MyD88 signaling. In their absence, switching of autoreactiveB-cells to the IgG2a and 2b subclasses are blocked, resultingin reduced pathology and mortality. In contrast, switching ofanti-self B-cells to IgG1 is not perturbed and generation ofnon-autoreactive IgG2a and 2b antibodies is not impaired inTLR9 deficient mice. Thus, the TLR9 pathway is a potentialtarget for therapeutic intervention in SLE.

doi:10.1016/j.clim.2006.04.214

OR.59. Impact of the Lupus Susceptibility Locus,SLE1/SLE1B On B-Cell Tolerance.Kirthi Kumar Mei Yan Chandra Mohan. UT SouthwesternMedical center, Dallas, TX.

Purpose: B6 mice congenic for the NZM2410/NZWallele ofSle1/Sle1b lupus susceptibility locus develop high titres ofANAs. These studies were designed to understand how Sle1/Sle1b might breach B-cell tolerance. Methods: B6.Sle1 andB6.Sle1b mice were bred to HEL-Ig/shEL transgenic mice andexamined for breach in B-cell tolerance. Results: We havepreviously shown that Sle1 impedes clonal anergy as seen byincreased number of HEL+ B-cells, decreased IgMb usage,increase in anti-HEL abs and increased response of B-cells toanti-IgM and sHEL in B6.Sle1.HEL-Ig.sHEL mice compared toB6.HEL-Ig.sHEL mice. Young B6.Sle1.HEL-Ig mice had in-crease in splenic T1 transitional B-cells (B220+AA4.1+CD21-CD23-) compared to B6.HEL-Ig mice (B6.HEL-Ig, 2.1 F 0.3 �106 vs B6.Sle1.HEL-Ig, 3.5F 0.4� 106, p = 0.007, n = 6, aged6—10 wks). IL-7 cultured immature B-cells from B6.Sle1.HEL-Ig mice had higher stimulation index and lower calcium flux(11.7 F 4.8% reduction, n = 6, p b 0.05) upon BCR ligationcompared to B6.HEL-Ig controls. The Sle1b sub-locusaccounted for these Sle1 phenotypes since B6.Sle1b.HEL-Igmice had expanded splenic T1 cells (B6.HEL-Ig, 2.1 F 0.3 �106 vs B6.Sle1b.HEL-Ig, 4.6 F 0.6 � 106, p = 0.001, n = 3—6,6—10 wks old), with similar calcium flux and apoptosisdefects in response to BCR crosslinking (stimulation indexwith anti-IgM F(ab)2: B6.HEL-Ig , 0.8F 0.03 vs B6.Sle1b.HEL-Ig 1.8 F 0.17, n = 3 mice, p = 0.004). Ongoing studies alsoindicate that these phenotypic differences may arise frompolymorphic variants of SLAM molecules, which have beenidentified to be candidate genes for Sle1b. Conclusions: TheSle1/Sle1b locus impairs not only clonal anergy in theperiphery but also interferes with effective toleranceinduction at the immature B-cell stage by impairing apopto-sis. The molecular mechanisms through which polymorph-isms in SLAM influence early B-cell tolerance are beingexamined.

doi:10.1016/j.clim.2006.04.215

OR.60. Mature Dendritic Cells (DCs) InduceAutoantibodies to Chromatin in Non-AutoimmuneMice That Are Characteristic of Lupus in Humansand Autoimmune Mice.John Hardin, Zhijie Zhou, Liping Xie, Diana Martins,Matthew Green. Medicine, Albert Einstein College ofMedicine, Bronx, NY.

A current hypothesis is that accentuated maturation ofDCs perpetuates lupus. We have sought to test this hypothesiswith an analysis of how DCs induce antibodies to chromatinincluding the 6 histone H1 variants (histones H1d-e and H1(0).Methods: DCs were prepared with bone marrow stem cellsgrown in culture with GM-CSF and transferred into recipientmice of the corresponding strain at two week intervals.Antibodies were assessed in immunoblot and ELISA assays.Results: Wild type DCs from C57Bl/6 mice transferred into 2month old recipients induced antibodies to histones and DNAafter 8 weeks (4 transfers). Initial antibodies were directedagainst H1d and H1e, then to H1c and H1(0), and finallyagainst core histones and DNA. This same pattern wasreproduced more rapidly when DCs from wild type Bl/6 micewere transferred into Bl/6 mice deficient in histone H1(0) orDCs fromNZB/Wmicewere transferred into 2month old NZB/W mice recipients (which also developed severe renaldisease). In contrast, untreated NZB/W mice developedanti-chromatin antibodies in exactly the same pattern butonly after the age of 5.5 months. Finally a survey of patientswith lupus indicated that almost all patients with active lupushave anti-histone antibodies (H1d and H1e N H1c and H1(0) Ncore histones). Thus the incidence of antibodies to individualhistones in lupus corresponds exactly to the pattern in whichanti-histone antibodies evolve in the mouse models. Conclu-sion: These observations demonstrate that chronic exposureto mature DCs induces an anti-chromatin response thatreplicates this response in autoimmune mice and in humanswith lupus. Thus the present study supports the hypothesisthat excessive stimulation of DCs is a factor in perpetuatinglupus.

doi:10.1016/j.clim.2006.04.216

OR.61. Abnormal B-Cell Cytokine Response in MSPoints to Distinct Roles for Naive and MemoryHuman B-Cells in Immune Regulation.Amit Bar-Or, Masaaki Niino, Martin Duddy, Caroline Bodner.Neurology and Neurosurgery, Montreal NeurologicalInstitute, McGill University, Montreal, QC, Canada.

Background: Little is known about how B-cell effectorcytokines may contribute to human autoimmune disease, andtheir potential role in regulating normal immune responses isessentially unexplored. Methods: a recently established assaymeasuring ex vivo human B-cell cytokine responses wasapplied to normals and patients with MS. Distinct therapeuticcontexts were used to probe the biology of the B-cell cytokinenetwork. Results: MS patient B-cells produced significantlyless of the downregulatory cytokine IL-10 (n = 22, p = 0.0002)while proliferation and production of the pro-inflammatorycytokines LT and TNFa were normal. In vivo mitoxantronetherapy enhanced B-cell IL-10 (n = 12, p = 0.004) yetdiminished LT (p = 0.026) and TNFa (0.006), while decreasingthe proportion of circulating CD27+ memory B-cells. Prospec-tive tracking of B-cells reconstituting following global chemo-ablation or selective B-cell depletion with rituximab, showedthat newly emerging naive (CD27�) B-cells produced most ofthe IL-10, while memory (CD27+) B-cells accounted for themajority of LTand TNFa. This profile was confirmed in freshly

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