doi:10.1016/j.clim.2008.03.328

Sa.108. CD47 Controls the In Vivo Proliferation andHomeostasis of Peripheral CD4+CD25+ Foxp3+Regulatory T Cells that Express CD103Vu Quang Van, Jinane Darwiche, Marianne Raymond, SylvieLesage, Salim Bouguermouh, Manuel Rubio, Marika Sarfati.Centre de Recherche de l'université de Montreal (CHUM),Montreal, QC, Canada

Peripheral CD103+Foxp3+ regulatory T cells (Tregs) candevelop both from conventional naïve T cells upon cognateAg delivery under tolerogenic conditions as well as fromthymic-derived, expanded/differentiated natural Tregs. Wehere show that CD47 expression, a marker of self onhematopoieitic cells, selectively regulated CD103+ Foxp3+Treg homeostasis at the steady state. We first observed arapid and progressive augmentation with age in theproportion of effector/memory-like (CD44HighCD62LLow)CD103+ Foxp3+ Tregs in CD47-deficient mice (CD47-/-) ascompared to age-matched wild type littermates. Yet,the proportion of quiescent (CD44LowCD62LHigh) CD103-Foxp3+ Tregs remained stable. We next found an increasedproliferation rate (BrdU incorporation) within theFoxp3+CD47-/-Tregs subpopulation that was restricted tothose expressing CD103. Finally, CD47-/-Tregs displayed anormal suppressive function in vitro and in vivo. We proposethat sustained CD47 expression throughout life is critical toavoid an excessive expansion/accumulation of CD103+Tregsthat may overwhelmingly inhibit pathogen or tumor-specificCTL responses.

doi:10.1016/j.clim.2008.03.329

Sa.109. Allelic and Phenotypic Heterogeneity at theAutoimmune Susceptibility Locus IL2RALisa Maier, Christopher Severson, Philip De Jager, DavidHafler. Harvard Medical School, Boston, MA

In a recent genome wide association scan for MS suscept-ibility genes, themost significant Single Nucleotide Polymorph-ism (SNP) outside the MHC associated with MS was located inthe gene encoding the alpha chain of the IL-2 receptorcomplex, IL2RA. The IL2RA gene has previously been associatedto Type 1 Diabetes (T1D) andGraves Disease,making it a sharedautoimmune susceptibility locus. In this study, we testedwhether, similarly to what was shown for the T1D variants, theMS susceptibility allele rs12722489 was associated with levelsof sIL-2RA. First, we quantitated serum levels of sIL-2RA andfound that they are increased in MS subjects compared tohealthy controls (mean sIL-2RA concentration in healthycontrols=2,022 pg/ml [95% CI 1,852 - 2,192]; mean sIL-2RAconcentrations in MS subjects=2,345 pg/ml [95% CI 2,256-2,435]; P=0.0001), an observation previously reported not onlyin MS but also in other autoimmune diseases, infectiousdiseases and malignancies. Using two independent serumcollections consisting of 70 healthy controls and 300 MS

patients, we then determined that the MS susceptibility alleleat rs12722489 is associatedwith increased levels of sIL-2RA in adose-dependent manner in both healthy controls (P=0.00019)and MS patients (P=0.0217). However, in stark contrast to thefinding for T1D susceptibility alleles, we found that the MSsusceptibility allele is associated with higher levels of sIL-2RA.Thus, MS susceptibility is associated with increased sIL-2RAlevels, while T1D susceptibility is associated with decreasedsIL-2RA levels.

doi:10.1016/j.clim.2008.03.330

Sa.110. Fully Human Monoclonal AntibodiesDirected Against Human LIGHT Effectively SuppressAcute Xenogeneic Graft-versus-host DiseaseMediated by Human T CellsMichael Lyman,1 Chris Lynn,1 Rachel Murray,1 OlgaTurovkaya,2 Enrique Rodriguez,1 Amy Coddington,1 IsaoSerizawa,3 Toshiyuki Tanaka,4 Shinichiro Kato,1 RachelSoloff,1 Steve Granger.1 1Kirin Pharma USA, La Jolla, CA;2La Jolla Institute for Allergy and Immunology, La Jolla, CA;3Kirin Pharma, Co., Ltd., Tokyo, Japan; 4Hyogo University ofHealth Sciences, Kobe, Japan

LIGHT is a ligand of the TNF superfamily (TNFSF14) thatpotentiates T cell mediated immune responses and exhibitspro-inflammatory activity. Like other pro-inflammatory TNFsuperfamily counterparts, aberrant LIGHT signaling has beenlinked to chronic inflammatory and autoimmune pathology insuch diseases as rheumatoid arthritis (RA) and inflammatorybowel disease (IBD). Recent reports also indicate that LIGHTmay play a role in atherosclerosis by regulating plasmalipoprotein concentrations by signaling through the lympho-toxin beta receptor (LTβR) and in graft versus host disease(GvHD) through the LIGHT-herpes virus entry mediator(HVEM) co-stimulatory pathway. We have used transchromo-somic KM mice to generate a panel of antagonistic fullyhuman monoclonal Abs (mAbs) that display high affinity forhuman LIGHT and effectively block binding of LIGHT to bothLTβR and HVEM and block LIGHT-mediated chemokinesecretion in vitro. Our anti-human LIGHT mAbs also show invivo efficacy by suppressing disease in an adoptive transfermodel of acute xenogeneic GvHD (XGvHD). Adoptive transferof human peripheral blood mononuclear cells (PBMC) intoirradiated SCID mice depleted of NK cells results in an acutelethal XGvHD mediated by CD4+ and CD8+ T cells. Prophy-lactic treatment with anti-LIGHT mAbs significantly reducesgross pathology and human Tcell numbers in recipient mice.Our data suggest that mAbs against human LIGHT may beefficacious in the treatment of inflammatory diseases of theintestines as well as in the treatment of other T-cellmediated inflammatory diseases.

doi:10.1016/j.clim.2008.03.331

Sa.111. The Human FOXP3+ Regulatory T CellPopulation: Single-cell Study Reveals a FunctionalHeterogeneity

S116 Abstracts

Eva d'Hennezel, Ciriaco Piccirillo. McGill University andMcGill University Health Center, Montreal, QC, Canada

The characterization of human naturally-occurring reg-ulatory T cells (nTREG) cells from bulk PBMC is currentlyhindered by the failure to discern nTREG cells among otherantigen-experienced CD4+ T cells in states of inflammation.The transcription factor Foxp3 has been shown to beexclusively expressed by nTREG cells in mice. In humans,the use of FOXP3 as an exclusive marker of the nTREGphenotype is not reliable, since it can also be expressed byeffector T (TEFF) cells. In order to functionally discriminatenTREG, we isolated and expanded of CD4+CD25High, CD25Neg

and CD25Low T cells at the single-cell level from PBMC ofhealthy human donors. We then correlated their FOXP3expression to their proliferative and suppressive capacityas well as to the CD25HighCD127Low phenotype and theinability to secrete effector cytokines like IFN-γ. Wefurther examined the kinetics of these phenotypes atvarious time-points after immune activation. Our single-cell analysis reveals a functional heterogeneity amongstthe FOXP3+ T cell population. Our data strongly suggeststhat FOXP3 exhibits a direct correlation with anergy.Furthermore, while cells bearing the nTREG phenotypenearly all express FOXP3, we identify a population of non-regulatory FOXP3+ T cells present in all three subsets,including CD25High cells. Moreover, we provide furtherinsights into how the upregulation of FOXP3 in TEFF cellsleads to a suppressive phenotype. Finally, our resultsindicate that FOXP3 expression on its own cannot be usedas a clinical marker for monitoring of immuno-regulation inhumans.

doi:10.1016/j.clim.2008.03.332

Sa.112. Absence of Interleukin-6 Increases Severityof Chronic Autoimmune Myocarditis FollowingCoxsackievirus InfectionMaya Poffenberger, Nadine Straka, Nahida El Warry, DianneFang, Iryna Shanina, Marc Horwitz. University of BritishColumbia, Vancouver, BC, Canada

Autoimmune myocarditis is often initiated by viralinfection. The precise mechanism by which viral infectionleads to chronic autoimmune pathology is poorly understood,however it is clear that the early immune response plays acritical role. Previous results have shown that the inflam-matory cytokine interleukin (IL)-6 is integral to the devel-opment of adjuvant-induced autoimmune myocarditis. Thefunction of IL-6 during viral-mediated autoimmunity has yetto be elucidated. To address the requirement of IL-6 duringdisease induction, IL-6 deficient mice were infected withcoxsackievirus B3 (CB3). Following infection, the micelacking IL-6 developed increased chronic autoimmunedisease pathology compared to wild type controls without acorresponding change in viral numbers in the heart. Thisincrease in disease severity was accompanied by elevatedserum levels of TNF-α, MCP-1, IL-10, activated T cells andcardiac infiltrating macrophage/monocytes. Injection of

recombinant IL-6 early following infection was sufficient tolower serum MCP-1 and strongly suggests a regulatory role forIL-6. Therefore, while IL-6 plays a pathogenic role inadjuvant-induced autoimmune disease, its function follow-ing viral-induced autoimmunity is not reprised. By regulatingthe early immune response and thereby controlling theseverity of chronic disease, IL-6 directs the outcome ofchronic autoimmune myocarditis.

doi:10.1016/j.clim.2008.03.333

Sa.113. A Novel Non-MHC Linked Locus FromMouse Chromosome 17 Confers Susceptibility toViral-Mediated Chronic Autoimmune MyocarditisMaya Poffenberger, Iryna Shanina, Nahida El Warry, DianneFang, Marc Horwitz. University of British Columbia,Vancouver, BC, Canada

Dilated cardiomyopathy, a progressive stage followingautoimmune myocarditis, is the cause of 25% of heart failurein the United States. Myocarditis is often initiated by a viralinfection from enteroviruses, including coxsackievirus B3(CB3). Viral induced myocarditis is a biphasic disease that iscomprised of an acute phase and a chronic autoimmunemediated phase. The autoimmune stage of disease occurs ingenetically susceptible hosts after the viral infection hasbeen cleared. The genetic susceptibility of mouse strains toautoimmune myocarditis is thought to involve both MHC aswell as non-MHC genes. The non-MHC genes play a dominantrole in disease susceptibility, however, no susceptibilitygenes have been identified to date. Recently, a set ofchromosome substituted strains (CSS) have been developedthat contain one chromosome from an A/J mouse on anotherwise C57BL/6 background. As A/J mice are susceptibleto myocarditis, while C57BL/6 mice are not, we can quicklyand easily determine which chromosomes contain suscept-ibility genes. This model is extremely useful alternative totransgenic or knock-out models as it more closely mimics aphysiological setting. Herein, we report the identification ofa novel 16.4 cM fragment of murine chromosome 17 thatconfers susceptibility to coxsackievirus-mediated autoim-mune myocarditis. This locus was not linked to the MHCcomplex or to any other myocarditis-associated host gene.We further established the linkage of a number of additionalregions on chromosome 17 to autoimmune myocarditissusceptibility via virus, adjuvant or shared inductionmechanisms.

doi:10.1016/j.clim.2008.03.334

Sa.114. IL-10 and Granzyme B Inhibits Suppressionby Human DR+ Effector nTregsClare Baecher-Allan, Charles Ashley, David Hafler. HarvardMedical School, Boston, MA

In humans, ex vivo MHC class II expression divides thetotal nTreg population into the two functionally distinctsubsets of the rapidly suppressive and poorly proliferative

S117Abstracts