Immune Hypersensitivities Flashcards
Immune hypersensitivity is defined as…
Tissue damage due to an immune mechanism
Which hypersensitivity is involved with allergic reactions?
Type 1
Uses IgE, mast cells and eosinophils
Which hypersensitivity reaction is due to antibody binding to cell surface proteins?
Type 2
Which hypersensitivity reaction involves the immune complex desposition in tissue with compliment activation of inflammation?
Type 3
Which hypersensitivity reaction involves T cells ingested or mediated tissue damage?
Type 4
What are the three phases of mechanism of type 1 (atopy)?
Sensitization
Immediate Reaction
Late-Phase response
What is the basic process of a type 1 hypersensitivity reaction?
Allergen protein enters the body, TH2 cells are stimulated to get IgE cells which goes to the mast cells to release cytokines to call the eosinophils to do damage
What is sensitization in type 1?
The initial exposure to the allergic producing IgE
What happens in the immediate reaction in type 1?
Mast cell degranulation
What happens in the late-phase response in type 1?
Late reaction hours later by cytokines
What are the clinical manifestations of type 1?
Allergic rhinitis, sinusitis
Food allergies
Bronchial asthma
Anaphylaxis
What stimulates mast cell activation and degranulation?
Antigen cross-linked IgE/FcER
When an allergen is taken by the IgE to the Fc recepor, what pathways may occur?
Degranulation
Secreted cytokines
Membrane phospholipids
The granules that are released from the mast cell contain;
Histamine
Proteases
Chemotactic factor (ECF, NCF)
The membrane phospholipids make;
Arachidonic acid and PAF
What are the functions of TNF?
Inc vascular permiability …
What is the infiltrate of allergic reactions?
Mononuclear cells and eosinophils
What is the purpose of skin testing?
To identify specific allergens to which a patients reacts
How does a skin test work?
Inject a small amount of allergen into skin
Allergen binds to anti-allergen IgE on skin mast cells
Mast cell degranulates including vasodilation and vascular permeability
What is wheal?
Fluid filled bump on the skin
What is flair?
Erythema
What are the components of type Ii hypersensitivity?
Opsonization
Complement-mediated cell or tissue damage
Altered signaling if antigen is a cell-surface receptor
IgE or IgM
How does hemolytic anemia occur in type II?
Autoantibody to RBC surface antigens bind, compliment is activated coating cells with C3b causing cells to be phagocytized through spleen and splenic macrophages
If a mother is Rh- and her first baby is Rh+ what happens? What about her second Rh+ baby?
She will form Rh antigens during delivery
The second baby will be attacked by the Rh antigens causing death or a baby with hemolytic anemia
What is pemphigus vulgaris and how does it occur in type II rxns?
Skin disease causing layers of skin to separate at the desmosomes causing large skin blisters
And antibody to the desmosome cadherin dsg3 on keratinocytes causes keratin retraction, actin cytoskeleton remodling and loss of cell to cell adhesion
What is the anti-basement membrane disease in type II rxns?
Antibodies attack basement membrane collagen in glomeruli and lungs
C5a and C3a try to phagocize but due to the large structure instead do frustrated phagocytosis causing extensive tissue damage
How does graves disease work?
Antibody against thyroid stimulating hormone which over -stimulates it making it impossible for thyroid hormone to down regulate itself
Cause hyperthyroidism
How does myasthenia gravis work?
Blocks ACh receptor so that the muscle cannot contract causing profound muscle weakness
What are some characteristics of type III hypersentivity reaction?
Immune complex formation
Only use IgG
Antiggens can be autologous or microbial in origin
Deposits in tissues
What is the infiltrate of type III rxns?
Neutrophils
Destruction by neutrophils
Where are locations that normally are seen in a type III rxn?
Glomeruli, joints, arteries and skin
What is the mechanism of disease for systemic lupus erythematosus?
Complement and Fc receptor mediated inflammation causing nephritis, arthritis and vasculitis
The antibodies attack DNA and nucleoproteins
What characterized a type IV hypersentivity reaction?
Extensive tissue damage to cells instigated to CD4 T cells and activated macrophages and cytotoxic T cells
What is the infiltrate of type IV rxns?
Mononuclear cells into affected tissue
