title: Suppression of allergic immune responses to house dust mite (HDM) in rats exposed to 2,3,7,8-TCDD.
abstract: Exposure to various xenobiotics, including oxidant gases, diesel exhaust, and certain pesticides, has been reported to exacerbate pulmonary allergic hypersensitivity responses. Increased lymphocyte proliferative responses to parasite antigens or increased antibody responses to sheep erythrocyte have also been reported in rats exposed to TCDD before infection or immunization. As a result, these studies were conducted to test the hypothesis that TCDD exposure exacerbates the allergic response to house dust mite antigen. Brown Norway rats were injected, ip, with 0, 1, 10, or 30 microg TCDD/kg 7 days before intratracheal (it) sensitization to semipurified house dust mite allergen (HDM). Fourteen days later, rats were challenged with HDM and immediate bronchospasm was measured. At this time point, plus 2 and 7 days later, inflammatory cells in bronchoalveolar lavage fluid (BALF), HDM-specific IgE levels in serum, and HDM-driven cell proliferation in bronchial lymph nodes and spleen were evaluated. TCDD exposure decreased both immediate bronchoconstriction and specific IgE synthesis after the HDM challenge; 7 days later, HDM-specific IgE responses remained suppressed. Total serum IgE levels were similar in all groups. HDM challenge alone significantly increased cellular and biochemical indicators of lung injury, both of which were suppressed by TCDD exposure. The proliferative response of lymph node cells, but not of spleen cells, to HDM was also suppressed at the highest TCDD dose, although the splenic response to Concanavalin A was elevated. It appears that early events in the response to HDM are affected by TCDD exposure, since message for IL5 was dramatically reduced 2 days after sensitization, but not after challenge. We therefore conclude that TCDD exposure suppressed, rather than enhanced the development of allergic immune responses and the expression of immune-mediated lung disease.
authors.affiliation: Experimental Toxicology Division, NHEERL, ORD, U.S. EPA, Research Triangle Park, North Carolina, USA. luebke.robert@epa.gov
authors.forename: R W
authors.initials: RW
authors.lastname: Luebke
authors.forename: C B
authors.initials: CB
authors.lastname: Copeland
authors.forename: M
authors.initials: M
authors.lastname: Daniels
authors.forename: A L
authors.initials: AL
authors.lastname: Lambert
authors.forename: M I
authors.initials: MI
authors.lastname: Gilmour
mesh_terms: D000485:Allergens / Q000008:administration & dosage*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D016084:Bronchoconstriction / Q000276:immunology; D003208:Concanavalin A / Q000494:pharmacology; D004391:Dust / Q000009:adverse effects*; D005260:Female; D016867:Immunocompromised Host / Q000276:immunology*; D007073:Immunoglobulin E / Q000096:biosynthesis / Q000235:genetics; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000235:genetics; D007442:Intubation, Intratracheal; D008198:Lymph Nodes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D008925:Mites / Q000276:immunology*; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011914:Rats, Inbred BN; D012130:Respiratory Hypersensitivity / Q000209:etiology* / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000276:immunology
chemical_list: D000485:Allergens; D004391:Dust; D007074:Immunoglobulin G; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D003208:Concanavalin A; D007073:Immunoglobulin E