Biomedical subjects

Dwight H Kono

Publications and source records attributed to Dwight H Kono.

15 recordsLinked to original sources

PubMed2006

Genetics of SLE in mice.

Genetic studies in spontaneous, induced, and gene-manipulated mouse models of SLE have provided significant insights into the potential number and diversity of genes that can promote, resist, and modify lupus susceptibility. Novel genes and mechanisms of disease pathogenesis have also been identified. Importantly, mouse models have provided an initial view of the genomic landscape of lupus-affecting genes, and have documented the complexities of verifying and determining the role of specific candidate loci and genes. Mouse models of lupus should continue to serve as a vital approach to defining the genetics of SLE.

Animals↗

PubMed2006

Paucity of V-D-D-J rearrangements and VH replacement events in lupus prone and nonautoimmune TdT-/- and TdT+/+ mice.

CDR3 regions containing two D segments, or containing the footprints of V(H) replacement events, have been reported in both mice and humans. However, the 12-23 bp rule for V(D)J recombination predicts that D-D rearrangements, which would occur between 2 recombination signal sequences (RSSs) with 12-bp spacers, should be extremely disfavored, and the cryptic RSS used for V(H) replacement is very inefficient. We have previously shown that newborn mice, which lack TdT due to the late onset of its expression, do not contain any CDR3 with D-D rearrangements. In the present study, we test our hypothesis that most D-D rearrangements are due to fortuitous matching of the second apparent D segment by TdT-introduced N nucleotides. We analyzed 518 sequences from adult MRL/lpr- and C57BL/6 TdT-deficient B cell precursors and found only two examples of CDR3 with D-D rearrangements and one example of a potential V(H) replacement event. We examined rearrangements from pre-B cells, marginal zone B cells, and follicular B cells from mice congenic for the Lbw5 (Sle3/5) lupus susceptibility loci and from other strains of mice and found very few examples of CDR3 with D-D rearrangements. We assayed B progenitor cells, and cells enriched for receptor editing, for DNA breaks at the "cryptic heptamer" but such breaks were rare. We conclude that many examples of apparent D-D rearrangements in the mouse are likely due to N additions that fortuitously match short stretches of D genes and that D-D rearrangements and V(H) replacement are rare occurrences in the mouse.

Animals↗

PubMed2005

Autoimmune alterations induced by the New Zealand Black Lbw2 locus in BWF1 mice.

The New Zealand Black (NZB) Lbw2 locus (lupus NZB x New Zealand White (NZW) 2 locus) was previously linked to mortality and glomerulonephritis, but not to IgG autoantibodies, suggesting that it played a role in a later disease stage. To define its contribution, (NZB x NZW)F1 hybrids (BWF1) containing two, one, or no copies of this locus were generated. Lack of the NZB Lbw2 indeed reduced mortality and glomerulonephritis, but not serum levels of total and anti-DNA IgG Abs. There were, however, significant reductions in the B cell response to LPS, total and anti-DNA IgM and IgG Ab-forming cells, IgM Ab levels, and glomerular Ig deposits. Furthermore, although serum IgG autoantibody levels correlated poorly with kidney IgG deposits, the number of spontaneous IgG Ab-forming cells had a significant correlation. Genome-wide mapping of IgM anti-chromatin levels identified only Lbw2, and analysis of subinterval congenics tentatively reduced Lbw2 to approximately 5 Mb. Because no known genes associated with B cell activation and lupus are in this interval, Lbw2 probably represents a novel B cell activation gene. These findings establish the importance of Lbw2 in the BWF1 hybrid and indicate that Lbw2, by enhancing B cell hyperactivity, promotes the early polyclonal activation of B cells and subsequent production of autoantibodies.

Animals↗

PubMed2005

Immunology and genetics of induced systemic autoimmunity.

Systemic lupus erythematosus is a multigenic disorder of unknown etiology. To investigate the role of specific genes in lupus, we have examined the effects of single gene deletions on mercury-induced autoimmunity. Deficiency of certain genes abrogated induction of autoimmunity, while absence of others had little effect. The most interesting observations were obtained with genes related to interferon-gamma. Genes involved in upregulation of IFN-gamma expression did not significantly influence autoimmunity whereas absence of IFN-gamma or IFN-gamma receptor led to greatly reduced autoantibody responses and immunopathology. Absence of IRF-1, a gene expressed in response to IFN-gamma, resulted in selective retention of anti-chromatin autoantibodies demonstrating that specific defects in signaling pathways and gene expression subsequent to IFN-gamma/IFN-gamma receptor interaction influence specific disease parameters. These studies show that single gene deletions can have various outcomes ranging from no effect, suppression of one or more features of disease, to suppression of all features of disease, and that all three outcomes can be observed in the IFN-gamma pathway. IFN-gamma influences the expression and function of other lupus relevant genes such as IL-6 and beta2microglobulin, therefore the effects of these gene deletions on disease expression may also reflect responses downstream of IFN-gamma function.

Animals↗

PubMed2005

Interferons as pathogenic effectors in autoimmunity.

Interferons (IFNs) type-1 (IFN alpha/beta) and type-II (IFN-gamma) are the most pleiotropic molecules in the intricate cytokine network. This dominance arises from three crucial factors: (i) initiation of IFN-alpha/beta and IFN-gamma production at the inception of most innate immune responses, which primes for the ensuing adaptive immune responses, primarily through the sine qua non upregulation of major histocompatibility complex and costimulatory molecules; (ii) magnification of their production and signaling by cross-talk between themselves, and synergistic or antagonistic effects on other cytokines; and (iii) direct or indirect initiation of transcription of hundreds of immunologically relevant genes. Considering that aberrant immune responses against self-molecules seem to depend on the same constituents and pathways as those against exogenous antigens, it follows that IFNs are also major effectors in the pathogenesis of autoimmunity. Here, we review the diverse biological effects of IFNs on the immune system, discuss findings pertaining to the nature of exogenous and endogenous stimuli that might induce IFN production through the engagement of Toll-like receptors, and summarize the detrimental and, in some instances, beneficial effects of IFNs in systemic and organ-specific autoimmune diseases.

Animals↗

PubMed2005

Type I interferons (alpha/beta) in immunity and autoimmunity.

The significance of type I interferons (IFN-alpha/beta) in biology and medicine renders research on their activities continuously relevant to our understanding of normal and abnormal (auto) immune responses. This relevance is bolstered by discoveries that unambiguously establish IFN-alpha/beta, among the multitude of cytokines, as dominant in defining qualitative and quantitative characteristics of innate and adaptive immune processes. Recent advances elucidating the biology of these key cytokines include better definition of their complex signaling pathways, determination of their importance in modifying the effects of other cytokines, the role of Toll-like receptors in their induction, their major cellular producers, and their broad and diverse impact on both cellular and humoral immune responses. Consequently, the role of IFN-alpha/beta in the pathogenesis of autoimmunity remains at the forefront of scientific inquiry and has begun to illuminate the mechanisms by which these molecules promote or inhibit systemic and organ-specific autoimmune diseases.

Adaptation, Physiological↗

PubMed2004

Costimulation requirements of induced murine systemic autoimmune disease.

Costimulation between T cells and APC is required for productive immune responses. A number of receptor/ligand pairs have been shown to mediate costimulation, including CD28/B7 molecules (CD80 and CD86), CD40/CD40 ligand (CD40L, CD154), and LFA-1 (CD18)/ICAM-1 (CD54). T-B cell costimulation also plays a significant role in autoimmune diseases such as systemic lupus erythematosus. Murine HgCl2-induced autoimmunity (mHgIA) is a T cell-dependent systemic autoimmune disease that shares a number of common pathogenic mechanisms with idiopathic lupus. In this report, the significance of costimulation in mHgIA is examined by attempting to induce disease in mice deficient in either CD40L, CD28, or ICAM-1. Unlike absence of ICAM-1, homozygous deficiencies in either CD40L or CD28 significantly reduced the development of mHgIA. CD40L displayed a gene dosage effect as heterozygous mice also showed reduction of autoantibody responses and immunopathology. Markers of T cell activation such as CD44 and CTLA-4 were associated with disease expression in wild-type and ICAM-1-deficient mice but not in CD40L- or CD28-deficient mice. Absence of CTLA-4 expression in CD40L-/- mice suggests that signaling via both CD28 and CD40L is important for T cell activation and subsequent autoimmunity in mHgIA. Attempts to circumvent the absence of CD40L by increasing CD28 signaling via agonistic Ab failed to elicit CTLA-4 expression. These findings indicate that breaking of self-tolerance in mHgIA requires signaling via both the CD28/B7 and CD40/CD40L pathways.

Animals↗

PubMed2004

Terminal deoxynucleotidyltransferase deficiency decreases autoimmune disease in diabetes-prone nonobese diabetic mice and lupus-prone MRL-Fas(lpr) mice.

The wide diversity of the T and B Ag receptor repertoires becomes even more extensive postneonatally due to the activity of TdT, which adds nontemplated N nucleotides to Ig and TCR coding ends during V(D)J recombination. In addition, complementarity-determining region 3 sequences formed in the absence of TdT are more uniform due to the use of short sequence homologies between the V, D, and J genes. Thus, the action of TdT produces an adult repertoire that is both different from, and much larger than, the repertoire of the neonate. We have generated TdT-deficient nonobese diabetic (NOD) and MRL-Fas(lpr) mice, and observed a decrease in the incidence of autoimmune disease, including absence of diabetes and decreased pancreatic infiltration in NOD TdT(-/-) mice, and reduced glomerulonephritis and increased life span in MRL-Fas(lpr) TdT(-/-) mice. Using tetramer staining, TdT(-/-) and TdT(+/+) NOD mice showed similar frequencies of the diabetogenic BDC 2.5 CD4(+) T cells. We found no increase in CD4(+)CD25(+) regulatory T cells in NOD TdT(-/-) mice. Thus, TdT deficiency ameliorates the severity of disease in both lupus and diabetes, two very disparate autoimmune diseases that affect different organs, with damage conducted by different effector cell types. The neonatal repertoire appears to be deficient in autoreactive T and/or B cells with high enough affinities to induce end-stage disease. We suggest that the paucity of autoreactive specificities created in the N region-lacking repertoire, and the resultant protection afforded to the newborn, may be the reason that TdT expression is delayed in ontogeny.

Animals↗

PubMed2004

Deficiency of the cyclin kinase inhibitor p21(WAF-1/CIP-1) promotes apoptosis of activated/memory T cells and inhibits spontaneous systemic autoimmunity.

A characteristic feature of systemic lupus erythematosus is the accumulation of activated/memory T and B cells. These G0/G1-arrested cells express high levels of cyclin-dependent kinase inhibitors such as p21, are resistant to proliferation and apoptosis, and produce large amounts of proinflammatory cytokines. Herein, we show that ablation of p21 in lupus-prone mice allows these cells to reenter the cell cycle and undergo apoptosis, leading to autoimmune disease reduction. Absence of p21 resulted in enhanced Fas/FasL-mediated activation-induced T cell death, increased activation of procaspases 8 and 3, and loss of mitochondrial transmembrane potential. Increased apoptosis was also associated with p53 up-regulation and a modest shift in the ratio of Bax/Bcl-2 toward the proapoptotic Bax. Proliferation and apoptosis of B cells were also increased in p21-/- lupus mice. Thus, modulation of the cell cycle pathway may be a novel approach to reduce apoptosis-resistant pathogenic lymphocytes and to ameliorate systemic autoimmunity.

Animals↗

PubMed2003

Genetic complementation in female (BXSB x NZW)F2 mice.

F(1) hybrids among New Zealand Black (NZB), New Zealand White (NZW), and BXSB lupus-prone strains develop accelerated autoimmunity in both sexes regardless of the specific combination. To identify BXSB susceptibility loci in the absence of the Y chromosome accelerator of autoimmunity (Yaa) and to study the genetics of this complementation, genome-wide quantitative trait locus (QTL) mapping was performed on female (BXSB x NZW)F(2) mice. Six QTL were identified on chromosomes 1, 4, 5, 6, 7, and 17. Survival mapped to chromosomes 5 and 17, anti-chromatin Ab to chromosomes 4 and 17, glomerulonephritis to chromosomes 6 and 17, and splenomegaly to chromosomes 1, 7, and 17. QTL on chromosomes 4 and 6 were new and designated as Lxw1 and -2, respectively. Two non-MHC QTL (chromosomes 1 and 4) were inherited from the BXSB and the rest were NZW-derived, including two similar to previously defined loci. Only two of 11 previously defined non-MHC BXSB QTL using male (Yaa(+)) crosses were implicated, suggesting that some male-defined BXSB QTL may require coexpression of the Yaa. Findings from this and other studies indicate that BXSB and NZB backgrounds contribute completely different sets of genes to complement NZW mice. Identification of susceptibility genes and complementing genes in several lupus-prone strain combinations will be important for defining the epistatic effects and background influences on the heterogeneous genetic factors responsible for lupus induction.

Animals↗

PubMed2003

Type-I interferon receptor deficiency reduces lupus-like disease in NZB mice.

Indirect evidence suggests that type-I interferons (IFN-alpha/beta) play a significant role in the pathogenesis of lupus. To directly examine the contribution of these pleiotropic molecules, we created congenic NZB mice lacking the alpha-chain of IFN-alpha/betaR, the common receptor for the multiple IFN-alpha/beta species. Compared with littermate controls, homozygous IFN-alpha/betaR-deleted NZB mice had significantly reduced anti-erythrocyte autoantibodies, erythroblastosis, hemolytic anemia, anti-DNA autoantibodies, kidney disease, and mortality. These reductions were intermediate in the heterozygous-deleted mice. The disease-ameliorating effects were accompanied by reductions in splenomegaly and in several immune cell subsets, including B-1 cells, the major producers of anti-erythrocyte autoantibodies. Decreases of B and T cell proliferation in vitro and in vivo, and of dendritic cell maturation and T cell stimulatory activity in vitro were also detected. Absence of signaling through the IFN-alpha/betaR, however, did not affect increased basal levels of the IFN-responsive p202 phosphoprotein, encoded by a polymorphic variant of the Ifi202 gene associated with the Nba2 predisposing locus in NZB mice. The data indicate that type-I IFNs are important mediators in the pathogenesis of murine lupus, and that reducing their activity in the human counterpart may be beneficial.

Animals↗

PubMed2003

Inhibition of lupus by genetic alteration of the interferon-alpha/beta receptor.

Type I interferons (IFN-alphabeta) are immunoregulatory cytokines that promote both innate and adaptive immune responses. Although they have been implicated in human SLE, recent studies in mice have helped solidify this connection. By using lupus-prone mice with knockout of the IFN-alphabeta receptor, we and others have documented that lack of IFN-alphabeta leads to a marked reduction in disease manifestations, including autoantibody production, target organ damage and mortality. Furthermore, IFN-alphabeta was found to potentially contribute to several levels of disease pathogenesis. These included the differentiation and activation of dendritic cells, the activation and proliferation of T cells, T cell survival and the activation and survival of autoantibody-producing B cells. These findings strongly support the targeting of IFN-alphabeta in SLE and suggest that definition of the specific pathways critical for disease induction will be important for optimal intervention.

Animals↗

PubMed2003

Using single-gene deletions to identify checkpoints in the progression of systemic autoimmunity.

Systemic lupus erythematosus is a multigenic disorder of unknown etiology. To investigate the roles that specific genes play in lupus, we have examined the disease profiles in mice with single-gene deletions. In total, some 17 genes have been studied. Absence of certain genes, such as CD40L, CD28, or Igh6, abrogated induction of autoimmunity. Other genes, such as Igh5, IL-4, or ICAM-1, had little effect on the development of disease. Intermediate effects were observed in IL-6-deficient mice, while absence of beta2-microglobulin resulted in loss of hypergammaglobulinemia and IgG1 autoantibodies, but produced little change in anti-chromatin antibodies or glomerular deposits. The most interesting observations were obtained with genes related to the expression or function of interferon-gamma (IFN-gamma). Reductions in IFN-gamma levels in murine lupus are associated with reductions in both autoantibody levels and immune-complex- mediated pathology. Genes involved in up-regulation of IFN-gamma expression, such as IL-12, STAT-4, or ICE, did not significantly influence autoimmunity, whereas absence of IFN-gamma or IFN-gamma receptor led to greatly reduced autoantibody response and immunopathology. Absence of IRF-1, a gene ex-pressed in response to IFN-gamma, resulted in selective retention of anti-chromatin antibodies but little glomerular pathology. These studies suggest that the presence of a baseline level of IFN-gamma, rather than increased expression, is important for autoimmunity. Furthermore, as the IRF-1 knockout demonstrates, specific defects in signaling pathways and gene expression subsequent to IFN-gamma/IFN-gamma receptor interaction may influence only certain disease parameters. It has not escaped our attention that IFN-gamma influences the expression and function of other immunologically relevant genes, such as IL-4, IL-6, and beta2-microglobulin. Thus, these genes may be part of the downstream events following IFN-gamma/IFN-gamma receptor interaction that promote the development of autoimmunity.

Animals↗

PubMed2002

Histidine-rich glycoprotein binds to DNA and Fc gamma RI and potentiates the ingestion of apoptotic cells by macrophages.

Histidine-rich glycoprotein (HRG) is an abundant serum protein that exhibits many functions in diverse biological systems. In this study, we show that HRG potentiates the ingestion of apoptotic cells by mature human monocyte-derived macrophages (HMDM). HRG bound specifically to apoptotic Jurkat cells and mature HMDM in a saturable and concentration-dependent manner. Purified HRG or HRG in sera increased the number of HMDM-containing apoptotic cells and accelerated the ingestion, while neutralization or depletion of HRG from sera reduced this effect. Anti-FcgammaRI mAb inhibited HRG binding to HMDM, while DNA, but not chromatin, inhibited HRG binding to apoptotic cells, and either anti-FcgammaRI or DNA abrogated the HRG-dependent ingestion. The findings indicate that HRG, by acting as a bridge between DNA on apoptotic cells and FcgammaRI on HMDM, is a key physiological mediator of apoptotic cell clearance by macrophages.

Adjuvants, Immunologic↗

PubMed2002

Deletion of p21 (WAF-1/Cip1) does not induce systemic autoimmunity in female BXSB mice.

Cell cycle, apoptosis, and replicative senescence are all influenced by the cyclin-dependent kinase inhibitor, p21. It was previously reported that deletion of p21 in 129/Sv x C57BL/6 mixed genetic background mice induced a severe lupus-like disease, almost exclusively in females. However, we did not confirm this finding in an independently derived stock of 129/Sv x C57BL/6 p21(-/-) mice. To further address this discrepancy, we examined the effects of p21 deletion in BXSB female mice that develop late-life, mild lupus-like disease. Survival, polyclonal Igs, anti-chromatin Abs, and kidney histopathology in these mice were unremarkable and identical to wild-type littermates for up to 14 mo of age. We conclude that p21 deficiency does not promote autoimmunity even in females of a predisposed strain. The findings indicate that the use of mixed background 129/Sv x C57BL/6 mice to study effects of gene deletions in systemic autoimmunity may be confounded by the genetic heterogeneity of this cross. We suggest that studies addressing gene deletion effects in systemic autoimmunity should use sufficiently backcrossed mice to attain genetic homogeneity, include wild-type littermate controls, and preferentially use congenic inbred strains with late-life lupus predisposition to emulate the polygenic nature of this disease.

Animals↗