Hypersensitivity Flashcards
What is a hypersensitivity reaction?
An immune reaction against self-antigens resulting in autoimmune disease.
Excessive undesirable reactions
How many classes of hypersensitivity reactions are there?
Type I-IV (1 to 4)
Which hypersensitivity reactions are associated with antibody action?
1 to 3
What are Type IV hypersensitivity reactions are associated with?
T-lymphocytes and cell-mediated responses
Which antibody activates complement?
IgG3
What does IgG3 complement also mediate?
Fc mediated phagocytosis
What does IgE antibody induce?
Mast cell degranulation
Which antibody region is complementary to the antigenic structures present on pathogens?
Variable regions
Which cells secrete antibodies?
Plasma cells
What is the term referred to as the clone of plasma cells secreting specific antibodies in response to a particular antigen?
Monoclonal antibodies
Describe the structure of an antibody:
2 heavy chains held together by disulfide bridges, connected to 2 light chains via a hinge region, considered as the antigen-binding site;
How are the two heavy chains present within antibodies held together?
Disulfide bridges
Which region of the antibody is considered to be the antigen-binding site?
The hinge region
What is a type 1 hypersensitivity reaction?
Anaphylactic/immediate hypersensitivity: Provoked allergic reaction by re-exposure to a specific antigen- allergen
What is the immune mediator for type 1 hypersensitivity reactions?
IgE
Which diseases are commonly associated with type 1 hypersensitivity reactions?
Asthma, allergic rhinitis, and atopic dermatitis
What mediator is released through IgE antibodies?
Histamine
Which cells secrete histamine in response to IgE antibodies?
Mast cells and basophils
What is the response elicited by histamine?
Vasodilation
Inflammatory response
Cell diapedesis (Increasing capillary permeability and accumulation of fluid within the interstitial space)
What is a multivalent environment antigen?
An antigen that has multiple binding sites
Which type of helper cells are generated during type 1 hypersensitivity reactions?
Th2 CD4
B cell helper follicular CD4 T cells
Which type of cytokines are released from Th2?
Type 2 cytokines IL-4 IL-13, Binds onto complementary receptors on B cells promoting B cell activation to produce antigen-specific IgE
Which cells express high-affinity IgE receptor(FC epsilon receptors)?
Granulocytes
What effect does IgE have on mast cells?
Mast cell degranulation
What is the end product of type 1 hypersensitivity?
Histamine release, cytokines recruit other cells
Th2 differentiation
Which cells are present at the later stages of a type 1 HS?
Th2 and eosinophils
Which receptor do IgE antibodies bind onto?
Fc Epsilon receptors
What are type 2 hypersensitivity reactions?
Antibody-mediated cytotoxic; destruction of body cells by IgG/IgM antibody bound to antigens present on cell surface membranes
Which antibodies are affiliated with type 2 hypersensitivity reactions?
IgG & IgM
What is a common RBC type 2 sensitivity reaction example?
Hemolytic disease of new-borns
Maternal Anti-D antibodies destroy fetal RhD+ cells.
What complement complex is formed upon antibody bound cell surface membranes?
Membrane attack complex (MAC)
What pathways are triggered through type 2 hypersensitivity reactions?
Antibody-dependent cell-mediated cytotoxicity: Cell lysis
Classical activation of the complement cascade
Lectin pathway
What is a type 3 hypersensitivity reaction?
Immune complex driven, arise from failed clearance of antibodies reacting against self-antigens
Immune complexes are removed by the immune system
What are immune complexes?
Non-cell bound antigen-antibody complexes
Provide an example of a self-antigen?
Nuclear DNA
What is promoted via the failure of the clearance of immune complexes?
Inflammation and tissue damage
Which immune cells are associated with type 3 hypersensitivity reactions?
Neutrophils+Macrophages
What is serum sickness?
Anti-serum (Antibodies specific to snake venom protein) are attacked by antibodies made by the body
What is a type IV hypersensitivity reaction?
Delayed T cell-mediated hypersensitivity is initiated by sensitized T cells.
Which immune cells are associated with type 4 hypersensitivity?
T cells
What is the sensitization phase?
Antigens are presented to Naive t cells by antigen-presenting dendritic cells, results in the generation of antigen-specific memory T cells.
What physiological process is promoted via type IV hypersensitivity reactions?
Inflammation
Why does contact dermatitis cause Type IV hypersensitivity?
Urushiol drives a T-helper create mem cells in 1st response, re-exposure results in memory cells producing cytokines (IFN gamma), promotes inflammatory activation of macrophages and causes edema.
Which type of hypersensitivity reactions is graft rejection associated with?
Type IV
Which type of hypersensitivity reaction is TB lesion associated with?
Type IV
Which type of reaction is Graves’s disease associated with?(Consider thyroid-stimulating antibodies)
Type II
