Immunotoxicology 免疫毒理学

1. Immunotoxicology免疫毒理学 苏州大学放射医学与公共卫生学院 卫生毒理学教研室 李建祥

2. Objectives • Biology of the immune response • Types of immune responses and disorders • Tests for quantifying immunity • Testing immunotoxicity in animal models • Some specific chemicals

3. Importance of immune system • Protect against potentially harmful environmental agents

4. Biology of the immune response Innate v acquired immunity

5. Immune biology - 2 • Innate immunity • Non specific • Barriers + pro-inflammatory mechanisms • Includes • Complement • NK cells • Mucosal barriers • Phagocytic cells

6. Immune biology - 3 • Acquired immunity • Specific • Requires period of prior exposure • Increases in magnitude with continuing exposure • Variable

7. Immune biology - 4 • Lymphocytes • B cells/plasma cells – humoral • T cells – cell mediated • others • Antigen presenting cells • Play an important role in processing antigen allowing recognition - NB for T cells.

8. Immune biology - 5 • Humoral immunity • Antigens, haptens, and epitopes • B lymphocyte stimulated by foreign antigen – section recognised is epitope - enhanced by macrophage but will occur alone • Proliferation + transformation to plasma cells – germinal centres in lymphoid tissue • Production of specific circulating antibodies

9. Antigen: antibody interaction

10. Immune biology - 7 • Classes of antibody • IgG – largest proportion – subclasses – may be cytophilic rather than circulating • IgM – pentamer – initial response • IgA – dimer – j chain – secretory piece – prevent binding • IgE – parasites – allergy - eosinophils • IgD – B lymphocytes – antigen recognition

11. Classes of antibody

12. Immune biology 9 • Function of antibodies • Agglutination - neutralisation • Opsonisation – stimulating phagocytosis • Complement binding • Interaction with cell mediated immunity • Role of cytophilic antibodies • Cell activiation

13. Complement activation

14. Immune biology - 11 • Cell mediated immunity • T lymphocytes • T4 ‘helper’ cells • B lymphocyte and macrophage regulation • Th1 and Th2 forms (Th2 IL4 and IL5) • Recognise antigen associated with MHC II molecules • T8 ‘suppressor’/‘cytotoxic’ cells • Recognise and lyse virus infected cells • Recognise antigen associated with MHC I molecules

17. Immune biology - 14 • Other lymphocyte like cells • K cells • Lymphocyte morphology • antibody dependent cytotoxicity • NK cells • Targeting mechanism unclear • non antibody dependent

18. Important sites in immune function

19. Immune biology - 16 • Immune system is Complex and poorly understood • Cytokine v lymphokine v monokine v chemokine • Cyclo-oxygenase, lipo-oxygenase • Interleukins, leukotrienes, prostinoids • Free radicals, reactive oxygen species

20. Types of allergic responses • Type I • IgE mediated immediate hypersensitivity – minutes • Mast cells degranulate – histamine, serotonin - anaphylaxis • Type II • Ab mediated cytotoxicity • Type III • Soluble immune complex + complement • ‘Serum sickness’– kidneys, joints, endothelium • Type IV • Cell mediated – delayed – peak 24-48 hours • Contact dermatitis

21. Immunosupression • Loss of normal protective function • Oppertunistic infection • ? Cancers • Drugs • Other xenobiotics

22. Immune tolerance • Recognition of self • Mechanism poorly understood • Mother tolerates foetal antigens • Diseases linked to loss of self-tolerance

23. Tests for quantifying immunity • CBC + differential • Quantifying specific antibodies • Skin tests – prick and patch • Infective v allergic • Immunoglobulin concentrations • Complement components • CD4+/8+ counts • Cutaneous anergy • In-vitro tests – mitogens • Anti nuclear antibody – patterns

26. Animal models • Tier 1 • CBC + differential • Body and organ weight – e.g. – spleen, thymus. • Histology of lymphoid organs • Mitogen response • Non-specific immunity via NK function • Tier 2 • If concerns following tier 1 tests • Others • Sensitisation – guinea pig • Cell culture

27. Some specific chemicals - 1 • Respiratory • Asthmagens • Hypersensitivity pneumonitis • Mineral dusts • LPS/endotoxin • Beryllium

28. Some specific chemicals - 2 • Skin sensitisation • Contact dermatitis • Metals • Topical products – antibiotics, preservatives, antiseptics • Plants and trees • Glues/resins • Rubber constituents • Miscellaneous

29. Halogenated Aromatic Hydrocarbons - 1 • Polychlorinated biphenyls • Widely used • dielectrics, heat exchangers, printing inks, pesticide extenders • Highly lipid soluble • Accumulate in food chain • Contaminant

30. Polychlorinated biphenyls - 2 • Two major poisoning episodes • Japan 1968 - >1600 –yusho • Taiwan 1979 - >2000 –yu-cheng • Evidence of immunosupression • Decreased IgA and IgM • Skin infections, bronchitic symptoms • Decreased T cells - impaired cell mediated immunity - s/c streptokinase and streptodornase

31. Polychlorinated biphenyls - 3 • Michigan farmers – contaminated dairy products. • Increased IgG and IgA • Decreased T lymphocytes

32. Polychlorinated biphenyls - 4 • Animals • Atrophy of thymic cortex • Persistent suppression of cell mediated and humoral immunity • Reduction in germinal centres • Reduction in circulating leucocytes and lymphocytes • Increased susceptibility to infection

33. 2,3,7,8 tetrachlorodibenzodioxin (TCDD/PCDD) • Contaminant • Herbicide production • PCB production • Pulp and paper plants • Similar to PCBs • Thymic atrophy • Affect maturation of lymphocytes • Polymorphonuclear leukocytes affected

34. PCDD • Seveso – explosion at plant • No clear loss of immune function • Chloracne • Increased complement • Increase circulating T and B lymphocytes • Times beach, Missouri – dust suppression spray contaminated with TCDD • Increased mitogen responses

35. Halogenated aromatic hydrocarbons • Often occur as mixtures or contain contaminants • Precise toxic agent unclear • Age at exposure may be important • Humoral and cell mediated immunity + innate immunity

36. Pesticides - 1 • Organophosphates • Malathion – humoral • Parathion – cell mediated and humoral • Organochlorines • Chlordane – mice in utero – humoral + macrophage function • DDT – thymic atrophy, decreased mast cells • Organotins – thymic atrophy – splenic acellularity • Carbamates – suppressed PMN phagocytosis

37. Metals • Lead – increased susceptibility to E coli, L monocytogenes, mechanism unclear - ?macrophage processing • Arsenic – enhanced immune responses – complicated by chemotherapeutic effect • Mercury – activates B cells, increases IgE, induces type III hypersensitivity • Cadmium – increased susceptibility to bacterial and viral pathogens – mechanism unclear • Silica – increased risk of TB with silicosis

38. Solvents - 1 • Benzene • Myelotoxic • Toxic metabolites • - epoxide - quinones • Anaemia, leucopoenia,thrombocytopenia • Altered cell mediated and humoral immunity • Subtle effects on immunoglobulins and complement • Acute myeloid leukaemia

39. Solvents - 2 • Toluene + nitrotoluenes – decrease response to L monocytogenes • Carbon tetrachloride – decreased T cell dependent antibody response

40. Miscellaneous • 1981 - Northern Spain – contaminated cooking oil - aniline • Fever, dyspnoea, cough, exanthemata, • Eosinophilia, and increased IgE • +ve ANA, decreased lymphocytes • Vinyl chloride monomer • Systemic sclerosis like illness with +ve ANA • Alkylating agents – AML/MDS

41. MCS/IEI - 1 • Predominantly subjective complaints • Fatigue, headache, nausea, irritability • Commoner in females • Commoner in those with psychological illness • Usually triggered by odour, sometimes foods • Nonspecific triggers • Diagnosis on history + exclusion

42. MCS/IEI - 2 • No obvious immunological abnormality • Symptoms don’t resemble known immunologically mediated diseases • No objective evidence of inflammatory response • Probably multifactorial • Treatment options unclear

43. Summary • Competent immune system essential • Immune function complex and not well understood. Integrated mechanism • Disease may occur due to • Hypersensitivity • Immunosuppression • Autoimmunity • Tests of immune function not comprehensive

44. 第一节: 概述 • 定义： 免疫毒理学（immunotoxicology）主要研究外源化学物和物理因素等对机体免疫系统的损害作用、生物学机制及其危险度评价与管理。是在免疫学和毒理学基础上发展起来的一门毒理学分支学科。

45. 它主要研究外来化合物和物理因素对人和实验动物免疫系统产生的不良影响及其机理。它主要研究外来化合物和物理因素对人和实验动物免疫系统产生的不良影响及其机理。 • 很多外来化合物、各种化疗药物及物理因素都会引起免疫功能产生一定的变化，而且这种变化往往在其它毒性症状之前发生。因此研究外来化合物对免疫功能的影响，一方面可对它们的毒性作出全面的评价，另外还可从免疫功能的检查中寻求外来化合物对机体损伤的早期检测指标。

46. 主要研究内容： • 1.免疫毒性及作用机制研究 • 2.免疫毒性评价的方法学研究 • 3.免疫毒性的危险度评价

47. 1.免疫毒性及作用机制研究 采用各种有效的研究手段，从整体、器官、细胞和分子等不同水平研究外源化学物和物理因素对人和实验动物的免疫损害，包括免疫抑制、超敏反应和自身免疫反应。并分析其作用机制。

48. 2.免疫毒性评价的方法学研究 • 改进、规范和完善已有的免疫毒理学试验方法，探索更灵敏、特异，更有预测价值的新方法和更全面合理的试验组合，提高试验的可靠性和效能。 • 同时，为了顺应国际发展趋势，从动物伦理学角度出发，还要研究免疫毒理学的体外替代试验方法，以减少使用实验动物的数量。

49. 3.免疫毒性的危险度评价 研究适合用于人群危险度评价的免疫毒性试验的观察终点，实验动物和人群免疫毒性的剂量反应规律和特性，建立合理的外推模型，分析免疫毒性的人群易感性和不同免疫危害的可接受危险度水平等。

50. 免疫学概述 1 免疫学的概念 2 免疫系统的构成与功能