Immune System Pathology

Question 1

Pathologies of the Immune System

Answer 1

• Hypersensitivity reactions
• Autoimmune disorders
• Immunodeficiencies

Question 2

Hypersensitivity Disorders

Answer 2

• Hypersensitivity: disproportionate reactivity to an antigen.
• Hypersensitivity reaction: Immune responses to harmless antigens that cause symptoms upon re-exposure.
• Hypersensitivity disease: persistent and recurrent reaction to harmless antigen.

Question 3

Type I Hypersensitivity - Steps

Answer 3

Immediate hypersensitivity. Reaction to common allergens.
Two step reaction:
1. Sensitization: IgE antibodies bind to mast cells
2. Subsequent exposure: Allergen binds to mast cell → degranulation → release of histamine → bronchospasm, vasodilation and increased permeability.
Causes localized and systemic anaphylaxis.

Question 4

Type I Hypersensitivity - Symptoms

Answer 4

• Allergic rhinitis: most common, 10-30% of the population
Symptoms:
- Runny or stuffy nose
- Sneezing
- Red, itchy, and watery eyes
- Swelling around the eyes

Question 5

Anaphylaxis - Description and Cause

Answer 5

Life-threatening emergency, immediate epinephrine injection.
Exposure to large quantity of allergen.
Wide spread release of histamine → Increase vasodilation + airways constriction (drop in blood pressure).
Cause: Insect bites, stings. Food ingestion. Medication.

Question 6

Type I Hypersensitivity - Treatment

Answer 6

• Anti-histamines: counteract histamine effects
• Corticosteroids: reduce inflammation (standard treatment)
• Epinephrine: induce vasoconstriction (prevent anaphylactic shock)

Question 7

Type II Hypersensitivity - Description and Process

Answer 7

Cytotoxic hypersensitivity: antibody mediated destruction of healthy cells. Slightly delayed response (2-24h).
IgG antibodies recognize specific antigen and bind to a host cell:
a) Phagocytosis
b) Activation of compliment system (neutrophils, lytic death
c) Cellular dysfunction

Question 8

Myasthenia Gravis (Type II) - Process

Answer 8

Antibody directed against nicotinic receptor.

Nerve impulse of motor neuron fail to pass the neuromuscular junction and stimulate contraction.

Question 9

Myasthenia Gravis (Type II) - Symptoms

Answer 9

Slow progressive disease with fluctuations in symptoms.
- Double vision and dropping eyelid
- Fatigue while chewing
- Open jaw
- Difficulty swallowing
- Trouble talking & walking
Myasthenic crisis: Life-threatening, weakening resp. muscles

Question 10

Type III Hypersensitivity - Process

Answer 10

Immune complex - mediated reaction: compliment activation and inflammatory reaction. Hours or days.
Antigen-antibody complexes deposit on basal lamina of blood vessels → Activation of compliment → Inflammation → Neutrophil degranulation and tissue damage.
Result: Vasculitis (skin, kidneys, joints, pleura, pericardium).

Question 11

Systemic Lupus Erythematosus (Type III) - Symptoms

Answer 11

Antibodies against DNA and nuclear proteins.

• Rashes of the skin (UV exposure)
• Myalgia
• Polyarthritis
• Inflammation in the heart, lungs and kidneys

Question 12

Type IV Hypersensitivity

Answer 12

T-cell mediated hypersensitivity. 24-72 hours from exposure.
CD8+ (cytotoxic) mediated: directly kills target cells. e.g. Type I diabetes.
CD4+ (t helper) mediated: T helper cells activate macrophage → secrete pro-inflammatory cytokines that damage tissues.
e.g. Multiple sclerosis.

Question 13

Multiple Sclerosis - Description and Symptoms

Answer 13

Inflammatory disorder in CNS that compromises integrity of blood brain barrier. Irreversible axon loss and cell death that causes brain atrophy.

• Fatigue
• Pain
• Weakness & balance problems
• Sensory loss
• Visual dysfunction
• Spasticity and spasms
• Depression

Question 14

Autoimmune Disease - Description and Treatment

Answer 14

Loss of tolerance towards self-antigens.
Treatment: corticosteroids & NSAIDs
Physical therapy if the disease impacts bones,
joints, or muscles.

Question 15

Primary Immunodeficiency

Answer 15

Congenital conditions. Mutation to genes affecting the functioning of immune cells.

Question 16

Secondary Immunodeficiency

Answer 16

Acquired. Various factors reduce the effectiveness of the immune response in an intrinsically normal immune system.

Question 17

What can immunodeficiency lead to?

Answer 17

• Frequent and unusual (bad) complications of common infections (e.g. pneumonia)
• Opportunistic infections
• Increase prevalence of tumors.

Question 18

Corticosteroids

Answer 18

Commonly prescribed to decrease inflammation.
Reduced production of pro-inflammatory cytokines and even lymphocytes in high dosage.
Can cause immunosuppression after prolonged usage.

Question 19

HIV - Transmission and Description

Answer 19

Unprotected sexual intercourse and sharing needles.

HIV is a retrovirus: its genome is integrated in the DNA of CD4 T-cells → Infected T cells will produce new HIV viruses.

Question 20

HIV - Progression

Answer 20

1. Acute infection
2. Latent period: asymptomatic HIV disease
3. Early symptomatic HIV disease
4. Advanced HIV disease or AIDS

Question 21

HIV - Clinical Manifestation in Acute Infection

Answer 21

• Initially high viral load
• Production of antibodies (3-6 weeks)
• Reduction of circulating virus
  Symptoms:
• flu-like symptoms
• lymphadenopathy

Question 22

HIV - Clinical Manifestation Latent Period

Answer 22

• No clinical symptoms
• Positive antibody test for HIV
• Without treatment it can last anywhere between 1 to 20 years.

Question 23

HIV - Clinical Manifestation Early Symptomatic HIV Disease

Answer 23

• Persistent generalized lymphadenopathy
• Oral lesions
• Reactivation of shingles
• Hematological disturbances

Question 24

HIV - Clinical Manifestation Advanced HIV Disease (AIDS)

Answer 24

• Neurological manifestation
• Weight loss
• Opportunistic infections
• Malignancies
• Fatigue
• Dermatological conditions

Question 25

HIV - Treatment and Prognosis

Answer 25

Highly active antiviral therapy (HAART)
Manageable chronic illness for patients having access to
treatment and adhere to treatment.