title: Characterization of TLR4-mediated auto-antibody production in a mouse model of histidyl-tRNA synthetase-induced myositis.
abstract: We have previously shown that intramuscular immunization with a recombinant fragment of murine histidyl-tRNA synthetase (HRS) in the absence of exogenous adjuvant generates Ag-specific, IgG class switched Abs a murine model of myositis. Markedly diminished IgG anti-HRS auto-Ab responses in TLR4 signaling-deficient C3H/HeJ mice indicate that TLR4 is required for auto-Ab formation and/or class switching in this system. Comparative time course assessment of HRS-immunized C3H/HeOuJ (wild type) and C3H/HeJ (TLR4 mutant) mice shows here that despite significant impairment of class switched IgG anti-HRS responses in TLR4-deficient C3H/HeJ mice, production of IgM anti-HRS auto-Abs is relatively preserved-suggesting that TLR4-mediated signals modulate IgG class switching rather than auto-Ab formation in this genetic background. In C57BL/6-derived knockout mice lacking either MyD88 (B6.MyD88(-/-)) or TRIF (B6.TRIF(-/-)) adaptor molecules, immunization studies indicate that TRIF exerts a dominant role in the generation of HRS-specific IgG auto-Abs. Complementing these analyses, in vitro stimulation of unfractionated, as well as T cell-depleted, C3H/HeOuJ splenocytes with recombinant murine HRS reveals that TLR4-mediated generation of class switched auto-Abs can occur independently of T cell help. Overall, these findings support a broader role for TLR4 in the breakdown of immune tolerance and development of autoimmunity.
authors.affiliation: Department of Medicine, Division of Rheumatology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Harlow
authors.forename: Irina
authors.initials: I
authors.lastname: Fernandez
authors.forename: Makoto
authors.initials: M
authors.lastname: Soejima
authors.forename: William M
authors.initials: WM
authors.lastname: Ridgway
authors.forename: Dana P
authors.initials: DP
authors.lastname: Ascherman
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics; D000818:Animals; D000917:Antibody Formation / Q000235:genetics; D001323:Autoantibodies / Q000276:immunology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D006643:Histidine-tRNA Ligase / Q000276:immunology*; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000235:genetics; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics; D020721:Nervous System Autoimmune Disease, Experimental / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D001323:Autoantibodies; D006643:Histidine-tRNA Ligase; D053594:Myeloid Differentiation Factor 88; D051197:Toll-Like Receptor 4; C476286:Ticam1 protein, mouse