Allergy and Hypersensitivities Flashcards
List the four types of hypersensitivity reactions of the immune system.
IgE mediated
IgG mediated cytotoxic
Immune complex mediated
Cell-mediated
Describe IgE mediated hypersensitivity in function and it’s outcomes.
IgE is bound to mast cells via Fc and when an allergen binds to these Abs it crosslinks IgE and induces degranulation.
Causes localized and systemic anaphylaxis, seasonal allergies, food allergies, etc.
Describe IgG mediated cytotoxic hypersensitivity in function and it’s outcomes.
Cells destroyed by bound antibodies either by activation or compliment by CTL with an Fc receptor for ADCC
RBCs destroyed by complement and Abs during transfusion of mismatched blood type or during erythroblastosis fetalis.
Describe immune complex-mediated hypersensitivity in function and it’s outcomes.
Ag-Ab complexes deposited in tissues causing activation of complement which attracts neutrophils.
Most commonly seen in glomerulonephritis, RA, and systemic lupis.
Describe cell-mediated hypersensitivity in function and it’s outcomes.
Th1 cells secrete cytokines which activate macrophages and CTLs and can cause macrophage accumulation.
Commonly contact dermatitis, tuberculin reaction, autoimmunity such as diabetes mellitus type I, MS, and RA
Define allergen.
Define antigen.
Antigen which elicits hypersensitivity or allergic reactions.
Antibody generating protein. A substance that stimulates an immune response.
What are the main Th2 responses geared towards?
How do Th2 cells do this?
Eliminating parasites
Th2 cytokines promote production of IgE and B cells. IgE binds Fc receptors on surface of effectors and activates them with Ag. Epithelial cells stimulated can promote wound repair or encapsulate worms.
What kind of hypersensitivity is allergy?
Type I hypersensitivity - IgE mediated
What is atopy?
Atopy refers to one’s predisposition to produce IgE against common environmental antigens. Allergens often have multivalent epitopes and have enzymatic activity and modulate immune responses. They often contain PAMPs and are found at low concentrations in mucosa which pre-disposes to Th2 responses (slide 9, lec 23)
What drives atopic reactions? How?
IgE and Th2 cytokines. Degranulation of mast cells, basophils, eosinophls, and neutrophils causes inflammation, changes in stromal cell function, and tissue remodelling.
What is the allergic triad?
Atopic dermatitis, allergic rhinitis, and asthma
In asthma, how is airway constriction mediated?
Inflammation, mast cell degranulation, stimulation of nerve fibers, sm muscle contraction, and mucus production.
Describe epithelial cells.
They are evolutionarily the first line of defense against infection. Report tissue damage via danger signals and are an important first step in the initiation of an immune response.
What are some common triggers that induce altered states in epithelium?
Viral, bacterial, and fungal infections
Allergen exposure
Pollutant exposure and cigarette smoke
Asthmatic airways show signs of what??
Tissue damage and impaired repair.
