Immunology Overview Quiz

Introduction to the Immune System

• The immune system is crucial for preventing infectious diseases and traumatic injuries.
• Historically, high death rates from infectious diseases like smallpox, diphtheria, pneumonia, measles, and scarlet fever were common.
• Death rates varied annually but were significantly higher in the past than in modern times.
• The death rate from infectious diseases has declined due to advancements in public health, sanitation, and vaccination.
  • Public health measures such as clean water, food, sewers, and pest control greatly reduced infectious disease death rates.
  • Vaccination programmes have also been crucial in eradicating some diseases.
• In 2016, in the U.S., heart disease and malignant neoplasms were the leading causes of death.

Risk of Death from Infectious Diseases

• Diphtheria: 5–10% death rate in adults, higher in children.
• Measles: 1–2 per 1000 (~0.15%).
• Pertussis: Approximately 0.66% worldwide.
• Polio: 5–15% with acute infection due to paralysis.

Recurrent Diseases and Pandemics

• Smallpox (Variola virus): Death rate as high as 30% (higher in infants). Eradicated in 1980 through vaccination.
• Black Death (Yersinia pestis): 1331 – 1353. Estimated to have killed 75–200 million globally.

Death in Modern Times (2016 in the U.S.)

• Top causes of death:
  • Heart disease (23.1%)
  • Malignant neoplasms (21.8%),
  • Accidents (5.9%)
  • Chronic lower respiratory diseases (5.6%),
  • Cerebrovascular diseases (5.2%).

Why Death Rates from Infectious Disease Declined

• Biggest reason: Improved public health measures, including clean water, food, sanitation, and pest control.
• Antibiotics and vaccination also played important roles, as shown by dramatic decline in diseases such as diphtheria, measles, and polio.

Antibiotics/Antivirals and Vaccination

• Antibiotics: Cure rate 69%, success rate (improvement) 92%.
• Vaccination: Significantly effective, saving millions of lives annually globally.

Death by Infection

• Most microbes are harmless.
• Pathogenic microbes have specific characteristics: evade immune defenses, exploit the host, damage cells.

The good of your immune system

• Provides resistance to infectious diseases (e.g., viruses, bacteria, fungi, protozoans, worms, larvae).
• Provides protection against non-infectious diseases (e.g., cancers).
• Promotes wound repair after tissue trauma/injury.

The bad of your immune system (immunopathology)

• Can attack the body directly (e.g., autoimmune diseases).
• Can attack harmless substances (e.g., allergies).
• Can be destructive when overactive (e.g., tissue damage during inflammation).
• Attacks transplanted tissues.
• Reduces life expectancy.

Examples of Pathogens

• Viruses: Intracellular
• Prokaryotes (bacteria): Some intracellular, some extracellular, some both.
• Small eukaryotes (fungi, protozoans): Some intracellular, some extracellular, some both.
• Helminths (worms): Extracellular.
• Larvae: Extracellular.
• Ectoparasites (e.g., ticks, mosquitoes, flies): Extracellular; vectors for other pathogens.

Intracellular vs. Extracellular Locations for Pathogens

• Extracellular: Remain outside host cells. Some can be taken up by phagocytosis.
• Intracellular: Survive within host cells (e.g., cytosol, vesicles).

Viruses Are Among the Most Serious Pathogens

• Smaller than cells; cannot survive independently.
• Require host cells for propagation.
• Obligatory intracellular pathogens.
• Hijack host cell machinery to disrupt normal function
  • Infecting preferred cell types (tropism).
  • Using infected host cells to reproduce.
• Causing a range of disease outcomes (from no symptoms/low-level disease to severe cell damage and death).
• Unique molecular patterns

General Adverse Health Risks of Antibiotics and Vaccines

• Antibiotics adverse effects include: diarrhea, nausea, vomiting, rash, yeast infections, allergic reactions, dizziness, photosensitivity, rarely life-threatening C. difficile infection.
  • Anaphylaxis in variable up to 0.04% for penicillin with 10%.
• Vaccines adverse effects: pain, redness, swelling at injection site, fever, muscle/joint aches, headache, fatigue, nausea. temporary localized allergic reactions.
  • Anaphylaxis ~1 per million vaccinations. and 5 deaths in 10 years.
  • Vasovagal syncope (associated with needle stick) -- one reported death.

Other topics

• Information on various types of pathogens (bacteria, viruses, fungi, protists, and worms) and their infectious diseases were covered.