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.