Autoimmune & Hypersensitive Rxns

Question 1

What are the 4 Major types of Autoimmune Disorders &Hypersensitivity Reactions?

Answer 1

*Type I Hypersensitivity
“Allergies”
*Type II Hypersensitivity
Reactions to Self-Antigens
*Type III Hypersensitivity
Immune Complex Formation
*Type IV Hypersensitivity
Cell-Mediated

Question 2

What is IgE?

Answer 2

immunoglobulin

Question 3

Describe the histology of an allergic response.

Answer 3

Occur within minutes of exposure to antigen
Antigens combine with IgE antibodies
IgE binds to mast cells and basophils, causing them to undergo degranulation and release several chemical mediators:
Histamine: dilates and increases permeability of blood vessels (swelling and redness), increases mucus secretion (runny nose), smooth muscle contraction (bronchi).
Prostaglandins: Contraction of smooth muscle of respiratory system and increased mucus secretion.
Leukotrienes: Bronchial spasms.

Question 4

What is stridor?

Answer 4

kind of croup sound, with breath

Question 5

What are some symptoms of Anaphylaxis

Answer 5

Swelling of conjuctiva, runny nose, swelling lips and throat, lightheaded, unconsciousness, confusion, headache, anxiety, bradycardia or tachycardia, hypovolemia, skin (hives, flushing, itching), shortness of breath, weezing, stridor, diarrhea, vomiting, cramps, loss of bladder control.

Question 6

Common food triggers of anaphylaxis?

Answer 6

Foods
Wasp/bee stings
Medications
Exercise

Question 7

What are medications for anaphylaxis?

Answer 7

epinephrine (emergent); corticosteriods; antihistamines; IV fluids/ airway protection

Question 8

Describe Type II (Cytotoxic) Reactions?

Answer 8

Involves antibodies (IgG or IgM) binding to antigens on the cell surface
Antigen may be intrinsic (i.e.: “self”) OR extrinsic (adsorbed onto the cells during exposure to some foreign antigen/ pathogen)
Antigenic cell is lysed/ phagocytized
Examples: transfusion reactions; Graves Disease; Myasthenia Gravis

Question 9

What is Graves Disease ?

Answer 9

hyperactive thyroid, producing an excessive amount of thyroid hormones
Antibodies attach to TSH receptors on thyroid gland stimulating production & secretion of thyroid hormone
Hyperthyroidism

Question 10

what is Myasthenia Gravis?

Answer 10

Neuromuscular disease leading to weakness & rapid fatigue

Antibodies blocks postsynaptic acetylcholine receptors, disrupting neuromuscular transmission

Question 11

Describe Type III (Immune Complex) Reactions

Answer 11

Involve reactions against soluble antigens circulating in serum. Usually involve IgG & IgM antibodies. Antibody-Antigen immune complexes are deposited in blood vessels, joints and renal glomeruli resulting in symptoms.
Complexes activate complement.
Result –> prolonged inflammation with resultant damage. Common Disorders:
Systemic lupus erythematosus (SLE)
Rheumatoid arthritis (RA)
Extrinsic allergic alveolitis (Hypersensitivity pneumonitis)
Glomerulonephritis

Question 12

What is Systemic Lupus Erythematosus (SLE)?

Answer 12

Multisystem autoimmune disease
Diffuse inflammation involving 
Skin, joints, brain, kidneys, heart, lungs, serous membranes
Common symptoms:
Skin:  rash (malar rash=butterfly rash)
Eyes:  photosensitivity
Neurologic:  headaches; memory loss
Musculoskeletal:  persistent joint pain & swelling
Extremities:  Raynaud’s
Fatigue & Obesity
Osteopenia/osteporosis

Question 13

what are the Demographics of SLE?

Answer 13

Age: 15-45 years peak frequency
15-20% are children and have worse disease
Sex: 9:1 F>M
1 in 250 African-American females
Males have worse disease
Race: Nonwhite/white ratio 3:1
Nonwhites have worse disease
Total number: 1.4 million (250,000 severe)

Question 14

What does SLE do to the heart?

Answer 14

Vasculitis (inflammation) affecting coronary arteries  Atherosclerosis/ CAD
↑ risk for conduction abnormalities (dysrhythmias)
HTN: ↑ risk for cardiomegaly & heart failure

Question 15

What does SLE do to the Lungs?

Answer 15

Pleuritic chest pain
Interstitial lung disease
Decreased diffusion capacity and restrictive pattern on PFT’s
Diaphragmatic weakness leading to dyspnea

Question 16

Should patients with SLE exercise?

Answer 16

Exercise yes! Good outcomes for strength, endurance etc.

Question 17

Describe Type IV Delayed (Cell-Mediated) Reactions.

Answer 17

Not antibody mediated but cell mediated
Involve reactions by memory cells.
First contact sensitizes person.
Subsequent contacts elicit a reaction.
Reactions are delayed by one or more days (“delayed hypersensitivity”).
Delay is due to activation/ migration of macrophages and T cells to site of foreign antigens.
Reactions are frequently displayed on the skin: itching, redness, swelling, pain.
Tuberculosis skin test (Mantoux screening test/ PPD (purified protein derivative)
Poison ivy
Metals
Latex (3% of health care workers)
Anaphylactic shock may occur.

Question 18

Describe the pathogenesis of type IV hypersensitivity?

Answer 18

Sensitization Phase:
Step 1: antigen absorbed by the skin (or injected)
Step 2: APC (e.g.: dendritic cell; macrophages) process antigen
Effector Phase:
Step 3: Previously sensitized cells recognize antigen on 2nd presentation
Step 4: Macrophages/ cytotoxic T cells attracted to site
Step 5: Activated macrophages/ cytotoxic T cells cause inflammation by releasing cytokines & toxic chemicals locally resulting in damage