Lecture 14: Disorders in Immunity

Question 1

Hypersensitivity

Answer 1

Any immune response against a foreign antigen that is exaggerated beyond the norm

Question 2

Type 1 - Immediate hypersensitivity:

Answer 2

localized or systemic reactions
Result from the release of inflammatory molecules in response to an antigen
Develop within seconds or minutes following exposure to an antigen
Commonly called allergies and the antigens that stimulate them are called allergens
Atopy: chronic, local allergy
Anaphylaxis: systemic reaction, involving airway obstruction, can be fatal

Question 3

Type II - Antibody-mediated hypersensitivity:

Answer 3

Also called Cytotoxic hypersensitivity
Involve IgG or IgM antibodies and complement proteins
Results when cells are destroyed by an immune response
Is a component of many autoimmune diseases

2 significant examples:

Destruction of blood cells following an incompatible blood transfusion

Destruction of fetal red blood cells in hemolytic disease of the newborn

Question 4

Type III - Immune complex-mediated:

Answer 4

Due to the formation of antigen-antibody complexes, also called immune-complexes
Can cause systemic or localized reactions:

Question 5

Type III - Immune complex-mediated: Systemic:

Answer 5

Systemic lupus erythematosus

Rheumatoid arthritis

Question 6

Type III - Immune complex-mediated: Localized

Answer 6

Hypersensitivity pneumonitis

Individuals becomes sensitized when antigens are inhaled deep into the lungs, stimulating the production of antibodies
Subsequent inhalation of the same antigen stimulates the formation of immune complexes that activate complement

Glomerulonephritis

Immune complexes circulating in the bloodstream are deposited on the walls of glomeruli (small blood vessels in the kidneys)
Damage to the glomerular cells impedes blood filtration
Result is kidney failure and ultimately death

Question 7

Type IV - Delayed or T-cell mediated hypersensitivity:

Answer 7

Inflammation due to contact with certain antigens occurs after 12-24 hours
Result from the interactions of antigen, antigen-presenting cells, and T cells
Delay in this response reflects the time it takes for macrophages and T cells to migrate to and proliferate at the site of the antigen

4 examples:
Tuberculin response
Allergic contact dermatitis
Graft rejection
Graft versus host disease

Question 8

Are allergens antigens? Name 4 classes of allergens and examples for each.

Answer 8

Immediate hypersensitivity, commonly called allergies and the antigens that stimulate them are called allergens

4 classes:
Inhalants
Dust mites, pollen

Ingestants
Peanuts, shrimp

Contactants
Detergent, latex glove

Injectants
Bees, penicillin

Question 9

Mast cells:

Answer 9

Cytoplasm filled with large granules
Granules contain a mixture of potent inflammatory chemicals

Question 10

Basophils

Answer 10

Leukocytes that contain granules that stain with basophilic (basic) dyes

Granules filled with inflammatory chemicals similar to those in the mast cells

Sensitized basophils bind IgE and degranulate in the same way as mast cells

Question 11

Eosinophils:

Answer 11

Leukocytes that contain granules that stain with the dye eosin

Granules contain inflammatory mediators and leukotrienes that contribute to the severity of a hypersensitivity response

Mast cell degranulation stimulates the release of eosinophils that migrate to the site of mast cell degranulation where they can degranulate

Question 12

clinical signs of localized allergic reaction

Answer 12

Usually mild and localized

Site of the reaction depends on the portal of entry

Inhaled allergens may cause hay fever, an upper respiratory tract response

Marked by watery nasal discharge, sneezing, itchy throat and eyes, and excessive tear production

Commonly caused by mold spores, pollens, flowering plants, some trees, and dust mites

Inhaled allergens that are small may reach the lungs and causes asthma
Characterized by wheezing, coughing, excessive production of mucus, and constriction of the smooth muscles of the bronchi

Some foods may contain allergens
Cause diarrhea and other gastrointestinal signs and symptoms

Local dermatitis
Produces hives (urticaria) due to release of histamine and other mediators into nearby skin tissue and the leakage of serum from local blood vessels

Question 13

clinical signs of systemic allergic reaction

Answer 13

Degranulation of many mast cells at once causes the release of large amounts of histamine and inflammatory mediators

Acute anaphylaxis or anaphylactic shock can result

Clinical signs are those of suffocation:

Bronchial smooth muscle contracts violently
Leakage of fluid from blood vessels causes swelling of the larynx and other tissues

Contraction of the smooth muscle of the intestines and bladders

Must be treated promptly with epinephrine

Question 14

How can skin testing for atopic and anaphylactic sensitivity done

Answer 14

Map skin on forearm

Inject allergens intradermally as mapped

Appraise after 15 minutes: wheal (histamine) presence, wheal diameter (scale 0-4)

Question 15

Which antibody is involved in type II hypersensitivity

Answer 15

IgG and IgM antibodies are involved