Hypersensitivity

Hypersensitivity

abnormal immune response to an external antigen that causes damage to the body

Type 1

hypersensitivity aka immediate hypersensitivity or allergies, occurs in seconds to minutes

IgE

antibody that drives type 1 hypersensitivity

Mast, basophils, eosinophils

cells that drive type 1 hypersensitivity IgE response

Inhaled, injected, ingested, contact

four methods of type 1 hypersensitivity exposure

Rhinitis, asthma

symptoms of inhaled allergens that cause a type 1 hypersensitivity reaction

Systemic anaphylaxis

symptoms of injected allergens that cause a type 1 hypersensitivity reaction

Vomiting, diahhrea

symptoms of ingested allergens that cause a type 1 hypersensitivity reaction

Rashes, edema, eczema

symptoms of contact allergens that cause a type 1 hypersensitivity reaction

Degranulation

mechanism of mast, baso, eosinophils

1

type ___ mechanism: DC ingest allergen then traffic to draining LN, Tfh are activated make Th2 cytokines like IL4/5, activated B cells switch to IgE, IgE bind to Fc receptor on mast, baso, eosinophils, triggering release of granules that cause the allergic reaction

IL4/5

cytokines that trigger B cell class switching to IgE production

Activation

the severity of the reaction depends on the site of _ (type 1 hypersensitivity reaction)

Local

inhalation results in a ___ release of histamine in type 1 hypersensitivity reaction

Mucus

inhalation and local inflammation results in swelling of sinuses and the release of ___ in a type 1 hypersensitivity reaction

Systemic

injection or ingestion results in a ___ release of histamine type 1 hypersensitivity reaction

Vascular permeability, drop in blood pressure, death

effects of systemic inflammation caused by histamine release from injection or ingestion in type 1 hypersensitivity reaction (aka anaphylaxis)

Anaphylaxis

symptoms of ____ include hives, itching, flushed or pale skin, low bp, constricted airways, weak rapid pulse, nausea, fainting

Epinephrine

treats anaphylaxis (need to seek medical care after dispensing in pt)

Allergen testing

pt are pricked in the back with potential allergens and wheal and flare response indicates type 1 hypersensitivity

Avoidance, symptom treatment, allergy shots

treatment options for type 1 hypersensitivity

Omalizumab

anti IgE drug

Allergy shots

regular _ reduce allergy attacks, takes years (3-5), subcutaneous low dose : mechanism ; enhance Treg production, increase antigen specific IgG, inhibit Th2 t cell and IgE production

Type 2

aka cytotoxic hypersensitivity, ab response against foreign allergens that attach to otherwise healthy cells, takes minutes to hours, elicits Ab dependent cellular cytotoxicity

IgG, IgM

ab that mediate a type 2 hypersensitivity reaction

Transfusion reaction

example of a type 2 hypersensitivity reaction where incompatible ___ leads to lysis of RBC and maybe death

Hemolytic disease of newborns

example of a type 2 hypersensitivity reaction where Rh- mothers cause hemolysis in their second Rh+

Type 3

IgG mediated, all antivody response form aggregates with soluble antigen, but when antigen is in excess smaller aggregates can escape compliment clearance and deposit in blood vessel walls, these deposits engage with Fc receptors and cause damage to vessels (Arthus reaction)

Serum sickness

example of type 3 hypersensitivity reaction

Type 4

t cell mediated against peptides derived from allergens, occurs days after allergen exposure, delayed type hypersensitivity, effector t cell activation causes tissue damage

Poison ivy

example of type 4 hypersensitivity reaction (common example of contact dermitis), cd8 t cell mediated, urushiol oil is the Allergan

DTH skin tests

caused by type 4 hypersensitivity reactions