title: Engagement of TLR2 reverses the suppressor function of conjunctiva CD4+CD25+ regulatory T cells and promotes herpes simplex virus epitope-specific CD4+CD25- effector T cell responses.
abstract: PURPOSE. The authors recently reported that Foxp3(+)CD4(+) CD25(+(Bright)) "natural" regulatory T cells (nT(reg) cells) are abundant in rabbit conjunctiva and suppress herpes simplex virus (HSV)-1-specific CD4(+) and CD8(+) effector T cells (T(eff) cells). However, little is known about the overall regulatory mechanisms of these nT(reg) cells. The authors investigate the regulation of conjunctiva-resident nT(reg) cells through Toll-like receptors (TLRs) and their effect on ocular mucosal T(eff) cell immunity. METHODS. CD4(+)CD25(+) nT(reg) cells were purified from naive rabbit conjunctivas, and their TLR expression profile was determined. The effects of TLR engagement on nT(reg) cell-mediated suppression of CD4(+) T(eff) cells were determined in vitro and in vivo. RESULTS. The authors found that conjunctiva-resident nT(reg) cells express high levels of TLR2 and TLR9; exposure to the TLR2 ligand lipoteichoic acid (LTA) led to the increased activation and proliferation of nT(reg) cells, and the addition of autologous APCs further increased nT(reg) cell expansion; in contrast, the TLR9 ligand CpG(2007) inhibited the proliferation of nT(reg) cells, and the addition of autologous APCs had no effect on such inhibition; nT(reg) cells treated with LTA, but not with CpG(2007), expressed IFN-γ and IL-10 mRNA, but not TGF-β; consistent with in vitro data, rabbits immunized by topical ocular drops of HSV-gD peptides + TLR2 ligand (LTA) displayed enhanced CD4(+)CD25(-) T(eff) cell immune responses when compared with HSV-gD peptides + TLR9 ligand (CpG(2007)). CONCLUSIONS. Although conjunctiva-resident CD4(+)CD25(+) nT(reg) cells express high level of TLR2 and TLR9, their suppressive function is more significantly reversed after the administration of TLR2 ligand (LTA; P < 0.005) than of TLR9 ligand (CpG(200); P > 0.005). These findings will likely help optimize the topical ocular administration of immunotherapies.
authors.affiliation: Laboratory of Cellular and Molecular Immunology, Gavin Herbert Eye Institute, School of Medicine, University of California at Irvine, California.
authors.forename: Gargi
authors.initials: G
authors.lastname: Dasgupta
authors.forename: Aziz Alami
authors.initials: AA
authors.lastname: Chentoufi
authors.forename: Sylvaine
authors.initials: S
authors.lastname: You
authors.forename: Payam
authors.initials: P
authors.lastname: Falatoonzadeh
authors.forename: Lourie Ann A
authors.initials: LA
authors.lastname: Urbano
authors.forename: Ayesha
authors.initials: A
authors.lastname: Akhtarmalik
authors.forename: Kimberly
authors.initials: K
authors.lastname: Nguyen
authors.forename: Lilit
authors.initials: L
authors.lastname: Ablabutyan
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Nesburn
authors.forename: Lbachir
authors.initials: L
authors.lastname: BenMohamed
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000276:immunology; D002478:Cells, Cultured; D003228:Conjunctiva / Q000187:drug effects / Q000276:immunology*; D016207:Cytokines / Q000235:genetics; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D005260:Female; D018259:Herpesvirus 1, Human / Q000276:immunology*; D007111:Immunity, Cellular / Q000502:physiology; D053645:Interleukin-2 Receptor alpha Subunit / Q000276:immunology; D008024:Ligands; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D013682:Teichoic Acids / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000378:metabolism*; D051217:Toll-Like Receptor 9 / Q000378:metabolism
chemical_list: D015704:CD4 Antigens; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; D053645:Interleukin-2 Receptor alpha Subunit; D008024:Ligands; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D051217:Toll-Like Receptor 9; C009900:lipoteichoic acid