIS mice has improved over the years with the stepwise development of better models. HIS mice exhibit key benefits of the murine animal model, such as small size, robust and rapid reproduction and ease of experimental manipulation. Importantly, HIS mice also provide an applicable in vivo setting that permit the investigation of the physiological and pathological functions of the human immune system and its response to novel treatments. With the gaining popularity of HIS mice in the last decade, the potential of this model has been exploited for research in basic science, infectious diseases, cancer, and autoimmunity. In this review we focus on the use of HIS mice in autoimmune studies to stimulate further development of these valuable models.

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Human immune system (HIS) mice bear components of the human immune system.

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HIS mice engraft with human blood or hematopoietic stem cells, and sometimes thymus.

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HIS mice are used to investigate development and function of the human immune system.

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Immunological tolerance and autoimmune responses can be studied in HIS mice.

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HIS models of autoimmunity vary in complexity and in ability to represent disease.

Immune-relevant aspects of murine models of head and neck cancer

Head and neck cancers (HNCs) cause significant mortality and morbidity. There have been few advances in therapeutic management of HNC in the past 4 to 5 decades, which support the need for studies focusing on HNC biology. In recent years, increased recognition of the relevance of the host response in cancer progression has led to novel therapeutic strategies and putative biomarkers of tumor aggressiveness. However, tumor-immune interactions are highly complex and vary with cancer type. Pre-clinical, in vivo models represent an important and necessary step in understanding biological processes involved in development, progression and treatment of HNC. Rodents (mice, rats, hamsters) are the most frequently used animal models in HNC research. The relevance and utility of information generated by studies in murine models is unquestionable, but it is also limited in application to tumor-immune interactions. In this review, we present information regarding the immune-specific characteristics of the murine models most commonly used in HNC research, including immunocompromised and immunocompetent animals. The particular characteristics of xenograft, chemically induced, syngeneic, transgenic, and humanized models are discussed in order to provide context and insight for researchers interested in the in vivo study of tumor-immune interactions in HNC.

Exploring the Immunopathogenesis of Viral Hemorrhagic Fever in Mice with a Humanized Immune System

Viral hemorrhagic fever (VHF) as a disease entity was first codified in the 1930s by soviet scientists investigating patients suffering from hantavirus infection. The group of hemorrhagic fever viruses (HFVs) has since expanded to include members from at least four different virus families: Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae, all enveloped single-stranded RNA viruses. After infection, the natural hosts of HFVs do not develop symptoms, whereas humans can be severely affected. This observation and other evidence from experimental data suggest that the human immune system plays a crucial role in VHF pathogenesis. For this reason mice with a human immune system, referred to here as humanized mice (humice), are valuable tools that provide insight into disease mechanisms and allow for preclinical testing of novel vaccinations approaches as well as antiviral agents. In this article, we review the impact of humice in VHF research.

Antigen receptor editing in anti-DNA transitional B cells deficient for surface IgM

In response to encounter with self-Ag, autoreactive B cells may undergo secondary L chain gene rearrangement (receptor editing) and change the specificity of their Ag receptor. Knowing at what differentiative stage(s) developing B cells undergo receptor editing is important for understanding how self-reactive B cells are regulated. In this study, in mice with Ig transgenes coding for anti-self (DNA) Ab, we report dsDNA breaks indicative of ongoing secondary L chain rearrangement not only in bone marrow cells with a pre-B/B cell phenotype but also in immature/transitional splenic B cells with little or no surface IgM (sIgM(-/low)). L chain-edited transgenic B cells were detectable in spleen but not bone marrow and were still found to produce Ab specific for DNA (and apoptotic cells), albeit with lower affinity for DNA than the unedited transgenic Ab. We conclude that L chain editing in anti-DNA-transgenic B cells is not only ongoing in bone marrow but also in spleen. Indeed, transfer of sIgM(-/low) anti-DNA splenic B cells into SCID mice resulted in the appearance of a L chain editor (Vlambdax) in the serum of engrafted recipients. Finally, we also report evidence for ongoing L chain editing in sIgM(low) transitional splenic B cells of wild-type mice.

Growth, differentiation, and malignant transformation of pre-B cells mediated by inducible activation of v-Abl oncogene

The nonreceptor tyrosine kinase, encoded by the v-Abl oncogene of Abelson murine leukemia virus induces transformation of progenitor B cells. The v-Abl oncogene promotes cell cycle progression and inhibits pre-B cell differentiation. The temperature-sensitive form of Abelson murine leukemia virus offers a reversible model to study the role of v-Abl in regulating growth and differentiation. Inactivation of v-Abl elevates p27 and Foxo3a levels and activates NF-kappaB/Rel, which leads to G1 arrest and induction of Ig L chain gene rearrangement, respectively. In turn, v-Abl reactivation reduces p27 and Foxo3a levels, thus permitting G1-arrested cells to reenter the cell cycle. However, the cell lines derived from SCID mice that are defective in the catalytic subunit of DNA-dependent protein kinase retain elevated levels of p27 and Foxo3a proteins despite reactivation of v-Abl. Consequently, these cells are locked in the G1 phase for an extended period of time. The few cells that manage to bypass the G1 arrest become tumorigenic and fail to undergo pre-B cell differentiation induced by v-Abl inactivation. Deregulation of p27, Foxo3a, c-myc, and NF-kappaB/Rel was found to be associated with the malignant transformation of SCID temperature-sensitive form of Abelson murine leukemia virus pre-B cells.

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.

Pathways of removal of free DNA vector ends in normal and DNA-PKcs-deficient SCID mouse hepatocytes transduced with rAAV vectors

Elucidation of the mechanisms of transformation of single-stranded (ss) recombinant adeno-associated virus (rAAV) vector genomes into a variety of stable double-stranded (ds) forms is key to a complete understanding of rAAV vector transduction in vivo. Ds monomer genome formation and cellular ds DNA break (DSB) repair pathways that remove free vector ends toxic to cells, presumably play a central role in this process. By delivering rAAV and naked ds linear DNA vectors into livers of DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-deficient severe combined immunodeficiency (SCID) and wild-type mice, we demonstrate the presence of three major pathways for free ds vector end removal: (1) DNA-PKcs-dependent self-circularization, (2) DNA-PKcs-independent self-circularization, and (3) DNA-PKcs-independent concatemerization. By using the DNA-PKcs-independent pathways, mouse hepatocytes efficiently removed free ds rAAV vector ends even in the absence of DNA-PKcs. Our studies suggest a hierarchical organization of these processes; self-circularization is the preferred pathway over concatemerization, although the former has a limited capacity to remove free vector ends. These studies shed new light on the molecular mechanisms of rAAV vector transduction in vivo.

Age-dependent increase of peritoneal B-1b B cells in SCID mice

The impact of increasing age upon immunoglobulin production and B-lymphocyte generation in "leaky" severe combined immune-defective (SCID) mice was examined by enzyme-linked immunosorbent assay and flow cytometry. By 1 year of age, the mice had normal numbers of B cells in their peritoneal cavity, while their spleen had very few immunoglobulin M-positive (IgM+) cells. The majority of B cells expressed the CD11b marker characteristic of the B-1b subset. B-1a (CD5+) cells were present at a lower frequency and B-2 cells were absent. The frequency of mice producing detectable immunoglobulin increased with age, and isotype diversity within individual mice was variable. IgM production was most frequently observed followed by IgG3 and IgG2a, then IgG1, and finally IgA. The selective persistence of the B-1 B-cell subset in the peritoneal cavity of aging SCID mice is a natural model for the study of those genetic and environmental influences that determine lymphocyte longevity.

Development and function of diabetogenic T-cells in B-cell-deficient nonobese diabetic mice

Insulin-dependent diabetes (type 1 diabetes) in the NOD mouse is a T-cell-mediated autoimmune disease. However, B-cells may also play a critical role in disease pathogenesis, as genetically B-cell-deficient NOD mice (NOD.microMT) have been shown to be protected from type 1 diabetes and to display reduced responses to certain islet autoantigens. To examine the requirements for B-cells in the development of type 1 diabetes, we generated a B-cell-naive T-cell repertoire by transplantation of NOD fetal thymuses (FTs) into NOD.scid recipients. Surprisingly, these FT-derived NOD T-cells were diabetogenic in 36% of NOD.scid recipients, despite the absence of B-cells. In addition, T-cells isolated from NOD.microMT mice were diabetogenic in 22% of NOD.scid recipients. Together, these results indicate that B-cells are not an absolute requirement for the generation or effector function of an islet-reactive T-cell repertoire in NOD mice. We suggest that conditions favoring rapid lymphocyte expansion can reveal autoreactive T-cell activity and precipitate disease in genetically susceptible individuals.

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.

Gamma-Irradiation Directly Affects the Formation of Coding Joints in SCID Cell Lines

SCID mice have a defect in the catalytic subunit of the DNA-dependent protein kinase, causing increased sensitivity to ionizing radiation in all tissues and severely limiting the development of B and T cell lineages. SCID T and B cell precursors are unable to undergo normal V(D)J recombination: coding joint and signal joint products are less frequently formed and often will exhibit abnormal structural features. Paradoxically, irradiation of newborn SCID mice effects a limited rescue of T cell development. It is not known whether irradiation has a direct impact on the process of V(D)J joining, or whether irradiation of the thymus allows the outgrowth of rare recombinants. To investigate this issue, we sought to demonstrate an irradiation effect ex vivo. Here we have been able to reproducibly detect low-frequency coding joint products with V(D)J recombination reporter plasmids introduced into SCID cell lines. Exposure of B and T lineage cells to 100 cGy of gamma irradiation made no significant difference with respect to the number of coding joint and signal joint recombination products. However, in the absence of irradiation, the coding joints produced in SCID cells had high levels of P nucleotide insertion. With irradiation, markedly fewer P insertions were seen. The effect on coding joint structure is evident in a transient assay, in cultured cells, establishing that irradiation has an immediate impact on the process of V(D)J recombination. A specific proposal for how the DNA-dependent protein kinase catalytic subunit influences the opening of hairpin DNA intermediates during coding joint formation in V(D)J recombination is presented.

Balancing immunity and tolerance: deleting and tuning lymphocyte repertoires

Immunological self-tolerance is ensured by eliminating or inhibiting self-reactive lymphocyte clones, creating physical or functional holes in the B- and T-lymphocyte antigen receptor repertoires. The nature and size of these gaps in our immune defenses must be balanced against the necessity of mounting rapid immune responses to an everchanging array of foreign pathogens. To achieve this balance, only a fraction of particularly hazardous self-reactive clones appears to be physically eliminated from the repertoire in a manner that fully prevents their recruitment into an antimicrobial immune response. Many self-reactive cells are retained with a variety of conditional and potentially flexible restraints: (i) their ability to be triggered by antigen is diminished by mechanisms that tune down signaling by their antigen receptors, (ii) their ability to carry out inflammatory effector functions can be inhibited, and (iii) their capacity to migrate and persist is constrained. This balance between tolerance and immunity can be shifted, altering susceptibility to autoimmune disease and to infection by genetic or environmental differences either in the way antigens are presented, in the tuning molecules that adjust triggering set points for lymphocyte responses to antigen, or in the effector molecules that eliminate, retain, or expand particular clones.

Equine severe combined immunodeficiency: a defect in V(D)J recombination and DNA-dependent protein kinase activity

V(D)J rearrangement is the molecular mechanism by which an almost infinite array of specific immune receptors are generated. Defects in this process result in profound immunodeficiency as is the case in the C.B-17 SCID mouse or in RAG-1 (recombination-activating gene 1) or RAG-2 deficient mice. It has recently become clear that the V(D)J recombinase most likely consists of both lymphoid-specific factors and ubiquitously expressed components of the DNA double-strand break repair pathway. The deficit in SCID mice is in a factor that is required for both of these pathways. In this report, we show that the factor defective in the autosomal recessive severe combined immunodeficiency of Arabian foals is required for (i) V(D)J recombination, (ii) resistance to ionizing radiation, and (iii) DNA-dependent protein kinase activity.

Rescue of T cell-specific V(D)J recombination in SCID mice by DNA-damaging agents

Assembly of antigen receptor V (variable), D (diversity), and J (joining) gene segments requires lymphocyte-specific genes and ubiquitous DNA repair activities. Severe combined immunodeficient (SCID) mice are defective in general double-strand (ds) DNA break repair and V(D)J coding joint formation, resulting in arrested lymphocyte development. A single treatment of newborn SCID mice with DNA-damaging agents restored functional, diverse, T cell receptor beta chain coding joints, as well as development and expansion of thymocytes expressing both CD4 and CD8 coreceptors, but did not promote B cell development. Thymic lymphoma developed in all mice treated with DNA-damaging agents, suggesting an interrelation between V(D)J recombination, dsDNA break repair, and lymphomagenesis.

VH11 bias and normal V-D-J junctions in SCID B lymphocytes rescued by neonatal T cell transfer

The scid mutation interferes with normal rearrangement of antigen receptor genes, leading to an absence of T and B lymphocytes in most SCID mice. However, the SCID phenotype is "leaky", with an age- and strain-dependent increase in the incidence of mice with small number of T and B cells and readily detectable serum immunoglobulin. Introduction of neonatal T cells into young SCID mice results in a 100% incidence of the leaky phenotype. We have identified the location of antibody secreting cells in T cell-induced leaky SCID mice as the spleen and peritoneal cavity, and we have sequenced 35 productively rearranged immunoglobulin genes from these sites to determine if normal V-D-J recombination was occurring. VH11 sequences with potential autoreactivity were observed frequently in both the peritoneal cavity and spleen of T cell-induced leaky SCID mice, and these sequences were indistinguishable from those recovered from peritoneal cavity B cells from normal C.B-17 mice. Non-VH11 SCID sequences showed fewer N nucleotides and slightly more P nucleotides than normal V-D-J sequences. Many SCID junctions occurred at the site of short sequence homologies. These results suggest that successful V-D-J recombination is occurring with low frequency in all SCID mice, and that neonatal T cell transfer plus autoantigen stimulation allows the long term survival of these B cells.

Abnormal deletions in the T-cell receptor delta locus of mouse thymocytes

Separate genetic elements (V, D, and J) encode the variable regions of lymphocyte antigen receptors. During early lymphocyte differentiation, these elements rearrange to form contiguous coding segments (VJ and VDJ) for a diverse array of variable regions. Rearrangement is mediated by a recombinase that recognizes short DNA sequences (signals) flanking V, D, and J elements. Signals flank both the 5' and 3' sides of each D element, thereby allowing assembly of a functional VDJ gene. However, in rearrangements involving the D delta 2 and J delta 1 elements of the mouse T-cell receptor delta (TCR delta) locus, we unexpectedly found that the D delta 2 element and a portion of its 5' signal are often deleted. Approximately 50% of recovered D delta 2 to J delta 1 rearrangements from thymocytes of adult wild-type mice showed such deletions. An additional 20% of the rearrangements contained standard D delta 2-J delta 1 coding junctions but showed some loss of nucleotides from the 5' D delta 2 signal. This loss was clearly associated with another event involving a site-specific cleavage at the 5' signal/coding border of D delta 2 and rejoining of the modified signal and coding ends. The abnormal loss of D delta 2 and a portion of the 5' D delta 2 signal was infrequently observed in D delta 2-to-J delta 1 rearrangements recovered from neonatal mice. The possible basis and significance of this age-dependent phenomenon are discussed.

Abnormal deletions in the T-cell receptor delta locus of mouse thymocytes

Separate genetic elements (V, D, and J) encode the variable regions of lymphocyte antigen receptors. During early lymphocyte differentiation, these elements rearrange to form contiguous coding segments (VJ and VDJ) for a diverse array of variable regions. Rearrangement is mediated by a recombinase that recognizes short DNA sequences (signals) flanking V, D, and J elements. Signals flank both the 5' and 3' sides of each D element, thereby allowing assembly of a functional VDJ gene. However, in rearrangements involving the D delta 2 and J delta 1 elements of the mouse T-cell receptor delta (TCR delta) locus, we unexpectedly found that the D delta 2 element and a portion of its 5' signal are often deleted. Approximately 50% of recovered D delta 2 to J delta 1 rearrangements from thymocytes of adult wild-type mice showed such deletions. An additional 20% of the rearrangements contained standard D delta 2-J delta 1 coding junctions but showed some loss of nucleotides from the 5' D delta 2 signal. This loss was clearly associated with another event involving a site-specific cleavage at the 5' signal/coding border of D delta 2 and rejoining of the modified signal and coding ends. The abnormal loss of D delta 2 and a portion of the 5' D delta 2 signal was infrequently observed in D delta 2-to-J delta 1 rearrangements recovered from neonatal mice. The possible basis and significance of this age-dependent phenomenon are discussed.