Immunopathology: Hypersensitivity Overview

Type III hypersensitivity involves IgG antibodies, while type I involves IgE antibodies.

The Arthus reaction typically peaks at 4-8 hours.

Extrinsic allergic alveolitis is triggered by inhaled antigen complexes with specific IgG in the alveoli.

<p>Type IV hypersensitivity is initiated by antigen-specific T cells, unlike type I and III which involve antibodies.</p> Signup and view all the answers

<p>Cytokines produced by activated T cells recruit macrophages and other T cells, creating a cellular infiltrate.</p> Signup and view all the answers

<p>Hypersensitivity reactions are exaggerated or inappropriate immune responses that cause tissue damage, unlike protective immune reactions that promote healing and defense.</p> Signup and view all the answers

<p>Type I hypersensitivity reactions are mediated by IgE, which induces the activation of mast cells resulting in the release of histamines and other inflammatory mediators.</p> Signup and view all the answers

<p>Type II hypersensitivity involves IgG binding to cell-surface or matrix antigens, engaging Fc-receptor and complement-mediated effector mechanisms that can damage the cells.</p> Signup and view all the answers

<p>Type III hypersensitivity reactions are characterized by the formation of immune complexes of IgG and soluble antigens, leading to tissue damage through Fc-receptor and complement activation.</p> Signup and view all the answers

<p>In Type IV hypersensitivity, T cells mediate the immune response; TH1 cells activate macrophages for inflammation, and cytotoxic T cells directly inflict damage on tissues.</p> Signup and view all the answers

<p>Environmental factors like allergens and pollutants, along with genetic predispositions, can increase the risk of developing hypersensitivity by influencing immune system responses.</p> Signup and view all the answers

<p>Therapeutic strategies for hypersensitivity reactions include avoidance of triggers, use of antihistamines, corticosteroids, and immunotherapy to desensitize patients.</p> Signup and view all the answers

<p>The three groups include damage from TH1 cell activation leading to macrophage inflammation, TH2 cell-induced eosinophil responses, and direct cytotoxic effects from CTLs.</p> Signup and view all the answers

<p>Mast cells are activated by the cross-linking of Fc epsilonRI receptors through antigen binding to bound IgE molecules.</p> Signup and view all the answers

<p>Eotaxin is a chemokine released by eosinophils, playing a crucial role in recruiting these cells to sites of allergic inflammation in asthma.</p> Signup and view all the answers

<p>Individuals with allergic parents are more than twice as likely to develop allergies, whereas those with non-allergic parents have less than half the likelihood compared to the general population.</p> Signup and view all the answers

<p>The 'hygiene hypothesis' suggests that early exposure to infectious agents promotes a TH1 immune response, reducing the risk of developing atopic diseases.</p> Signup and view all the answers

<p>Allergic rhinitis is caused by airborne allergens reacting with IgE-sensitized mast cells in the nasal passages and conjunctiva.</p> Signup and view all the answers

<p>Systemic anaphylaxis can be triggered by ingestion of nuts or seafood, insect bites, or drug injections, leading to severe vasodilation and bronchoconstriction.</p> Signup and view all the answers

<p>Environmental factors, along with genetic susceptibility, significantly influence the development of atopic allergic diseases, with exposure levels affecting immune responses.</p> Signup and view all the answers

<p>In type I hypersensitivity, symptoms like asthma result from the release of vasoactive mediators leading to bronchoconstriction and inflammation.</p> Signup and view all the answers

<p>48-72 hours</p> Signup and view all the answers

<p>Lymphocytes and macrophages, along with edema of the epidermis.</p> Signup and view all the answers

<p>Lymphocytes, monocytes, and macrophages.</p> Signup and view all the answers

<p>Persistent antigen presence, hardening, and the formation of giant cells.</p> Signup and view all the answers

<p>21-28 days</p> Signup and view all the answers

<p>Poison ivy or heavy metals.</p> Signup and view all the answers

<p>A cell-mediated immune response.</p> Signup and view all the answers

<p>TH1 cells influence and regulate the cell-mediated immune response.</p> Signup and view all the answers

<p>The dose and route of allergen exposure.</p> Signup and view all the answers

<p>Fc dependent mechanisms and complement recruitment via the classical pathway.</p> Signup and view all the answers

<p>The loss of red blood cells due to their destruction.</p> Signup and view all the answers

<p>Hemolysis occurs due to antibodies binding to red blood cells, leading to ADCC or complement-mediated lysis.</p> Signup and view all the answers

<p>The sensitization of a Rh-negative mother to Rh-positive fetal blood.</p> Signup and view all the answers

<p>IgM and IgG antibodies.</p> Signup and view all the answers

<p>Complement-mediated lysis and antibody-dependent cellular cytotoxicity (ADCC).</p> Signup and view all the answers

<p>Outside the bloodstream, particularly in the spleen, liver, and bone marrow.</p> Signup and view all the answers

<p>Activated T cells produce cytokines like IL-2 and IFN-gamma, which cause macrophages to aggregate into nodules.</p> Signup and view all the answers

<p>IgE-mediated hypersensitivity reactions occur within 2-30 minutes.</p> Signup and view all the answers

<p>Antibody-mediated cytotoxic hypersensitivity involves antibodies directed against cell-surface antigens that mediate cell destruction via ADCC or complement activation.</p> Signup and view all the answers

<p>In immune complex-mediated hypersensitivity, antigen-antibody complexes deposited at various sites induce degranulation of mast cells and PMN, leading to tissue damage.</p> Signup and view all the answers

<p>Memory TH1 cells release cytokines that recruit and activate macrophages during cell-mediated hypersensitivity.</p> Signup and view all the answers

<p>Granulomas represent a sustained immune response where activated macrophages and lymphocytes aggregate to contain pathogens.</p> Signup and view all the answers

<p>The main mediator for mast cell degranulation in immune complex-mediated hypersensitivity is FcgammaRIII.</p> Signup and view all the answers

<p>Two examples of IgE-mediated hypersensitivity are hay fever and asthma.</p> Signup and view all the answers