Felicia Gaskin

A Major Lung CD103 (αE)-β7 Integrin-Positive Epithelial Dendritic Cell Population Expressing Langerin and Tight Junction Proteins

Dendritic cells (DC) mediate airway Ag presentation and play key roles in asthma and infections. Although DC subsets are known to perform different functions, their occurrence in mouse lungs has not been clearly defined. In this study, three major lung DC populations have been found. Two of them are the myeloid and plasmacytoid DC (PDC) well-characterized in other lymphoid organs. The third and largest DC population is the integrin αE (CD103) β7-positive and I-AhighCD11chigh-DC population. This population was found to reside in the lung mucosa and the vascular wall, express a wide variety of adhesion and costimulation molecules, endocytose avidly, present Ag efficiently, and produce IL-12. Integrin αEβ7+ DC (αE-DC) were distinct from intraepithelial lymphocytes and distinguishable from CD11bhigh myeloid and mPDCA-1+B220+Gr-1+ PDC populations in surface marker phenotype, cellular functions, and tissue localization. Importantly, this epithelial DC population expressed high levels of the Langerhans cell marker Langerin and the tight junction proteins Claudin-1, Claudin-7, and ZO-2. In mice with induced airway hyperresponsiveness and eosinophilia, αE-DC numbers were increased in lungs, and their costimulation and adhesion molecules were up-regulated. These studies show that αE-DC is a major and distinct lung DC population and a prime candidate APC with the requisite surface proteins for migrating across the airway epithelia for Ag and pathogen capture, transport, and presentation. They exhibit an activated phenotype in allergen-induced lung inflammation and may play significant roles in asthma pathogenesis.

Breaking Tolerance to Double Stranded DNA, Nucleosome, and Other Nuclear Antigens Is Not Required for the Pathogenesis of Lupus Glomerulonephritis

In lupus-prone NZM2328 mice, a locus Cgnz1 on chromosome 1 was linked to chronic glomerulonephritis, severe proteinuria, and early mortality in females. A locus Adnz1 on chromosome 4 was linked to antinuclear antibody (ANA) and anti–double stranded DNA (dsDNA) antibody (Ab) production. In this investigation, two congenic strains, NZM2328.C57L/Jc1 (NZM.C57Lc1) and NZM2328.C57L/Jc4 (NZM.C57Lc4), were generated by replacing the respective genetic intervals containing either Cgnz1 or Adnz1 with those from C57L/J, a nonlupus-prone strain. The NZM.C57Lc1 females had markedly reduced incidence of chronic glomerulonephritis and severe proteinuria. NZM.C57Lc4 females had chronic glomerulonephritis and severe proteinuria without circulating ANA, anti-dsDNA, and antinucleosome Ab. These data confirm the linkage analysis. Unexpectedly, NZM.C57Lc1 females had little anti-dsDNA and related Ab, suggesting the presence of a second locus Adnz2 on chromosome 1. The diseased NZM.C57Lc4 kidneys had immune complexes by immunofluorescence and electron microscopy. The eluates from these kidneys did not contain ANA, anti-dsDNA, and antinucleosome Ab, indicative of the presence of non–anti-dsDNA nephritogenic Ab. Thus, breaking tolerance to dsDNA and chromatin is not required for the pathogenesis of lupus nephritis. These results reaffirm that anti-dsDNA and related Ab production and chronic glomerulonephritis are under independent genetic control. These findings have significant implications in the pathogenesis of systemic lupus erythematosus.

P2X7 Blockade Attenuates Murine Lupus Nephritis by Inhibiting Activation of the NLRP3/ASC/Caspase 1 Pathway

OBJECTIVE The NLRP3 inflammasome plays key roles in inflammation and autoimmunity, and purinergic receptor P2X7 has been proposed to be upstream of NLRP3 activation. The aim of the present study, using murine models, was to investigate whether the P2X7 /NLRP3 inflammasome pathway contributes to the pathogenesis of lupus nephritis (LN). METHODS MRL/lpr mice were treated with the selective P2X7 antagonist brilliant blue G (BBG) for 8 weeks. Following treatment, the severity of renal lesions, production of anti-double-stranded DNA (anti-dsDNA) antibodies, rate of survival, activation of the NLRP3/ASC/caspase 1 inflammasome pathway, and ratio of Th17 cells to Treg cells were evaluated. P2X7 -targeted small interfering RNA (siRNA) was also used for in vivo intervention. Similar evaluations were carried out in NZM2328 mice, a model of LN in which the disease was accelerated by administration of adenovirus-expressing interferon-α (AdIFNα). RESULTS Significant up-regulation of P2X7 /NLRP3 inflammasome signaling molecules was detected in the kidneys of MLR/lpr mice as compared with normal control mice. Blockade of P2X7 activation by BBG suppressed NLRP3/ASC/caspase 1 assembly and the subsequent release of interleukin-1β (IL-1β), resulting in a significant reduction in the severity of nephritis and circulating anti-dsDNA antibodies. The lifespan of the treated mice was significantly prolonged. BBG treatment reduced the serum levels of IL-1β and IL-17 and the Th17:Treg cell ratio. Similar results were obtained by specific siRNA silencing of P2X7 in vivo. The effectiveness of BBG treatment in modulating LN was confirmed in NZM2328 mice with AdIFNα-accelerated disease. CONCLUSION Activation of the P2X7 signaling pathway accelerates murine LN by activating the NLRP3/ASC/caspase 1 inflammasome, resulting in increased IL-1β production and enhanced Th17 cell polarization. Thus, targeting of the P2X7 /NLRP3 pathway should be considered as a novel therapeutic strategy in patients with lupus.

Increased incidence of anti-β-amyloid autoantibodies secreted by Epstein-Barr virus transformed B cell lines from patients with Alzheimer's disease

During the past several years, evidence has been accumulated to support the thesis that immunological factors may play some role in Alzheimers disease (AD). We have characterized the reactive antigens detected by certain monoclonal antibodies secreted by Epstein-Barr virus (EBV)-transformed B cell lines from the peripheral blood of AD patients and controls. Autoantibodies against beta-amyloid protein beta-amyloid protein (beta-A) in amyloid plaques and blood vessels and in enzyme-linked immunosorbent assays (ELISA) have been reported in four cell lines derived from an AD patient. In this study, over 3300 EBV-transformed B cell lines from thirteen individuals were tested in ELISAs for antibodies against beta-A peptides. Significantly more autoantibodies against beta-A (1-40) were found in the AD group, 2.26 +/- 0.62% (39/1794 cell lines) than in the control group, 0.28 +/- 0.36% (5/1552 cell lines) with P < 0.005. These new antibodies did not react with plaques or amyloid deposits in blood vessels. In contrast to the four plaque-reactive autoantibodies which reacted better with beta-A (1-40) than with beta-A (1-28), 70% of these anti-beta-A (1-40) antibodies reacted as well or better with beta-A (1-28). Many of them were also reactive with beta-A (1-16). Tested against a panel of cytoskeletal proteins and Hela cells, many of these anti-beta-A (1-40) antibodies appear to be polyreactive. The higher incidence of anti-beta-A antibody secreting B cells in AD patients provides further evidence that autoimmunity may play a role in AD.

Ro60 peptides induce antibodies to similar epitopes shared among lupus-related autoantigens.

The coexistence of autoantibodies to ribonucleoproteins (RNP) in sera of patients with systemic lupus erythematosus has been attributed to intermolecular determinant spreading among physically associated proteins. Recently, we showed that murine Ab responses to rRo60 or Ro60 peptides were diversified unexpectedly to small nuclear RNP. In this investigation, the mechanisms for this autoantibody diversification were examined. Intramolecular determinant spreading was demonstrated in mice immunized with human or mouse Ro60316–335. Immune sera depleted of anti-peptide Ab immunoprecipitated Ro60-associated mY1 and mY3 RNA and remained reactive to a determinant on Ro60128–285. Absorption with the immunogen depleted the immune sera completely of anti-Golgi complex Ab (inducible only with human Ro60316–335) and anti-La Ab, and reduced substantially Ab to SmD and 70-kDa U1RNP. Mouse rRo60 completely inhibited the immune sera reactivity to La, SmD, and 70-kDa U1RNP. However, La, SmD, and 70-kDa U1RNP preferentially inhibited the antiserum reactivities to these Ags, respectively. Affinity-purified anti-La Ab were reactive with Ro60, La, SmD, and 70-kDa U1RNP. These results provide evidence that a population of the induced autoantibodies recognized determinants shared by these autoantigens. Lack of sequence homology between Ro60316–335 and La, SmD, or 70-kDa U1RNP suggests that these determinants are conformational. Interestingly, similar cross-reactive autoantibodies were found in NZB/NZW F1 sera. Thus, a single molecular mimic may generate Ab to multiple RNP Ags. Furthermore, cross-reactive determinants shared between antigenic systems that are not associated physically (Ro/La RNP and small nuclear RNP) may be important in the generation of autoantibody diversity in systemic lupus erythematosus.

Lupus Glomerulonephritis Revisited 2004: Autoimmunity and End-Organ Damage

Histopathology of the kidney and clinical presentation are critical factors in the diagnosis of immune‐mediated glomerulonephritis (GN). The histological manifestations of glomerular injury are shared by multiple underlying mechanisms. Work from our laboratory and from other investigators shows that antinuclear, antihistone or anti‐dsDNA antibodies are neither required nor sufficient for development of lupus GN. In addition, antibody to dsDNA can be generated by mechanisms other than loss of tolerance to chromatin. Genetic analyses demonstrate that although there is some interaction between autoantibody production and renal disease, the phenotypes are regulated by distinct genetic intervals. Furthermore, renal failure is not an essential outcome of the immune‐complex deposition and proliferative lupus GN. These data are also supported by published studies from systemic lupus erythematosus (SLE) patients. The immune regulation of lupus GN is distinct from other organ‐specific diseases and not influenced by CD25+ or NK1.1+ regulatory T cells. Thus, fatal GN may depend upon a kidney‐reactive T‐cell response that, in turn, may be regulated by gender and intrinsic end‐organ factors. The data discussed in this review call for a re‐evaluation of the current paradigms for pathogenesis of SLE. An interactive model separating autoimmunity from end‐organ susceptibility for the pathogenesis of SLE is proposed.

Genetics of systemic lupus erythematosus: immune responses and end organ resistance to damage

Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disorder. Considerable progress has been made to delineate the genetic control of this complex disorder. In this review, selected aspects of human and mouse genetics related to SLE are reviewed with emphasis on genes that contribute to both innate and adaptive immunity and to genes that contribute directly to susceptibility to end organ damage. It is concluded that the interactions among these two major pathways will provide further insight into the pathogenesis of SLE. An interactive model of the two major pathways is proposed without emphasis on the importance of breaking tolerance to autoantigens.

Severe Focal Sialadenitis and Dacryoadenitis in NZM2328 Mice Induced by MCMV: A Novel Model for Human Sjögren’s Syndrome

The genetic and environmental factors that control the development of Sjögren’s syndrome, an autoimmune disease mainly involving the salivary and lacrimal glands, are poorly understood. Viruses which infect the glands may act as a trigger for disease. The ability of sialotropic murine CMV (MCMV) to induce acute and chronic glandular disease was characterized in an autoimmune-prone mouse strain, NZM2328. MCMV levels were detectable in the salivary and lacrimal glands 14–28 days after i.p. infection and correlated with acute inflammation in the submandibular gland. After latency, virus was undetectable in the glands by PCR. At this stage, NZM2328 female mice developed severe chronic periductal inflammation in both submandibular and lacrimal glands in contrast to the much milder infiltrates found in female B6-lpr and male NZM2328. The focal infiltrates consisted of CD4+ and B220+ cells as opposed to diffuse CD4+, CD8+, and B220+ cells during acute infection. Salivary gland functional studies revealed a gender-specific progressive loss of secretory function between days 90 and 125 postinfection. Latent MCMV infection did not significantly affect the low incidence of autoantibodies to Ro/SSA and La/SSB Ags in NZM2328 mice. However, reactivities to other salivary and lacrimal gland proteins were readily detected. MCMV infection did not significantly alter the spontaneous onset of kidney disease in NZM2328. Thus, chronic inflammation induced by MCMV with decreased secretory function in NZM2328 mice resembles the disease manifestations of human Sjögren’s syndrome.

A novel role of IL-2 in organ-specific autoimmune inflammation beyond regulatory T cell checkpoint: both IL-2 knockout and Fas mutation prolong lifespan of Scurfy mice but by different mechanisms.

Mutation of the Foxp3 transcription factor in Scurfy (Sf) mice results in complete absence of the CD4+Foxp3+ regulatory T cells (Tregs), severe multiorgan autoimmune syndrome, and early death at 4 wk of age. However, Sf mice simultaneously bearing the Il2−/− (Sf.Il2−/−) or Faslpr/lpr gene (Sf.Faslpr/lpr) have extended lifespan despite totally lacking Tregs, indicating a role of IL-2 and CD95 (Fas) signaling pathways in the multiorgan autoimmune syndrome beyond the Treg checkpoint. IL-2 has been implicated in regulating lymphoproliferation and CD178 (FasL) expression. However, Sf.Il2−/− mice have increased lymphoproliferation and FasL expression. Importantly, the pattern of organ-specific autoimmune response of Sf.Il2−/−mice resembled IL-2 knockout mice whereas that of Sf.Faslpr/lpr was similar to Sf mice, indicating that the distinct and weakened autoimmune manifestation in IL-2 knockout mice was not caused by the residual Tregs. Our study demonstrated a novel role of IL-2 in regulating multiorgan autoimmune inflammation beyond the Treg checkpoint and indicated that both Il2−/− and Faslpr/lpr genes prolong the lifespan of Sf mice but by different mechanisms.

Myeloid-derived suppressor cells are proinflammatory and regulate collagen-induced arthritis through manipulating Th17 cell differentiation

Myeloid-derived suppressor cells (MDSC) and Th17 cells were found to expand in collagen-induced arthritis (CIA) significantly. Two subsets of MDSC, polymorphonuclear (PMN) and mononuclear (MO), were detected and their ratios varied during the development of CIA. The depletion of MDSC in vivo resulted in suppression of T-cell proliferation and decreased IL-17A and IL-1β production. The adoptive transfer of MDSC restored the severity of arthritis and Th17 cell differentiation. The depletion of MDSCs on day 35 resulted in arthritis amelioration without reaching a significant difference. Furthermore, MDSCs from CIA mice had higher production of IL-1β and promoted Th17 cell differentiation. The expansion of MDSCs in the peripheral blood of rheumatoid arthritis (RA) patients was in correlation with increased Th17 cells and disease activity DAS28. These results support the hypothesis that MDSC may play a significant proinflammatory role in the pathogenesis of CIA and RA by inducing Th17 development in an IL-1β-dependent manner.