Exam 3 Review

Types of Relationships Among Organisms

  • Parasitism

    • Definition: One individual benefits at the expense of another.

    • Example: A pathogen infecting a host, causing disease without harming itself.

  • Mutualism

    • Definition: Both organisms benefit from the relationship.

    • Example:

    • Bacteria in human intestines produce vitamins B and K while receiving a habitat.

    • Fungus and grass in the American Southwest; fungus protects grass from herbivores while gaining a habitat.

  • Commensalism

    • Definition: One organism benefits while the other is unaffected.

    • Examples:

    • Staphylococcus aureus enables Haemophilus influenza to grow on blood agar after being previously inoculated.

    • E. coli in intestines can remove oxygen, aiding anaerobic bacteria while not benefiting itself.

Important Definitions

  • Signs vs. Symptoms

    • Symptoms: Subjective effects of disease (e.g., nausea) perceived by the patient.

    • Signs: Objective indicators measurable by a doctor (e.g., vomiting).

  • Primary vs. Opportunistic Pathogen

    • Primary Pathogen: Causes disease in healthy individuals (can cause disease at any time).

    • Opportunistic Pathogen: Causes disease primarily in individuals with compromised immune systems.

Koch's Postulates

  • Four tenets to identify the cause of a disease:

    1. Microorganism must be present in every case of the disease.

    2. Microorganism must be grown in pure culture from diseased host.

    3. Pure culture must cause the disease when introduced to a healthy host.

    4. Microorganism must be isolated from the experimentally infected host.

Pathogen Adhesion

  • Adhesins: Protein-carbohydrate moieties allowing pathogens to attach to host cells.

  • Mechanisms of overcoming host defenses:

    • IgA antibodies blocked by new pili or IgA protease enzymes.

    • Endogenic Variation: Pathogens changing shapes to evade immune responses.

    • Mimicking Host Cells: Utilizing sialic acid/hyaluronic acid to confuse immune system.

Phagocytosis Overview

  • C5a: Chemotactic agent directing phagocytes.

  • C3b: Coats pathogens (opsonization) and binds to macrophages for easier engulfment.

  • Strategies bacteria use against phagocytosis:

    • C5a peptidase destroys C5a, hindering macrophage attraction.

    • Cytolytic toxins damage macrophages.

    • Capsules impede C3b binding.

    • Bacteria may bind antibodies incorrectly, preventing neutralization.

Immune Responses Overview

  • Complement Cascade System Activation: Activated via antigen-antibody complexes, leading to:

    • Establishment of inflammation.

    • Formation of Membrane Attack Complexes (MACs).

    • Opsonization of pathogens.

  • Phagocytes:

    • Macrophages: Long-living, present in tissues, first line of defense.

    • Neutrophils: Short-lived, strong, recruited from blood to tissues.

Cytokines Functionality

  • Communication molecules in the immune system (short-lived).

  • Key types discussed:

    • Chemokines: Direct immune cell movement.

    • Colony Stimulating Factors: Induce cell division.

    • Interferon: Protects against viral infections.

    • Interleukins: Facilitate inflammation and adaptive immunity.

    • Tumor Necrosis Factor (TNF): Promotes apoptosis (programmed cell death).

    • Pyrogens: Induce fever.

Innate Immune System Components

  • Natural Defenses:

    • Lysozyme: Degrades bacterial cell walls.

    • Peroxidase: Produces hypochlorite as a defense.

    • Lactoferrin & Transferrin: Iron-binding proteins to limit bacterial growth.

    • Defensins: Poke holes in bacterial membranes.

T Cells and Immune Cell Activation

  • T Helper Cells: Activate B cells and macrophages via cytokines.

  • T Cytotoxic Cells: Kill infected or defective cells through apoptosis and cytotoxic factors (perforins).

Adaptive Immunity Insights

  • Antigens: Substances that induce antibody production.

  • Epitopes: Specific parts of antigens recognized by antibodies.

  • Antibody Structure: Consists of heavy and light chains; has variable regions for binding epitopes.

  • Types of Antibodies: IgG, IgM, IgA, IgD, and IgE; know their primary functions.

    • IgG: Longest-lived, involved in secondary immune response.

    • IgM: Largest, important for blood infections.

    • IgE: Mediates allergic reactions and responses against parasites.

Vaccination Insights

  • Active vs. Passive Immunity: Active (body produces antibodies); Passive (antibodies given).

  • Natural vs. Artificial: Natural (natural exposure); Artificial (immunization).

  • Vaccine Types: Attenuated (weakened pathogen) vs. inactivated (dead pathogen).

  • Polio Vaccine Differences:

    • Salk Vaccine: Inactivated, requires injections.

    • Sabin Vaccine: Attenuated, oral administration, potential risk of causing disease.

Allergic Reactions and Hypersensitivities

  • IgE Mediated Allergies: Immediate responses; treatments include antihistamines and adrenaline for anaphylaxis.

  • Cytotoxic Allergies: Blood type reactions; specificity in anti-body presence (e.g., blood type A has B antibodies).

  • Delayed Cell Mediated Allergies: T-cell mediated reactions (e.g., poison ivy, TB test).

Autoimmune and Immunodeficiency Disorders

  • Autoimmune Disorders: Conditions where the immune system attacks self (e.g., Graves' disease, Type 1 diabetes, rheumatoid arthritis).

  • Primary Immunodeficiencies: Genetic defects (e.g., agammaglobulinemia).

  • Secondary Immunodeficiencies: Acquired through environment (e.g., malnutrition, AIDS).

Conclusion

  • Exam Tips: Understand definitions, examples, and differences in key concepts. Focus on types of relationships, immunity mechanisms, and sensitivity responses.

  • Total of 50 questions covering various aspects of microbiology and immunology, review all topics for a comprehensive understanding.