Over-Reactions of the Immune System

1. Over-Reactionsof theImmune System • Learning Objectives • Learn the distinguishing features of Types I, II, III & IV hypersensitivity. • Know the cells and mediators involved in each type. • Understand the basic mechanism underlying each type. • Recognize clinical scenarios characteristic of each type. • Appreciate treatment options. Larry Schwartz, MD, PhD

2. Over-Reactions of the Immune System • Hypersensitivity diseases are caused by an immune response, regardless whether the immune response is against a pathogen, non-pathogen or self. • Further, the response may be caused by antibodies and/or cells, and also may involve innate responses.

3. Allergen IgE Mast cell/basophil eosinophil Antigen IgG neutrophils Antigen TH1/CTL macrophages

4. Development of Immediate Hypersensitivity antigen antigen antigen processing Anaphylaxis Hives/Dermatitis Asthma/Rhinitis Conjunctivitis APC/DC presentation IL-4 TH0→2 help B/→e IL-4/13 trigger mediator release arm mast cells IgE production

5. Sensitization to Inhaled Pollen

6. Late 6 h Early 15 min

7. Figure 10-1 Latex ~ IgE Non-IgE, Type IV

8. ?

9. 2008 Mar 13;358(11):1109-17

10. DerP2 allergenicity results from functional mimicry of a Toll-like receptor 4 complex protein Divanovic et al. Nature457:585-588, 2009 LPS:MD2:CD14 TLR4 → LPS:DerP2:CD14 ← TLR4 (TLR4-dependent, MD2-independent) Allergic Lung Inflammation TLR4+ TLR4-

11. Susceptibility Genes for Asthma & Atopy GeneNature of PolymorphismPossible mechanism of association IL-4 promoter variant variation in IL-4 expression IL-4Ra structural variant increase signaling to IL-4 MHC II structural variant enhanced allergen peptide presentation TCR-A microsatellite markers enhanced T cell response to allergens TIM Genes promoter/structural TH1/TH2 balance FcεRIβ structural variant variation in signaling via IgE 5-lipoxygenase promoter variants enhanced leukotriene production b2-AR structural variants β2 bronchodilator intolerance ADAM33 metalloprotease altered activity TH2 Mast Cells &Mediators Target tissue response

12. Birth Th2 Older sibs Only child Many infections (Th1 stimuli) Few infections No allergies Allergies Th1 Still Th2 The Hygiene Hypothesis

13. IgE:FcεRI FcεRI Tetramer (trimer) 1010M Kdα:IgE β amplifies γ transduces FcεRI β α IgE IgE 4 Constant domains (175 kDa) <250 ng/ml (16x1010 M) (vs IgG 10 mg/ml) Circulation t½ ~ 2 days Heat-labile Fcε γ2

14. Immediate Hypersensitivity IgG-mediated Hypersensitivity Cell-mediated Hypersensitivity Biologic Fibrosis/Fibrolysis Vasopermeability Smooth muscle contractility Angiogenesis Anti-coagulation/ thrombosis Transplant Tolerance Mast Cells Venom Detoxification Immunity Bacteria Viruses Parasites

15. MCT & MCTC Cells ~ Development of Distinct Types of Human Mast Cells MCT Tryptase • MCTC • Tryptase • Chymase • Carboxypeptidase • Cathepsin G • CD88 Tissue SCF+? Mast Cell (committed) progenitor Circulation IL-5 • Eosinophil • Basophil Progenitor IL-3 SCF Bone Marrow MC (Kit+)

16. Anti-Tryptase Immunocytochemistry & Immunogold Electron Microscopy Tryptase+/Chymase- MCT Tryptase+/Chymase+ MCTC MCTC MCT ~tryptase ~chymase Skin Perivascular Bronchial smooth muscle Bowel submucosa Lung parenchyma Small bowel mucosa

17. Anti-IgE blocking Ab FceRI-Dependent/Independent Activation of Mast Cells Multivalent Antigen Anti-IgE (Fce) Anti-FceRI Univalent Ag Y Y Y Y Y Y MCT/TC Y MCTC C3a C5a CD88 Substance P Neurokinin A CGRP Morphine/Codeine Vancomycin Major Basic Protein (eosinophil)

18. Resting Mast Cell Activated Mast Cell Preformed Granule Mediators Newly-Generated Lipids, Cytokines, Chemokines

19. Figure 10-5 Preformed in granules Newly-generated & secreted

20. Histamine 1st pass; ~2 min t½ histidine decarboxylase metabolites Histidine Receptors H1: vasoactive, itch, bronchospasm, mucus H2: gastric acid, ±vasoactive H3:CNS H4:itch, leukocytes Antihistamines diphenhydramine, cetirizine, fexofenadine, hydroxyzine famotidine, ranitidine

21. Arachidonic Acid Products Aspirin NSAIDs Zileuton Montelukast Zafirlukast DP1 CRTH2 (DP2) CysLT1/2 D4 E4 vasodilate/vasopermeability bronchospasm antithrombotic vasodilate/vasopermeability bronchospasm mucus production inflammation tissue remodeling

22. Activated mast cells/basophils amplify IgE production? ↑ IL-13R (Bas) IL-13 (MC)  FcεRI →  mast cell sensitivity to low levels of allergen

23. Basophil Mediators Histamine LTC4 PAF IL-4 Anti-Basophil mAb Allergen 6h Buffer 6h

24. Basophils Play a Pivotal Role in IgG but not IgE Mediated Systemic Anaphylaxis (mouse) Tsujimura et al. Immunity 28: 1-9, 2008 IgG ICs → basophil FcγRIII → PAF Basophils Play a Critical Role in the Development of IgE-Mediated Chronic Allergic Inflammation Independently of T Cells & Mast Cells (mouse) Mukai et al. Immunity 23: 191-202, 2005 Allergen:IgE → MC → MC±Bas → Bas 15 min 4-6 h 3-5 d

25. Eosinophil Rothenberg NEJM, 1998

26. Eosinophil Mediators Figure 10-9

27. Eosinophils detected by their bright orange coloration and bi-lobar nuclei Nasal probe

28. Hypereosinophilic Syndrome (anti-IL-5)

29. Figure 10-12 Urticaria

30. Figure 10-18

31. Figure 10-19

32. Allergic rhinitis is caused by allergens entering the respiratory tract Eotaxins 1-3:CCR3

33. MCTandMCTCMast Cells in Nasal Mucosal Seasonal allergic rhinitis Normal subepithelium subepithelium epithelium lumen epithelium

34. The acute response in allergic asthma leads to TH2-mediated chronic inflammation of the airways

35. Inflammation & remodeling of airways in chronic asthma restricts airflow mucus plug thickened airway wall eosinophils basophils lymphocytes epithelial desquamation

36. Allergen-induced release of histamine by mast cells in skin causes a wheal and flare (hive, urticaria) Hive at 15 min ~ transudate (without inflammatory cells) Late phase at 4-6h ~ cellular infiltrate

37. Ingested allergens cause vomiting, diarrhea & hives(acute urticaria) vs Chronic Urticaria (anti-FcεRIα or other autoimmune pathways)

38. Systemic Anaphylaxis allergen epinephrine i.m.

39. Postage stamp issued by Monaco in 1953 to commemorate the 50th anniversary of the discovery of anaphylaxis Dworetzky et al. JACI 110:331-336, 2002.

40. Charles Richet1913 Nobel Prize for Physiology & Medicine • A subject that had a previous injection is far more sensitive than a new subject. • (2) The symptoms characteristic of the second injection, do not in any way resemble the symptoms characterizing the first injection. • A three or four week incubation period must elapse before the anaphylactic state results. • An anaphylactic state is produced by taking the blood of an anaphylactized animal and injecting it into a normal animal subject (passive)

41. Approaches to the treatment of allergy Target Specific Approach Mechanism T cells Reverse TH2 > TH1 or ↑Treg & ↓TH2 IT: Ag/peptides Cytokines CpG/ TLRs B cells → IgE Block co-stimulation Inhibit TH2 cytokines Inhibit CD40L, IL-4, IL-13, CD20 Mast cells Inhibit IgE binding to mast cells Anti-IgE Kit? Mediator action Receptor antagonists Synthesis inhibitors Antihistamines Anti-TNF CysLT1 antagonist COX1/2 inhibitors Eosinophil- dependent inflammation Block cytokine & chemokine receptors that recruit/activate eosinophils Anti-IL-5 Block CCR3 -agonist Smooth muscle/vascular

42. CASE 15 A 65 year-old accountant collapsed on the street 20 minutes after a penicillin injection had been administered in a physician's office. PMH: angina, coronary atherosclerosis. No history of allergic rhinitis, asthma or dermatitis. Received penicillin four or five times in the past for respiratory infections without adverse reaction until the last time → urticaria that resolved spontaneously. One day prior to admission ~ sore throat and fever. On the morning of admission ~ family physician, who prescribed an injection of a "penicillin" that was administered by the nurse. The patient immediately left the office with her husband and started walking home. About 10-15 minutes later, she began to feel weak and became diaphoretic. She complained of difficulty breathing and chest pain and slid to the ground. Her husband hailed a passing taxi and brought her to the emergency room in a trip lasting less than 10 minutes.

43. ER: ashen in appearance; cold, clammy skin; tachycardia (160); hypotensive (systolic BP 50); labored respiration with wheezing. Rx: epinephrine SQ, two wide-bore intravenous lines to administer fluids and diphenhydramine (benadryl). ENT exam: tracheotomy deemed not necessary. Acute laryngeal edema in a different patient who died from an anaphylactic reaction to penicillin. An emergent tracheotomy might have been lifesaving in this instance.

44. Within 20 minutes BP, P & respirations improved and over next few hours returned to normal. Additional Rx: diphenhydramine; oral prednisone. ECG (electrocardiogram) ~ new T-wave inversions ~ small MI. Uncomplicated post-MI course. On the fifth hospital day, negative allergy skin tests to penicillin. Discharged the following day.

45. Case 15 Questions (1) Was penicillin appropriate and could the allergic reaction have been predicted? (2) Should she have been allowed to leave the doctor's office so promptly? (3) Immunological events leading to this reaction? Why no reaction to initial penicillin? (4) Which therapeutic agent (Benadryl, prednisone, epinephrine, fluids) was critical in saving her life? Should prednisone have been given earlier? (5) Were any other allergic reactions apt to occur after the first day? (6) Why were skin tests negative? (7) If the patient later needed penicillin, could she receive it? (8) What is urticaria and how did it develop? (9) Penicillin also causes another type of hypersensitivity. Describe. (10) What are other possible etiologies of urticaria other than drug allergy? (11) Were there any contraindications in this patient to epinephrine?

47. Type II: Penicillin & other small-molecule drugs modify (haptenize) human cells → display foreign epitopes

48. Type II: Penicillin-protein conjugates stimulate the production of anti-penicillin Abs T:B:Ab ?C’ Ab:FcR C’:CR Hemolytic anemia APC:T cell

50. Type III: immune complexes