title: Innate immunity in myasthenia gravis thymus: pathogenic effects of Toll-like receptor 4 signaling on autoimmunity.
abstract: The thymus is the main site of immune sensitization to AChR in myasthenia gravis (MG). In our previous studies we demonstrated that Toll-like receptor (TLR) 4 is over-expressed in MG thymuses, suggesting its involvement in altering the thymic microenvironment and favoring autosensitization and autoimmunity maintenance processes, via an effect on local chemokine/cytokine network. Here, we investigated whether TLR4 signaling may favor abnormal cell recruitment in MG thymus via CCL17 and CCL22, two chemokines known to dictate immune cell trafficking in inflamed organs by binding CCR4. We also investigated whether TLR4 activation may contribute to immunodysregulation, via the production of Th17-related cytokines, known to alter effector T cell (Teff)/regulatory T cell (Treg) balance. We found that CCL17, CCL22 and CCR4 were expressed at higher levels in MG compared to normal thymuses. The two chemokines were mainly detected around medullary Hassall's corpuscles (HCs), co-localizing with TLR4(+) thymic epithelial cells (TECs) and CCR4(+) dendritic cells (DCs), that were present in higher number in MG thymuses compared to controls. TLR4 stimulation in MG TECs increased CCL17 and CCL22 expression and induced the production of Th17-related cytokines. Then, to study the effect of TLR4-stimulated TECs on immune cell interactions and Teff activation, we generated an in-vitro imaging model by co-culturing CD4(+) Th1/Th17 AChR-specific T cells, naïve CD4(+)CD25(+) Tregs, DCs and TECs from Lewis rats. We observed that TLR4 stimulation led to a more pronounced Teff activatory status, suggesting that TLR4 signaling in MG thymic milieu may affect cell-to-cell interactions, favoring autoreactive T-cell activation. Altogether our findings suggest a role for TLR4 signaling in driving DC recruitment in MG thymus via CCL17 and CCL22, and in generating an inflammatory response that might compromise Treg function, favoring autoreactive T-cell pathogenic responses.
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: chiara.cordiglieri@istituto-besta.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cordiglieri
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: roberta.marolda@istituto-besta.it.
authors.forename: Roberta
authors.initials: R
authors.lastname: Marolda
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: sara.franzi@istituto-besta.it.
authors.forename: Sara
authors.initials: S
authors.lastname: Franzi
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: cristina.cappelletti@istituto-besta.it.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cappelletti
authors.affiliation: Department of Pathological Anatomy, Azienda Ospedaliera Bolognini Seriate, Via Paterno 21, 24068 Seriate Bergamo, Italy. Electronic address: anatomiapat.seriate@bolognini.bg.it.
authors.forename: Carmelo
authors.initials: C
authors.lastname: Giardina
authors.affiliation: Department of Pathological Anatomy, Azienda Ospedaliera Bolognini Seriate, Via Paterno 21, 24068 Seriate Bergamo, Italy. Electronic address: teresio.motta@bolognini.bg.it.
authors.forename: Teresio
authors.initials: T
authors.lastname: Motta
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: baggi@istituto-besta.it.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Baggi
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: pbernasconi@istituto-besta.it.
authors.forename: Pia
authors.initials: P
authors.lastname: Bernasconi
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: rmantegazza@istituto-besta.it.
authors.forename: Renato
authors.initials: R
authors.lastname: Mantegazza
authors.affiliation: Neurology IV Unit, Neurological Institute 'Carlo Besta', Via Celoria 11, 20133 Milan, Italy. Electronic address: pcavalcante@istituto-besta.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Cavalcante
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D015551:Autoimmunity; D002450:Cell Communication; D002478:Cells, Cultured; D054414:Chemokine CCL17 / Q000235:genetics / Q000378:metabolism; D054422:Chemokine CCL22 / Q000235:genetics / Q000378:metabolism; D018920:Coculture Techniques; D003713:Dendritic Cells / Q000276:immunology*; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000276:immunology*; D051381:Rats; D011917:Rats, Inbred Lew; D015398:Signal Transduction; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D058504:Th17 Cells / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D055815:Young Adult
chemical_list: D054414:Chemokine CCL17; D054422:Chemokine CCL22; D051197:Toll-Like Receptor 4
keywords: Chemokines; Dendritic cells; Myasthenia gravis; Regulatory T-cells; TLR4; Thymus