title: β2-microglobulin is required for the full expression of xenobiotic-induced systemic autoimmunity.
abstract: Mercury exposure in both humans and mice is associated with features of systemic autoimmunity. Murine HgCl₂-induced autoimmunity (mHgIA) requires MHC Class II, CD4⁺ T-cells, co-stimulatory molecules, and interferon-γ (IFN-γ), similar to spontaneous models of systemic lupus erythematosus (SLE). β₂-microglobulin (B2m) is required for functional MHC Class I molecules and the neonatal F(c) receptor (F(c)Rn). Deficiency of B2m in lupus-prone strains is consistently associated with reduced IgG levels, but with variable effects on other manifestations. Herein, we examined the role of B2m in mHgIA and show that in the absence of B2m, mercury-exposed mice failed to exhibit hypergammaglobulinemia, had reduced anti-nucleolar autoantibodies (ANoA), and had a lower incidence of immune complex deposits in splenic blood vessels, whereas IgG anti-chromatin autoantibodies and renal immune deposits were largely unaffected. Subclass analysis of the IgG anti-chromatin, however, revealed a significant reduction in the IgG₁ subtype. Examination of IFNγ, IL-4, and IL-2 in exposed skin, draining lymph nodes, and spleen following mercury exposure showed reduced IL-4 in the spleen and skin in B2m-deficient mice, consistent with the lower IgG₁ anti-chromatin levels, and reduced IFNγ expression in the skin. These findings demonstrate how a single genetic alteration can partially but significantly modify the clinical manifestations of systemic autoimmunity induced by exposure to xenobiotics.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA. mpollard@scripps.edu
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Pollard
authors.forename: Per
authors.initials: P
authors.lastname: Hultman
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Toomey
authors.forename: David M
authors.initials: DM
authors.lastname: Cauvi
authors.forename: Dwight H
authors.initials: DH
authors.lastname: Kono
authors.forename: Dwight H
authors.initials: DH
authors.lastname: Konoc
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000097:blood / Q000276:immunology; D001327:Autoimmune Diseases / Q000139:chemically induced* / Q000276:immunology / Q000473:pathology; D015551:Autoimmunity / Q000187:drug effects* / Q000276:immunology; D002843:Chromatin / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007136:Immunoglobulins / Q000097:blood / Q000276:immunology; D007668:Kidney / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D008627:Mercuric Chloride / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D060888:Real-Time Polymerase Chain Reaction; D012867:Skin / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D013154:Spleen / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D015262:Xenobiotics / Q000633:toxicity*; D001613:beta 2-Microglobulin / Q000235:genetics / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D002843:Chromatin; D016207:Cytokines; D007136:Immunoglobulins; D015262:Xenobiotics; D001613:beta 2-Microglobulin; D008627:Mercuric Chloride