Basic Immunology as it Relates to Allergy David Sloane, MD Allergy and Immunology Brigham and Women’s Hospital NESA 5 April, 2013

Disclosures (Genentech + Novartis) Unbranded Educational Talks on Asthma Contributor to the Mathematics Consortium Working Group

Objectives 1) To review the biology of cells, antibodies, and mediator molecules in healthy immunity and dys- immunity germane to allergy. 2) To explore the rationale for therapeutic agents such as omalizumab in the treatment of allergic diseases 3) Participants will develop the skills needed to educate patients about those aspects of the immune system relevant to the patient's allergic or immunologic disease and its treatment

Teleology Two theories of the purpose of the immune system: – (1) Defense against microbes (Janeway) – (2) Defense against danger (Matzinger) What do you think the difference is between these two theories?

Immune System as a Matter Processing Network InsideOutside Safe Dangerous

Reality Check

The Whole Megilah: Allergic Reaction System Slide courtesy of Dr. Tse Wen Chang

Components of the System Cells: – Dendritic Cells and other “professional APCs” – T cells – B cells – Mast cells (and Basophils?) – Eosinophils Antibodies: What are they? What are they good for? – IgE – IgG4 Mediator Molecules: What are they? What are they good for? – Interleukin (IL)-4 – IL-13 – Thymic Stromal Lymphopoetin (TSLP)

Processing Stuff Microbe Antigen Presenting Cell (APC) {DC}

Processing Stuff APC T cell

The Whole Megilah: A closer view IL4, TSLP

Wait a Minute! Why is this happening? Do the two theories of the purpose of the immune system help you? What is the hygiene hypothesis?

Antibodies: The Immune System’s Attacks Dogs From Janeway et al. Immunobiology V

Antibodies: The Various Species or Isotypes From Janeway et al. Immunobiology V

The Role of IgE in Allergic Inflammation Necessary but not sufficient factor for * antigenic * stimulation of mast cells and basophils. Prausnitz (grass) and Küstner (fish) 1920s. Reagin identified as IgE in mid 1960s.

IgE: Structure Molecular Weight ≈ 190,000 kD Monomeric, two identical heavy chains, two identical light chains (  or )

IgE: Synthesis B cells that undergo the isotype switch to C  produce IgE Help from T h 2 cells that express – a) CD40L and – b) IL-4, IL-13, TSLP

IgE: Circulation IgE circulates in the blood with a t ½ = 2-4 days (serum!) Normal serum concentration = mg/mL (the lowest of all five isotypes) x IU = 2.4x ng/mL (E.g., 125 IU = 300ng/mL)

IgE in Blood and Tissues In the blood, IgE binds to Basophils through the high affinity receptor for IgE, Fc  RI. IgE crosses from blood space into the extracellular space It binds to Mast Cells through Fc  RI Fc  RI is also expressed by monocytes, eosinophils, dendritic cells in peripheral blood, and Langerhans’ cells in skin.

Fc  RI and Fc  RII Fc  RI Structure: – One  chain that binds the Fc portion of IgE – One  chain with ITAM – Two  chains, each with ITAM Fc  RII – CD23 – Expressed on mature B cells, activated T cells, macrophages, eosinophils, follicular dendritic cells, platelets – C-type lectin – Antigen capture leading to processing and presentation to enhance immune responses.

Mast Cells (and Basophils) IgE Fc  RI

Mast Cells Live in – mucosal layers (gut, lung) – submucosal layer – dermis Mediators – Preformed (histamine, tryptase) – Rapidly synthesized (PGD2, LTC 4 ) – Not so rapidly synthesized (cytokines)

Measurement of Total Serum IgE: Why bother? Burrows B, Martinez FD, Halonen M, Barbee RA, and Cline MG. Association of Asthma with Serum IgE Levels and Skin-Test Reactivity to Allergens. NEJM 1989;320(5):

Mast Cells and IgE IgE Fc  RI Allergen Mediator Release Mast cell granules

Wait a Minute! Where is IgE acting? Where do we measure IgE?

So What?

How do we treat Allergic Inflammation? Avoid the allergenic trigger (“I can’t eat that”) Antagonize the mast cell mediators (“Where’s my antihistamine?” Throw a monkey wrench into the response system (The story of the yetzer ha’rah) Try to teach the immune network not to attack (“Stay….staaaaay…. Good dog!”)

The binding specificities of a therapeutic anti-IgE Slide courtesy of Dr. Tse Wen Chang

3 IgE:3 anti-IgE the largest Soluble and no immune complex problems Could IgE:anti-IgE complexes be beneficial? They may serve as antigen sweepers, blocking antigens to access receptors on inflammatory cells. IgE:anti-IgE complexes T 1/2 : anti-IgE ca. 20 days, IgE 1-2 days, IgE:anti-IgE ca. 20 days Immune complexes accumulate rapidly. Slide courtesy of Dr. Tse Wen Chang

Fc  RI density on basophils falls by 97% in 3 months.Fc  RI density on basophils falls by 97% in 3 months. Fc  RI on basophils decreases with a half life of about 3 days.Fc  RI on basophils decreases with a half life of about 3 days. Fc  RI on dendritic cells are decreased substantially in two weeks.Fc  RI on dendritic cells are decreased substantially in two weeks. From MacGlashan DW et al., J. Immunol. 158:1438 (1997) Down regulation of Fc  RI in patients Slide courtesy of Dr. Tse Wen Chang

Down regulation of Fc  RI in patients (cont.) From MacGlashan DW et al., J. Immunol. 158:1438 (1997)

Allergy Immunotherapy: teaching an old dog a new trick, or teaching it not to do an old trick Introduce allergen in a non-threatening manner and context Elicit an IL-10 response from T reg cells instead of an IL-4 and TSLP response from Th2 cells. Thus, lead B cells to make the isotype switch to IgG 4. IgG 4 binds to mast cell inhibitory receptors and blocks activation.

Mast Cells post Immunotherapy IgE Fc  RI Allergen NO Mediator Release Mast cell granules IgG 4 Fc  RIIb

Question 1 Which of the following cells is thought to be the primary effector cell in anaphylaxis? – A. Eosinophils – B. Basophils – C. CD8+ T cells – D. Mast cells – E. Th17 cells

Question 1 Which of the following cells is thought to be the primary effector cell in anaphylaxis? – A. Eosinophils – B. Basophils – C. CD8+ T cells – D. Mast cells – E. Th17 cells

Question 2 Which of the following cells promotes B cells to undergo an isotype switch to make IgE? – A. Th1 cells – B. Th2 cells – C. Th17 cells – D. Treg cells – E. NKT cells

Question 2 Which of the following cells promotes B cells to undergo an isotype switch to make IgE? – A. Th1 cells – B. Th2 cells – C. Th17 cells – D. Treg cells – E. NKT cells

Question 3 Fill in the blanks to make this statement correct: A major hypothesis on how allergy immunotherapy works is the belief that ____ promotes B cells to make ____. – A. IL IgE – B. IL IgA – C. IL IgG4 – D. IL IgD – E. Fractalkine.... Thymic Stromal Lymphopoetin (TSLP)

Question 3 Fill in the blanks to make this statement correct: A major hypothesis on how allergy immunotherapy works is the belief that ____ promotes B cells to make ____. – A. IL IgE – B. IL IgA – C. IL IgG4 – D. IL IgD – E. Fractalkine.... Thymic Stromal Lymphopoetin (TSLP)