Ch.9 - Hypersensitivity Flashcards
Define/differentiate between: A. Allergic B. Autoimmunity C. Alloimmunity
Allergic - Deleterious effects of hypersensitivity to environmental antigens
AGAINST ENVIRONMENT
ex) pollen, peanuts, Type I Hypersensitivity
Autoimmunity - disturbance in the immunological tolerance of self antigens to the point that the host own tissue are damaged
AGAINST SELF
ex) Type 1 Diabetes
Alloimmunity - an individual produces an immunological reaction against the tissues of another person (mother against fetus or transplant rejection)
AGAINST OTHERS
ex) Rh- mother with Rh+ fetus
Type I hypersensitivity reactions
IgE mediated through Mast Cells
Type II hypersensitivity reactions
Tissue specific reactions, IgM and IgG.
Type III hypersensitivity reactions
Immune complex reactions. IgG.
Type IV hypersensitivity reactions
Tissue specific, cell mediated reactions. Tc.
- note Hypersensitivity reactions can be immediate (anaphylaxis) or delayed (takes hours to reach max severity sever days post exposure to the antigen)
Describe objective 2 in terms of antibodies, target tissues, and cellular components involved in the immune response and be prepared to give examples of each type of hypersensitivity reaction.
Type 1 Hypersensitivity
IgE mediated
- Involved environmental antigens –> allergens
- Repeated exposure to high levels of antigen
- Triggers the production of IgE antibodies rather than IgG or IgM. (IgE is usually only for parasites)
- Fc portion of IgE binds to mast cells
- Antigen binds to FAB portion of 2 adjacent IgE antibodies bound to Mast cell
- Repeated allergen exposure causes massive MAST CELL DEGRANULATION
- Histamine binds to H1 and H2 receptors on target cells
ex)
GI - allergens are usually foods like milk, chocolate, citrus fruits, eggs, glutin, peanut butter, fish
–> vomiting, diarrhea, abdominal pain, mal absorption
Urticaria - Hives, white fluid- filled blisters
Lungs - ASTHMA, airway obstruction of large and small airways
Describe objective 2 in terms of antibodies, target tissues, and cellular components involved in the immune response and be prepared to give examples of each type of hypersensitivity reaction.
Type II Hypersensitivity
Tissue specific autoimmunity
(can be autoimmunity or allo-immunity)
–> activation of B lymphocytes to produce IgG or IgM against a SPECIFIC ANTIGEN
–> tissues or cells have MHC markers but also have specific antigens ex) platelets and RBC’s
4 tissue effects:
- Cell destruction mediated through complement activation
ex) Autoimmune Hemolytic Anemia
Alloimmune, ABP mismatch for transfusion
- Cell Destruction through Phagocytosis
ex) Rh+ baby with Rh- mother, mom’s IgG antibodies bind and cause opsonization, tag RBC’s for destruction in the spleen, slow anemia develops - Antigen-Antibody complex attracts Neutrophils
ex) if cells are endothelial cells phagocytosis can’t occur, neutrophils will release lysoenzymes into the blood
VERY SIMILAR TO TYPE III BUT ANTIGENS ARE FIXED
- Antigen Dependent Cell Mediated Cytotoxicity
ex) Activated Tc cells or NK cells once antibody is attached. Activated Fc portion of IgG.
*** Type II doesn’t destroy the target cell but causes cells to malfunction
ex) Graves Disease
Describe objective 2 in terms of antibodies, target tissues, and cellular components involved in the immune response and be prepared to give examples of each type of hypersensitivity reaction.
Type III Hypersensitivity
Formation of antigen-antibody complexes in circulation which deposit in organs and tissue —> THIS IS NOT SPECIFIC OR FIXED LIKE TYPE II
- Formation of antigen-antibody complexes formed in circulation
Antigen is soluble and released in blood - Deposition of complex in vessel wall or in any organ or tissue
- Activation of compliment, triggers chemotaxis
- Neutrophils to to phagocytize the complexes
- Neutrophils degranulate, releasing large quantities of lysozymes causing significant tissue or organ damage
ex) Lupus Erythematosus
Antibody targets: clotting proteins, platelets, RBC’s, Nucleic Acids in circulation released from damaged cells
Immune complexes reacting with Neutrophils damage: Renal Tubular Basement Membrane, Brain Choroid Plexus, Heart, Spleen, Lung, GI tract
Anaphylactic reactions to exogenous Gamma Globulin
Describe objective 2 in terms of antibodies, target tissues, and cellular components involved in the immune response and be prepared to give examples of each type of hypersensitivity reaction.
Type IV
Tc or lymphokine producing cells (Td), activate the macrophages
***Td cells induce macrophage function
DOESN’T INVOLVE ANTIBODIES
ex) Alloimmunity - Graft Rejection
Autoimmunity - tumor rejection, hashimotos disease, DMI
Contact dermatitis –> poison oak or ivy
*** note: rarely do hypersensitivity reactions just involve one
ex) DMI B cells are destroyed by Tc cells, but low levels of anti B cells antibodies are present in blood
Describe the role of Mast cells in the type I hypersensitivity response. Identify the locations where the majority of mast cells reside. Discuss the role of Histamine, Leukotrienes, and Prostaglandin E in type I hypersensitivity reactions
Mast cells degranulate by Fc portion of IgE antibodies binding to Mast cells.
Mast cells reside tissues found in GI tract, the skin, and respiratory tract
Histamine binds to the H1 and H2 receptors on target cells.
–> causes large vessel vasoconstriction, post capillary venule dilation, increased capillary permeability, and exudation.
Leukotrienes cause smooth mm. relaxation, increased capillary permeability, vasodilation and some chemotaxic properties
Prostaglandin E cause pain and increased capillary permeability only with some chemotaxic properties
What is the role of the two different types of histamine receptors. H1 and H2
H1 receptor:
a. contraction of bronchial smooth mm.
b. increased capillary permeability –> edema
c. vasodilation exacerbating edema in throat and lungs
d. chemotaxis for eosinophils, then deactivates diapedesis so they can’t leave the inflammatory site
H2 receptor:
a. increase gastric secretion
b. decreased mast cell and basophil release of histamine
c. negative feedback loop control
Discuss briefly the value of allergy testing and the use of the flare wheel in diagnosing allergies.
Some people genetically produce more IgE antibodies, making them more susceptible to allergic reactions. Could possibly be from a diminished ability to suppress IgE secreting B lymphocytes.
1 parent with allergies –> 40% chance of allergies in offspring
2 parents with allergies –> 80% chance of getting allergies
Intradermal skin tests with small amounts of allergens. Wheel flare reactions occur in a few minutes. Diameter of wheel indicates degree of sensitivity.
In true auto-immunity, the body’s immune system attacks a tissue that normally should be
recognized as self. Explain the type of hypersensitivity each of the following is and how the hypersensitivity damages the tissues.
Hashimoto’s Disease
Hashimoto’s disease is a Type IV Hypersensitivity
Hashimoto’s disease is a result of Tc cell destruction of the thyroid gland –> leading to hypothyroidism (unexplained weight gain and fatigue)
In true auto-immunity, the body’s immune system attacks a tissue that normally should be
recognized as self. Explain the type of hypersensitivity each of the following is and how the hypersensitivity damages the tissues.
Graves Disease
Graves Disease is a Type II Hypersensitivity
IgG antibody irreversibly bind to TSH receptor and causes increased levels of thyroxine
There is no negative feed back loop for antibodies so production doesn’t end.
Person develops Graves with weight loss, puffy eyes, and enlarged thyroid.
In true auto-immunity, the body’s immune system attacks a tissue that normally should be
recognized as self. Explain the type of hypersensitivity each of the following is and how the hypersensitivity damages the tissues.
Myasthenia Gravis - weakened and rapid fatigue of mm.
This is a Type II Hypersensitivity Reaction
IgG antibody binds to nicotinic receptors on skeletal mm. and breakdown communication between mm. and nerves.
–> leads to weakness in arm and leg mm., double vision, and difficulties with speech and chewing, droopy eyelid
