Innate and Adaptive Immunity

Immunity Overview

• Types of Immunity

  • Innate Immunity: Natural barriers

  • Adaptive Immunity (Acquired)

• Lines of Defense:

  • First Line: Natural barriers

    • Physical, mechanical, and biochemical barriers

  • Second Line: Inflammatory response

  • Third Line: Adaptive immunity

First Line of Defense

• Physical and Mechanical Barriers:

  • Skin, low temperature/pH

  • Gastrointestinal, genitourinary, respiratory tracts

  • Sloughing of cells, coughing, sneezing, washing, urinary actions, and mucus/cilia

• Biochemical Barriers:

  • Secretions in mucus, sweat, saliva, tears, earwax

  • Antibacterial peptides: cathelicidins, defensins

  • Normal microbiome inhibits pathogens (e.g., Lactobacillus, ammonia, phenols)

Second Line of Defense

• Inflammatory Response:

  • Triggered by infection, damage, ischemia, nutrient deprivation, and heat extremes

  • Nonspecific, rapidly initiated without memory cells

  • Cardinal Signs: Redness, heat, swelling, pain, loss of function

  • Vascular Response:

    • Dilation and increased permeability of blood vessels, white blood cells adhere and migrate

• Local Manifestations of Inflammation:

  • Functions include diluting toxins, carrying leukocytes to injury site, and clearing debris

Types of Exudate

• Exudate: Fluid and cells (e.g., proteins, debris)

  • Serous: Watery, early inflammation

  • Fibrinous: Thick, indicates advanced inflammation

  • Purulent: Pus indicating bacterial infection

  • Hemorrhagic: Contains blood

Systemic Manifestations of Inflammation

• Fever: Results from pyrogens affecting the hypothalamus

• Leukocytosis: Increased leukocyte count, especially immature cells

• Acute-Phase Reactants: Increased plasma protein synthesis

Chronic Inflammation

• Definition: Lasts longer than 2 weeks, often due to unsuccessful acute response

• Characteristics:

  • Dense lymphocyte and macrophage infiltration

  • Granuloma and giant cell formation

Wound Healing

• Three phases:

  • Phase I: Hemostasis (Coagulation)

  • Phase II: Inflammation: Neutrophils and macrophages clean the wound

  • Phase III: Proliferation: Healing and tissue formation begins

  • Phase IV: Remodeling and maturation of scar tissue

• Types of Healing:

  • Primary Intention: Minimal tissue loss, restores original structure

  • Secondary Intention: More tissue replacement, scars form

Dysfunctional Wound Healing

• Causes include ischemia, infection, excessive scar formation, malnutrition, and medications

• Characteristics:

  • Dehiscence: Wound pulling apart at suture line

  • Contractures: Excessive contraction leading to tension

Aging and Immunity

• Impairments in Older Adults:

  • Delayed inflammation, increased infections due to weakened immune function

Adaptive Immunity Characteristics

• Components: T and B lymphocytes, antibodies, long-term protection, slower but specific response

• Functional Interaction:

  • Humoral immunity (B cells) and Cellular immunity (T cells)

  • Memory cells respond faster upon subsequent exposures

Antigens and Antibodies

• Antigen: Triggers an immune response, can be proteins, pathogens, or vaccines

• Antibody Classes: IgG, IgA, IgM, IgE, IgD—varying functions in immunity

Immune Responses**:

• Primary Immune Response: Slower, involves memory cell generation

• Secondary Immune Response: Faster, larger antibody production due to memory cells

Types of Immunity

• Active Immunity: Long-lived, from natural exposure or vaccination

• Passive Immunity: Short-lived, transferred antibodies from donor to recipient.