Exam Notes

Exam Preparation

General Exam Information

• Paragraph-based questions are common, requiring the ability to identify important information.
• The upcoming exam will be more challenging.
• The exam is cumulative, covering material from day one through exercise 12.
• Virtual lab information is available online.

Lab Report

• Acceptable sources:
  • Burgey's Manual (primary source)
  • Lab manual
  • OpenStax
  • Peer-reviewed journal articles (primary articles only; no reviews, Mayo Clinic, or WebMD).
• Lab instructors and the professor are available for review this week.

Class rules

• Writing on lab benches will result in a zero grade for the entire class on lab exams.

Innate Immune System

• Features:
  • Present from birth.
  • Always active.
  • No memory.
  • Non-specific.
• First Line of Defense:
  • Physical barriers: Skin.
  • Chemical barriers: Sebum.
• Second Line of Defense:
  • If infection occurs
    • Chemotaxis, adherence, ingestion, digestion.

Inflammation

• Important to inflammation.
• Involves vasodilators.
• Vasodilation: Increases blood vessel diameter, allowing more white blood cells to reach the infection site quickly, also increases permeability.
• Diapedesis: Process of white blood cells moving out of the blood vessel.

Fever

• Abnormally high body temperature.
• Normal hypothalamus set point: 37 degrees Celsius.
• Conversion between Celsius and Fahrenheit is necessary for the exam.
• Cytokines raise the set point in the hypothalamus during injury, maintaining the higher temperature until released.

Antimicrobial Substances

• Proteins part of the second line of defense.
• Examples:
  • Complement system
  • Interferons
  • Antimicrobial peptides

Complement System

• Complements both innate and adaptive immunity.
• Consists of 30 proteins made by the liver.
• Present in blood serum and circulate throughout the body.
• Can be recruited by the adaptive immune system.
• Functions:
  • Destroying microbes via:
    • Cytolysis (cell rupture)
    • Opsonization (targeting cells for phagocytosis)
    • Inflammation (enhancing existing inflammation)
• Proteins are inactive until split into active fragments.
• Complement proteins are named with an uppercase C and numbered 1-9 in order of discovery (e.g., C3).
• Activated fragments are indicated with lowercase letters (e.g., C3a, C3b).

C3 Activation

• C3 splits into C3a and C3b upon activation.
• C3 triggers a cascade leading to cytolysis.
• C3b coats microbes, enhancing phagocytosis.
• C3a causes inflammation.

Classical Pathway

• Initiated by microbes with antigens.
• Antibodies attach to antigens.
• Involves C1, C2, and C4, leading to C3.

Alternative Pathway

• Involves lipid-carbohydrate complexes on the microbe surface and proteins B, D, and P.
• Bypasses C1, C2, and C4, directly activating C3.

Lectin Pathway

• Macrophages ingest bacteria or viruses and release cytokines.
• Cytokines trigger the liver to produce lectins (mannose-binding lectin).
• No antibodies are involved; relies on phagocytosis
• Lectins bind to carbs, leading to C3 activation.

Common Endpoint

• Regardless of the pathway (classical, alternative, lectin), the end goal is the same: C3 activation.

Cytolysis

• C3 activates complement C5.
• C5 splits into C5a and C5b.
• C5b recruits C6, C7, C8, and C9 to form the Membrane Attack Complex (MAC), puncturing the microbe's membrane, leading to cell lysis

Opsonization

• C3b coats the microbe, enhancing phagocytosis.

Inflammation (Role of C3a and C5a)

• C3a and C5a contribute to inflammation.
• C5a binds to C5a receptors on mast cells.
• C3a causes mast cells to release histamine, promoting inflammation.
• C5a functions as a chemotactic factor for phagocytes.

Interferons

• Chemicals produced by cells with antiviral activity.
• Interfere with viruses.
• Interferon alpha and beta are produced in response to viral infections.
• Mechanism:
  • Alert neighboring cells to produce antiviral proteins that inhibit viral replication.
  • Virus invades cell, leading to transcription and translation.
  • Interferons signal to neighboring cells to produce antiviral proteins, blocking virus replication.
• Used for treatment of hepatitis, but come with harsh side effects.