1、MaryJane SelgradeNational Health&Environmental Effects Research Laboratory,U.S,EPA,Research Triangle Pk,NCSelgrade.MaryJaneEPA.GovSeptember 18,2006 Mechanisms of immune mediated injury Chemicals which elicit immune responses Contact sensitivity Respiratory sensitivity Food Allergy Chemicals which mo
2、dulate responses to other antigensDefinition:Excessive humoral or cellular response to an antigen which can lead to tissue damage Type 1:IgE mediated(Immediate type)Type 2:IgM,IgG,cytolysis of cells Type 3:IgM,IgG Immune complex mediated Type 4:T-cell mediated(delayed-type)(Gel&Coombs classification
3、)InductionSensitization(1st exposure)ElicitationChallenge(subsequent exposure)Example:Bee StingMediators(as such Histamine)BronchoconstrictionMast CellDegranulationAg Ab(or autoantibody)Ag binds to cell surfaceCell lysisAb bind to cell bound antigenExamples:Goodpastures syndromeHemolytic anemiaAg Ab
4、Formation ofAg/Ab complexes;Deposition in tissuesActivation of macrophagesAnd ComplementInflux of PMNs,Eosinophils,Lymphocytes(Inflammation)PolymorphonuclearleukocyteActivatedmacrophageExamples:Late onsetasthmatic response,fibrosis,serum sicknessInflammatory activityCytokinesActivatedmacrophage Anti
5、genAg presenting cellActivated T cell AntigenAg presenting cellClonal expansionExample:ContactSensitivityClass I MHC peptide generally derived from protein produced within the cell peptide generally derived from protein taken up by the cell Class II MHC cell membrane Recognised by TCR of CD4 T cells
6、 Recognised by TCR of CD8 T cells cytoplasm with bound peptide with bound peptide Antigen Presented to T Cells Via MHCIL-4 IL-10IL-5 IL-13 IL-6IL-2 TGF IFN Suppresses TH2Suppresses TH1IgG2a,CF Antibody DTH,CytotoxicityIgE,IgG2b,IgG1Mast Cells+EosinophilsDefense Against Intracellular PathogensInflamm
7、atory DiseasesDefense Against Parasitic InfectionImmediate-type HypersensitivityImmune cellTh1Th2CD8(CTL)TcantigenSoluble(MHC II)Soluble(MHC II)Cell-associatedMHC I)Effector mechanismMacrophage activationEosinophil activationcytotoxicityExamplesTuberculin RxContact dermatitisChronic asthma/allergyCo
8、ntact dermatitis Can themselves act as antigens Haptens Contact sensitizers Respiratory sensitizers Systemic hypersensitivity(drugs)Proteins Respiratory allergens Food Allergens Systemic hypersensitivity(drugs)Can enhance development or expression of allergic reactions Cosmetics and Fragrances Dyes
9、Preservatives(formaldehyde Metals(Ni,Co,Be,Cr)PesticidesIL-1B,IL-6,IL-12ALLERGENLANGERHANS CELL(LC)EDEMA AND ERYTHEMAINDUCTION PHASE ELICITATION PHASELC AND LYMPHOCYTE INTERACTION“PRIMED”LYMPHOCYTESCELLULAR INFLUXNONSPECIFIC INFLAMMATORY MEDIATORSSPECIFIC RESPONSEMigration to Local Lymph NodeLYMPHOC
10、YTE PROLIFERATION ID injection w/and without FCA plus topical application:Days 5-8Day 20-22 topical challengeRead:48,72 h after challenge30%positiveTopical application-closed patch:Days 0,6-8,and 13-15 Day 27-28 topical challengeof the untreated flank for 6 h Read:21,24,48 h after removing patch 15%
11、positiveInductionChallengeEndpoint erythemaCriteria20 animals/group Application of Agent or Vehicle to Back(local)or Abdomen(systemic)Application of Agent Measure Ears:24-48 hours post challengeSensitizationInduction PeriodChallengeAgent applied to ears Days 1,2,3IV 3H-thymidine injection Day 6isoto
12、pe incorporation scintillation counting5 hour after IV injection Proliferation measure:Endpoint expressed as dpmElicitationPHASELLNAMESTInductionGPMT and BA Computer modeling using chemical structure to predict ability to induce CHS Based on following concepts:Biologic mechanism of chemical effect i
13、s related to structure Chemicals with related structures have similar mechanisms&hence effect How do SAR&QSAR models work Chemical structure added into program Structure compared to structures in data base of know contact sensitizers Structures associated with sensitizers are flagged(llergic ontacte
14、rmatitis)102030405060708019801981-19831984-19861987-19891990-19921993-1994Rate(per thousand)0-4 yr5-1415-3435-6465Total Bronchoconstriction IgE mediated(IL-4)Hyperresponsive to non-specific stimuli(methacholine)Eosinophilic Inflammation Th2 mediated (Il-5,IL-13)Proteins-e.g detergent enzymes,biotech
15、 Haptens(low molecular wt)-isocyanates&anhydrides,platinum Adjuvants-air pollutionTemperature transmitterAgexhaustairoscillographDifferentialPressure transducerMeasures pulmonaryresponseCriteria for Positive ResponseRespiratory rate 35%Temp 0.6%Protein allergens Detergent Enzymes Molds and spores La
16、tex microbial pesticides animal dander*Not all proteins are equally allergenic;as yet no particular amino acid sequences has been associated with allergenicity IT dose response cytophilic Ab response to unknown IT dose response to Alcalase(subtilisin B)Test protein/Reference protein=relative potency
17、 Relative potency 1 adjust by appropriate factor Toluene diisocyanate Diphenylmethane diisocyanate Phthalic anhydride Trimellitic anhydride Platinum salts Reactive dyes 50 or so known allergens(asthmagens)Karol test-Inhalation exposure,respiratory effects,Guinea pig Sarlo approach-Guinea Pigs Struct
18、ure activity In vitro reactivity with protein In vivo antibody response(IT exposure)In vivo reactivity(Karol test)Mouse IgE test-exposure variation of LLNA assess total serum IgE Cytokine profiling exposure variation on LLNA assess cytokine profiles in draining lymph node,look for differences in exp
19、ression of Th1,Th2 profiles LLNA Rodent models Nitrogen dioxide(NO2)Residual oil fly ash(ROFA&Human Diesel exhaust&Rhesus Monkey OzoneIL-4 IL-10IL-5 IL-13 IL-6IL-2 TGF IFN Suppresses TH2Suppresses TH1IgG2a,CF Antibody DTH,CytotoxicityIgE,IgG2b,IgG1Mast Cells+EosinophilsDefense Against Intracellular
20、PathogensInflammatory DiseasesDefense Against Parasitic InfectionImmediate-type Hypersensitivity Nature or Dose of Antigen Local Micro Environment cytokines&other mediators produced by macrophages&epithelial cells Genetics of Host Route of Exposure Around 5%of children and 2-3%or adults have food allergies Manifestations can range from life threatening anaphylaxis,to respiratory or gut irritation Peanut classic example Toxicologist involved because of GMOs acid resistant homology with known allergens
