Chapter 14 - Type I Allergies

hematopoiesis

creation of cellular components of blood

stem cells

all blood cells arise from these

myeloid stem cell

these make granlocytes

lymphoid stem cells

these make agranulocytes

human immune system

powerful and a necessary system of defense, with the potential to cause injury and disease

abnormal immune functions

What are asthma, diabetes, rheumatoid arthritis, and graft rejection caused by?

immunopathology

the study of disease states associated with the overreactivity or underreactivity of the immune response

hypersensitivity (overreactivity)

Allergy and autoimmunity; The tissues are innocent bystanders attacked by immune components that can’t distinguish one’s own tissues from foreign material

hyposensitivity (immunodeficiency)

Immune system is incompletely developed, suppressed, or destroyed

type I

immediate hypersensitivity; IgE mediated, involves mast cells, basophils, and allergic mediators; “common” allergy and anaphylaxis

type II

antibody mediated; IgG, IgM antibodies plus complement act opon cells and cause cell lysis; some autoimmune diseases; blood group incompatibility, pernicious anemia, myasthenia gravis

type III

immune complex mediated; antibody mediated inflammation; circulating IgG complexes deposited in basement membranes of target organs; includes some autoimmune diseases; systemic lupus erythematosus, rheumatoid arthritis, serum sickness, rheumatic fever

type IV

T-cell mediated; delayed hypersensitivity and cytotoxic reactions in tissues; includes some autoimmune diseases; infection reactions, contact dermatitis, graft rejection

type I-III

these are B cell-IgG type responses

allergy

exaggerated immune response; causes inflammation

allergens

antigens that induce allergy in sensitive individuals

atopy

chronic local allergy (i.e. hay fever or asthma)

anaphylaxis

systemic, sometimes fatal, reaction that involves airway obstruction and circulatory collapse

half

How much of the US population is affected by airborne allergies?

T/F: Asthma and some food allergies may require hospitalization and can cause death (type I)

outgrown

Some type I allergies last for a lifetime, some are “_______,” and others develop later in life

generalized susceptibility

_________ ________to allergens is inherited, not the allergy to a specific substance

• i.e. parent with cat hair allergy may have child with pollen allergy

25, 50

The prospect of a child developing an atopic allergy is ___% if parents are afflicted and ____% if siblings or grandparents are also afflicted

increased IgE production, increased reactivity of mast cells (granular leukocyte), increased susceptibility of target tissue to allergic mediators

What is the genetic basis for atopy?

hygiene hypothesis

• Immune systems need to be “trained” by interaction with microbes as we develop

• But the industrialized world has created a hygienic environment (antimicrobials, well-insulated homes, etc.)

• Children who grow up on farms have lower incidences of several types of allergies

• Delivery by cesarean section and maternal history of allergy elevates childhood risk of allergy by a factor of eight

cytokines

Newborns only breast fed for the first 4 months have a lower risk of asthma and eczema

• _______ and growth factors in human milk act on the baby’s gut mucosa to induce tolerance to allergens

600

_______ species of bacteria can be transferred to infants through breast milk

• Important role in the development of tolerance to foreign antigens

proteins

_______ are more allergenic than carbohydrates, fats, or nucleic acids

mucosa of the gut and respiratory tract and skin

What are the main type I portals of entry?

mucosa of the gut and respiratory tract

Thin, moist surface that is normally penetrable

skin

• Dry, tough keratin is generally less permeable

• Access occurs through tiny breaks, glands, and hair follicles

inhalants

airborne environmental allergens such as pollen, house dust, dander, or fungal spores

ingestants

allergens that cause food allergies

injectants

allergies triggered by drugs, vaccines, or bee venom

contactants

allergies that enter through the skin

IgE

monomer; bound to mast and basophils throughout the body, blood; functions in allergic reactions, possibly lysis of parasitic worms

hay fever (allergic rhinitis)

name the IgE Mast-Cell Mediated Allergic Condition:

• Seasonal reaction to inhaled plant pollen or molds

• Chronic, year-round reaction to airborne allergens or inhalants

• Targets: respiratory membranes

• Symptoms: nasal congestion; sneezing; coughing; profuse mucus secretion; itchy, red, and teary eyes; mild bronchoconstriction

asthma

name the IgE Mast-Cell Mediated Allergic Condition:

• Respiratory disease characterized by episodes of impaired breathing due to severe bronchoconstriction

• Airways are extremely sensitive to small amounts of inhalants, ingestants, or other stimuli, such as infectious agents

• Symptoms range from bouts of difficult breathing to fatal suffocation

atopic dermatitis/eczema

name the IgE Mast-Cell Mediated Allergic Condition:

• Intensely itchy skin inflammation

• Sensitization occurs through ingestion, inhalation, and skin contact with allergens

• Usually begins in infancy and is characterized by reddened, encrusted skin lesions

• Progresses to a dry, scaly, thickened skin condition in adults

food allergy

name the IgE Mast-Cell Mediated Allergic Condition:

• Most common food allergens: peanuts, fish, cowʼs milk, eggs, shellfish, soybeans

• Intestinal entry

• Symptoms include vomiting, diarrhea, and abdominal pain

• Other manifestations include hives, asthma, and occasionally anaphylaxis

drug allergy

name the IgE Mast-Cell Mediated Allergic Condition:

• One of the most common side effects of treatment, affecting 5-10% of hospitalized patients

• Reactions range from mild rash to fatal anaphylaxis

• Compounds implicated:

  • Antibiotics: penicillin

  • Synthetic antimicrobials: sulfa drugs

  • Aspirin

  • Opiates

  • Contrast dye used in X rays

rales

clicking, bubbling, or rattling sounds in the lungs

anaphylaxis

swift reaction to allergens

cutaneous anaphylaxis

wheal-and-flare inflammatory reaction to the local injection of allergen

systemic anaphylaxis

characterized by sudden respiratory and circulatory disruption that can be fatal within minutes due to airway blockage

• Often due to bee stings and injection of antibiotics or serum

• Result of the sudden, massive release of chemicals into the tissues and blood, which act rapidly on target organs

blood testing

What type of tests are In Vitro Methods?

radioallergosorbent test (In Vitro)

measures levels of IgE to specific antigens

tryptase test (In Vitro)

measures enzyme (tryptase) released by mast cells during allergic response

In Vitro

Is this In Vitro or In Vivo: Differential blood cell count

Leukocyte histamine-release test (In Vitro)

measures histamine released from basophils after  allergen exposure

skin testing

in vivo method to detect precise atopic or anaphylactic sensitivities

• Skin is injected, scratched, or pricked with a small amount of pure allergen extract

• A wheal-and-flare result 20 minutes after antigenic challenge is indicative of histamine release

• The diameter of the wheal is measured and rated on a scale from 0 (no reaction) to 4 (greater than 15 mm)

1. blocking the processes of allergy

Which step in treating allergies is the following: Take drugs that block the action of lymphocytes, mast cells, or chemical mediators

step 1

Which step in blocking the processes of allergy is the following:

• steroids shut down IgE production

step 2

Which step in blocking the processes of allergy is the following:

• antibodies keep IgE from mast cells

step 3

Which step in blocking the processes of allergy is the following:

• cromolyn prevents degranulation

step 4

Which step in blocking the processes of allergy is the following:

• antihistamines counteract effect of cytokines on target cells

step 2

Which step in treating allergies is the following: avoid the allergen

densensitization

Which step in treating allergies is the following: densensitization

• IgG produced in response to allergen

• in subsequent exposures, IgG binds allergen before it can bind to IgE on mast cells, stopping degranulation

desensitization

controlled exposure to the antigen to reset the allergic reaction

IgG

monomer; found in blood, lymph, intestine; enhances phagocytosis, neutralizes toxins and viruses, protects fetus and newborn

IgM

pentamer; locations are blood, lymph, B cell, surface; especially effective against microorganisms and agglutinating antigens; first antibodies produced in response to initial infection

mast cells

Located in all connective tissues (high numbers in lungs, skin, genitourinary and GI tracts)

first allergen exposure

Mast cells in Type I Allergy: After _____ _______ _______ (sensitization), mast cells bind IgE. 

degranulate

Mast cells in Type I Allergy: In future exposures, allergen binds IgE, then mast cells _______ (release cytokines)

target organs

Mast cells in Type I Allergy: Symptoms are due to effects of host immune molecules on _____ ______ (not the direct action of allergen)

prostaglandin

What cytokine impacts these targets: dilated blood vessel, constricted bronchioles, nerve cell, headache

leukotriene

What cytokine impacts these targets: constriction of bronchioles, airway obstruction, mucus buildup, asthma

histamine

What cytokine impacts these targets: increased blood flow, skin manifestations

serotonin

What cytokine impacts these targets: increased peristalsis of intestine, diarrhea, vomiting

bradykinin

What cytokine impacts these targets: increased secretions from glands on epithelial tissue