Ch22A_immune_system

Chapter 22A: The Immune System Overview

• Overview of the Immune System

  • Infectious Agents: Pathogenic organisms that invade the body.

  • Innate vs Adaptive Defense Systems: Two key components of immune response.

  • Innate Defenses: Surface barriers and internal innate defenses.

Page 2: Infectious Agents

• Types of Infectious Agents:

  • Bacteria: Unicellular prokaryotes.

  • Viruses: Nonliving infectious agents.

  • Fungi: Spores and multicellular organisms.

  • Protozoans: Complex, single-celled organisms.

  • Multicellular Parasites: Including tapeworms.

  • Prions: Infectious protein particles.

Page 3: Bacteria and Viruses

• Bacteria:

  • Structure: Single-celled prokaryotes without nucleus.

  • Reproduction: Binary fission.

• Viruses:

  • Description: Obligate intracellular parasites.

  • Structure: Outer capsid and inner nucleic acid (DNA or RNA).

  • Replication: Must replicate inside a host; can kill or alter host cell functions.

Page 4: Fungi and Protozoa

• Fungi:

  • Nutrient Acquisition: Decompose dead organic matter or parasitize.

  • Human Impact: Some cause disease through tissue invasion, allergens, or poisoning.

• Protozoans:

  • Complexity and Habitat: Most are harmless; can parasitize humans.

  • Examples: Trypanosomes associated with diseases like African sleeping sickness.

Page 5: Multicellular Parasites and Prions

• Multicellular Parasites:

  • Nematodes: E.g., hookworm infecting the gut.

  • Arthropods: E.g., ticks transmitting diseases.

• Prions:

  • Function: Cause degenerative diseases in the nervous system by misfolding normal proteins.

  • Example: Chronic Wasting Disease in deer and elk.

Page 6: The Immune System Basics

• Two Defense Systems:

  • Innate (Nonspecific) Defense System: First line of defense and innate immune response.

  • Adaptive (Specific) Defense System: Targets specific pathogens more effectively.

Page 7: Innate Immunity Components

• 1st Line of Defense: Surface Barriers

  • Skin and mucous membranes prevent pathogen entry.

• 2nd Line of Defense: Non-specific Internal Defenses

  • Comprises cells, chemicals, and physiological responses.

Page 8: Cells of Innate Immunity

• Main Cell Types:

  • Macrophages: Primary phagocytes, engulf pathogens.

  • Neutrophils: Become phagocytic when encountering pathogens.

  • Dendritic Cells: Present antigens to T cells after digesting pathogens.

  • Eosinophils: Target parasitic worms, weakly phagocytic.

Page 9: Phagocytosis Process

• Phagocytosis Mechanism:

  • Engulfment of microbe by endocytosis.

  • Breakdown by lysosome; removal of indigestible material by exocytosis.

Page 10: Opsonization

• Definition: Process that enhances phagocytosis.

• Mechanism:

  • Antibodies or complement component C3b bind to bacteria, facilitating recognition and binding by phagocytes.

Page 11: Natural Killer (NK) Cells

• Function:

  • Type of lymphocyte that targets cells not recognized as 'self'.

  • Induces apoptosis in infected/noxious cells by releasing perforin and granzymes.

Page 12: Basophils and Mast Cells

• Role in Inflammation:

  • Release inflammatory mediators (histamine, heparin, eicosanoids).

  • Histamine: Causes vasodilation and increases capillary permeability.

Page 13: Non-specific Internal Defenses

• Components:

  • Cellular and chemical components.

  • Antimicrobial Proteins: Directly attack microorganisms or inhibit reproduction.

    • Examples: Interferons and complement proteins.

Page 14: Interferon Function

• Interferons:

  • Secreted by virus-infected cells to protect neighboring cells.

  • Mechanisms: Block protein synthesis, degrade viral RNA, stimulate NK cells and macrophages.

Page 15: The Complement System

• Overview:

  • Comprised of at least 30 plasma proteins (e.g., C1-C9).

  • Activation leads to:

    • Inflammation amplification,

    • Pathogenic cell death through lysis,

    • Immune complex elimination.

Page 16: Further with Internal Defenses

• Non-specific Internal Defenses continued: Cells, Chemicals (e.g., antimicrobial proteins), and Physiological Responses.

Page 17: Fever Response

• Pyrogens: "Fire generators" that cause fever in response to infections.

  • Produced by leukocytes and macrophages upon exposure to pathogens.

Page 18: Inflammation Overview

• Localized Response:

  • Triggered by tissue injury from pathogens.

  • Process involves release of inflammatory and chemotactic factors, leading to vascular changes and immune cell recruitment.

Page 19: Symptoms of Inflammation

• Characteristics:

  • Redness and warmth due to increased blood flow.

  • Swelling due to capillary permeability increases.

  • Pain and loss of function from pressure and biochemical events.

Page 20: Benefits of Inflammation

• Purpose:

  • Dilutes toxins and limits use of affected area.

  • Antibodies permeate vessels; exudate proteins aid in defense and cleanup.

  • Promotes leukocytosis and immune cell migration.

Page 21: Inflammation Types

• Common Terminology:

  • Dermatitis: Inflammation of skin

  • Appendicitis: Inflammation of the appendix

  • Meningitis: Inflammation of the meninges

  • Suffix "itis" indicates inflammation.

Page 22: Quiz Question

• Which of the following act(s) as the first line of defense against foreign pathogens?

  • a) Skin

  • c) Mucous membranes

  • d) Both a and c

Page 23: Quiz Question

• Inflammatory chemicals act as:

  • b) vasodilators

Page 24: Quiz Question

• An increase in white blood cell number in the bloodstream, characteristic of inflammation, is called:

  • b) leukocytosis

Page 25: Quiz Question

• The process of attaching antibodies or complement proteins to the bacterial cell wall to enhance phagocytosis is called:

  • d) opsonization

Page 26: Quiz Question

• Response to release of pyrogens:

  • a) An increase in body temperature set point.