Biomedical subjects

Argyrios N Theofilopoulos

Publications and source records attributed to Argyrios N Theofilopoulos.

At least 19 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↗

PubMed2006

Efficient T cell activation via a Toll-Interleukin 1 Receptor-independent pathway.

Here, we describe a previously unrecognized pathway for activation of antigen-specific adaptive immune responses that was independent of Toll-Interleukin 1 Receptor signaling and directed toward detection of antigens expressed by apoptotic cells. This pathway is represented within Flt-3 Ligand-derived dendritic cells (DCs) that represent immature lymphoid DCs, but not within GM-CSF-treated bone marrow-derived dendritic cells. Exposure of these DCs to apoptotic cells resulted in production of type I interferon and favored the development of cytotoxic T cell responses. The N-Ethyl-N-Nitrosourea-induced germline mutation 3d (Unc3b1(3d/3d)) abolished both MHC class I and II responses elicited by this pathway, whereas a null allele of Cd36 selectively abolished class II responses. We propose that this mode of adaptive immune activation evolved to permit the sensitive detection of intracellular microbial infections, particularly viral infections, which frequently induce apoptotic cell death, but may also be important in transplantation, autoimmunity, and vaccine development.

Animals↗

PubMed2006

Lack of intrinsic CTLA-4 expression has minimal effect on regulation of antiviral T-cell immunity.

CTLA-4 is considered one of the most potent negative regulators of T-cell activation. To circumvent experimental limitations due to fatal lymphoproliferative disease associated with genetic ablation of CTLA-4, we have used radiation chimeras reconstituted with a mixture of CTLA-4+/+ and CTLA-4-/- bone marrow that retain a normal phenotype and allow the evaluation of long-term T-cell immunity under conditions of intrinsic CTLA-4 deficiency. Following virus infection, we profiled primary, memory, and secondary CD8+ and CD4+ T-cell responses directed against eight different viral epitopes. Our data demonstrate unaltered antigen-driven proliferation, acquisition of effector functions, distribution of epitope hierarchies, T-cell receptor repertoire selection, functional avidities, and long-term memory maintenance in the absence of CTLA-4. Moreover, regulation of memory T-cell survival and homeostatic proliferation, as well as secondary responses, was equivalent in virus-specific CTLA4+/+ and CTL-A-4-/- T-cell populations. Thus, lack of CTLA-4 expression by antigen-specific T cells can be compensated for by extrinsic factors in the presence of CTLA-4 expression by other cells. These findings have implications for the physiologic, pathological, and therapeutic regulation of costimulation.

Animals↗

PubMed2005

Gamma delta T cell homeostasis is controlled by IL-7 and IL-15 together with subset-specific factors.

Among T cell subsets, gamma delta T cells uniquely display an Ag receptor-based tissue distribution, but what defines their preferential homing and homeostasis is unknown. To address this question, we studied the resources that control gamma delta T cell homeostasis in secondary lymphoid organs. We found that gamma delta and alpha beta T cells are controlled by partially overlapping resources, because acute homeostatic proliferation of gamma delta T cells was inhibited by an intact alpha beta T cell compartment, and both populations were dependent on IL-7 and IL-15. Significantly, to undergo acute homeostatic proliferation, gamma delta T cells also required their own depletion. Thus, gamma delta T cell homeostasis is maintained by trophic cytokines commonly used by other types of lymphoid cells, as well as by additional, as yet unidentified, gamma delta-specific factors.

Adoptive Transfer↗

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

Tumor immunity via homeostatic T cell proliferation: mechanistic aspects and clinical perspectives.

Efforts to develop effective anti-tumor immunotherapies are hampered by the difficulty of overcoming tolerance against tumor antigens, which in most instances are normal gene products that are over-expressed, preferentially expressed or re-expressed in cancer cells. Considering that lymphopenia-induced homeostatic T cell proliferation is mediated by self-peptide/MHC recognition and that the expanded cells acquire some effector functions, we hypothesized that this process could be used to break tolerance against tumor antigens. Studies by us and others in several mouse models demonstrated that availability of tumor antigens during homeostatic T cell proliferation indeed leads to effective anti-tumor autoimmunity with specificity and memory. This effect appears to be mediated by reduction in the activation threshold of low-affinity tumor-specific T cells, leading to their preferential engagement and expansion. In its simplicity, this approach is likely to have application in humans, since it relies on conventional lymphopenia-inducing cancer therapies, infusion of autologous lymphocytes and, optimally, tumor-specific vaccination.

Animals↗

PubMed2005

The new paradigm of T-cell homeostatic proliferation-induced autoimmunity.

In lymphopenic conditions, T cells expand to re-establish homeostasis by a process dependent on self-peptide-MHC recognition and the availability of proliferation- and survival-promoting cytokines. Although physiologically normal, chronic recurrence of this process might lead to selection of high-affinity self-reactive T-cell clones and autoimmune disease in susceptible individuals. A recent study in a diabetes-prone mouse model has provided strong evidence to support this hypothesis.

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

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↗

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↗

PubMed2002

Oligoclonal CD4(+) T cell expansions in lung transplant recipients with obliterative bronchiolitis.

Obliterative bronchiolitis (OB) is a dreaded and frequent complication of lung transplantation with a poorly understood immunopathogenesis. To further evaluate disease mechanisms, we used T cell antigen receptor (TCR) beta-chain variable region RNase protection assays, after polymerase chain reaction amplification of TCR cDNA, to quantitate circulating CD4(+) and CD8(+) repertoires of transplant recipients with OB or no evidence of rejection (NER). All six recipients with OB had markedly abnormal CD4 expansions (2.5 +/- 0.5 expansions/recipient) attributable to oligoclonal proliferations. Only two of six recipients with NER had a single, much lesser, CD4(+) abnormality each (p < 0.01). Moreover, one of these patients developed OB shortly thereafter, and the other NER abnormality may have predated transplantation. In contrast, CD8(+) expansions were common in both recipient populations. Findings of CD4(+) expansions had 100% sensitivity and 80% specificity for the presence or imminent development of OB. These data suggest proliferations of CD4(+) T cells are important in OB pathogenesis, and these are most likely part of a major histocompatibility complex Class II-dependent process of indirect alloantigen presentation. These CD4(+) clones are likely to have facultative helper functions for the multiple and diverse immune processes that have been implicated in OB. Furthermore, the close association of CD4(+) expansions with OB raises possibilities of development of novel diagnostic and therapeutic approaches.

Adult↗