Immunity, Inflammation, and Infection

Physical and Chemical Barriers to Infection

The First Line of Defense: The body's primary protection against external threats consists of physical and chemical barriers.
- Skin: Acts as a physical shield against invading organisms.
- Mucous Membranes: Provide a physical and chemical barrier in various body systems.
The Second Line of Defense: If the first line is breached, the body employs two specific processes:
- Phagocytosis: The process by which specific cells ingest and destroy foreign material.
- Inflammation: A non-specific response to tissue injury.

Fundamental Concepts of Immunity

Resistance: Immunity provides resistance to invading organisms, allowing the body to fight off invaders once they have gained access.
Antigen: Any substance that the body perceives as foreign and that triggers an immune response.
Antibodies: Proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses.
Innate (Natural) Immunity: Present at birth. It includes physical and chemical barriers to invasion as well as substances that protect and repair tissues and stimulate the body to fight off disease.
- Innate immunity is considered a non-specific defense against infection.
- Key components include physical/chemical barriers, inflammation, and phagocytosis.
Acquired Immunity: Immunity that develops after exposure to a specific pathogen or through vaccination.

Organs and Components of the Immune System

Leukocytes (White Blood Cells): The primary cellular components of the immune system.
- Leukocytes are described as colorless cells.
- They are capable of phagocytosis, which is the ingestion of bacteria that cause infection upon invasion.
Thymus and Bone Marrow: Central organs for the production and maturation of immune cells.
Lymph Nodes: Small structures that filter foreign particles and house lymphocytes.
Spleen: Filters the blood and helps fight certain kinds of bacteria.
Liver: Plays a role in immunity through the production of proteins and the action of specialized macrophages.

The Inflammatory Process

Definition: A series of cellular changes that signal the body’s response to injury or infection. The word literally translates to ‘‘the fire within.’’
Causes: Inflammation may be triggered by:
- Physical agents.
- Chemical stimuli.
- Biologic agents.
Actions in the Inflammatory Process:
- Hemodynamic Changes: Alterations in blood flow.
- Increased Capillary Permeability: Allows fluids and cells to move from the blood into the tissues.
Chemical Mediators: Hemodynamic changes and vascular permeability occur with the assistance of several mediators:
- Prostaglandins.
- Histamine.
- Leukotrienes.
- Cytokines.
- Eicosanoids.
Kinin System:
- Produces bradykinin, which mediates blood vessel dilation and permeability.
- Bradykinin is specifically responsible for producing pain, which is a classic sign of inflammation.
Complement System: This system is particularly important in immunologically mediated reactions involving antigen-antibody complexes.

Anti-inflammatory Mechanisms

Cortisol: A hormone produced by the adrenal cortex.
- Acts as an anti-inflammatory substance.
- Slows the release of histamine.
- Stabilizes lysosomal membranes.
- Prevents the influx of leukocytes.
- Result: Cortisol impedes the inflammatory process and protects the body from excessive or prolonged inflammation.
- Pharmacology: Medications like corticosteroids are designed to mimic the actions of cortisol and are used to treat various inflammatory conditions.

Signs and Symptoms of Inflammation

Local Inflammation: Characterized by the four classic manifestations, which result in a fifth clinical outcome:
1. Heat.
2. Swelling.
3. Redness.
4. Pain.
5. Loss of function.
Systemic Inflammation: Responses that affect the entire body, including:
- Fever.
- Headache.
- Muscle aches.
- Chills.
- Sweating.
- Leukocytosis: An increase in the number of white blood cells.

Wound Healing and Repair

Tissue Repair and Regeneration: These processes are set in motion from the very beginning of the inflammatory process.
Factors Influencing Speed: The rate of healing depends on:
- The type of tissue injured.
- The severity of the wound.
- The presence of infection.
- The general health of the host.

The Nature of Infection

Definition: Infection involves the invasion of the body by microorganisms, the multiplication of those invading organisms, and the resulting tissue damage.
Infection vs. Inflammation:
- Inflammation is a non-specific body reaction to tissue injury.
- Infection is a specific process that causes tissue injury.
- Infection always results in inflammation, but inflammation may be caused by processes other than infection.
- Inflammation precedes infection.
Infectious Agents: Infection is caused by a wide variety of microorganisms:
- Bacteria: One-celled microorganisms capable of multiplying rapidly; classified by shape, cluster pattern, oxygen requirements, and staining ability.
- Viruses.
- Fungi.
- Protozoa.
- Rickettsiae.
- Helminths.
- Mycoplasmas.

Transmission of Infection: The Chain of Infection

Infection only occurs when these factors occur in a specific sequence:

Causative Agent: The pathogen responsible for the disease.
Reservoir: Where the pathogen lives and grows.
Portal of Exit: The way the pathogen leaves the reservoir.
Mode of Transfer: Method by which the agent moves to a new host.
Portal of Entry: The way the pathogen enters the susceptible host.
Susceptible Host: An individual capable of being infected by the agent.

Nursing Care and Treatment for Infections

Patient Education and Nutrition:
- Urge patients to consume adequate fluids.
- Encourage a high-protein, high-vitamin diet.
Interventions:
- Maintain isolation if required.
- Conduct necessary laboratory tests.
- Administer antibiotic drug therapy.
- Utilize hyperbaric oxygen therapy where appropriate.

Medical and Surgical Asepsis

Medical Asepsis (Clean Technique):
- Goal: Limit the spread of microorganisms.
- Handwashing: Identified as the most effective method to prevent cross-contamination.
Surgical Asepsis (Sterile Technique):
- Goal: Eliminate microorganisms from any object that comes into contact with the patient.
- Includes techniques to prevent non-sterile surfaces from contacting the patient (e.g., during dressing changes).

Centers for Disease Control (CDC) Precautions

Standard Precautions:
- Infection control guidelines from HICPAC and the CDC.
- Applied to all patients regardless of isolation status.
- Used during contact with blood, bodily fluids, secretions (excluding sweat), excretions, broken skin, and mucous membranes.
- Used when handling materials soiled or contaminated with bodily fluids.
Transmission-Based (Isolation) Precautions:
- Airborne Precautions.
- Droplet Precautions.
- Contact Precautions.
Protective Equipment (PPE):
- Gloves.
- Isolation gowns.
- Face protection.
- Respiratory protection.
Protective Environment Standards:
- HEPA filtration.
- Directed room air flow.
- Positive pressure.
- Sealed environment.
- Easily cleanable surfaces.

Specialized Topics: Bioterrorism and Immunocompromised Patients

Bioterrorism: The intentional use of microorganisms (viruses, bacteria, toxins) to cause death or disease.
- Dissemination methods include powders, aerosols, or contamination of food and water.
Immunocompromised Patients: Individuals with decreased immunity to infection.
- Includes patients receiving chemotherapy and those with low white blood cell counts.
- These patients are at increased risk for bacterial, fungal, parasitic, and viral infections.

Specific Immune Defenses and Hypersensitivity

Immune Response Pathways:
- Antibody-mediated (Humoral) Immunity.
- Cell-mediated Immunity.
Hypersensitivity and Allergy:
- Triggered by Allergens: Examples include house dust, pollen, molds, animal dander, insect venom, pharmacologic agents, smoke, and feathers.
- Medical Treatment: Priority must be given to the care of the airway.
- Nursing Care: Document all allergies, symptoms, and treatments.
Anaphylaxis:
- Most common cause is the use of antimicrobials, specifically penicillin.
- S.A.F.E. Action Guide:
  1. S: Seek immediate medical help.
  2. A: Identify the Allergen.
  3. F: Follow up with a specialist.
  4. E: Carry Epinephrine for emergencies.
- Medical Treatment: Oxygen, IV epinephrine, dopamine, nebulizer treatments, diphenhydramine, and corticosteroids.

Autoimmune Diseases

Cause: Natural or self-tolerance is disrupted, causing the immune system to destroy its own tissues.
Medical Treatment: Often involves corticosteroids.
Nursing Care:
- Ensure adequate rest.
- Maintain hydration and nutrition.
- Focus on the prevention of infection.

Questions and Discussion

Question 1: The inflammatory process involves four changes or factors: hemodynamic changes, increased permeability of membranes, chemical mediators, and ______________.
- A. hormonal factors
- B. endocrine changes
- C. constriction of the capillary bed
- D. decreased release of histamine
- Answer: [Note: Based on the provided slide context regarding mediators like kinins and hemodynamic changes, the expected answer involves identifying the missing standard component of the process. In typical pathophysiology, the fourth component often refers to the cellular response/leukocyte emigration, though the slide structure highlights hemodynamic, permeability, and mediators.]
Question 2: ____________ are one-celled microorganisms capable of multiplying rapidly within a susceptible host. They are classified by shape, cluster pattern, whether they need oxygen, and their ability to take up and retain stains.
- A. Fungi
- B. Bacteria
- C. Viruses
- D. Protozoa
- Answer: B. Bacteria