Immune System Study Notes

Immunity

Definition

  • Immunity is the body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells.

Types of Immunity

  • Innate (nonspecific) immunity
  • Adaptive (specific) immunity

Differences Between Specific and Nonspecific Immune Responses

Nonspecific (Innate) Immunity

  • Present at birth
  • Responds quickly
  • Not antigen-specific
  • Examples: Skin, fever, inflammation

Specific (Adaptive) Immunity

  • Develops after exposure
  • Slower response
  • Antigen-specific
  • Examples: T cells and B cells

Lines of Defense

First Line of Defense

  • Skin
  • Mucous membranes
  • Secretions (tears, saliva)

Second Line of Defense

  • Phagocytes
  • Natural killer cells
  • Inflammation
  • Fever
  • Antimicrobial proteins (like complement)

Third Line of Defense

  • B and T lymphocytes
  • Antibodies

Inflammation

Definition

  • Localized tissue response to injury or infection.
  • Involves swelling, redness, heat, and pain.

Functions of the Inflammatory Response

  • Prevent spread of damaging agents
  • Remove pathogens and dead cells
  • Begin tissue repair

Causes of Redness and Heat

  • Due to local hyperemia caused by vasodilation (increased blood flow to the area)

Fever

Definition

  • A systemic response to infection.
  • Body temperature rises due to pyrogens (released by leukocytes/macrophages) affecting the hypothalamus.

Complement

Definition

  • A group of plasma proteins that enhance the immune response.
  • Examples: promote cell lysis, inflammation, and phagocytosis.

Adaptive Defense

Definition

  • Specific immunity that targets particular pathogens.

Two Parts

  • Humoral immunity (B cells, antibodies)
  • Cell-mediated immunity (T cells)

Immunocompetence

Definition

  • The ability of lymphocytes to recognize a specific antigen by binding to it.

Antibody Production

  • B lymphocytes (plasma cells)

Antibodies

Definition

  • Y-shaped proteins that bind antigens.

Structure

  • 2 heavy chains
  • 2 light chains
  • Variable (antigen-binding) regions
  • Constant regions

T and B Lymphocytes

B Cells

  • Mature in bone marrow
  • Involved in humoral immunity
  • Produce antibodies

T Cells

  • Mature in thymus
  • Involved in cell-mediated immunity
  • Do not produce antibodies

Humoral Immunity

Active Humoral Immunity

  • Body produces antibodies

Passive Humoral Immunity

  • Antibodies are received

Types of Active and Passive Immunity

Active Natural

  • Infection

Active Artificial

  • Vaccination

Passive Natural

  • Antibodies from mother (placenta/breast milk)

Passive Artificial

  • Injection of antibodies (e.g., antivenom)

Defensive Mechanisms Used by Antibodies

  • Neutralization
  • Agglutination
  • Precipitation
  • Complement activation

Primary vs. Secondary Immune Responses

Primary

  • First exposure
  • Slower
  • Less antibody production

Secondary

  • Faster
  • Stronger due to memory cells

Cell-Mediated Immunity

Definition

  • Immunity involving T cells that target infected or abnormal cells directly.

Major Types of Cells in Cell-Mediated Immunity

  • Helper T cells (CD4+)
  • Cytotoxic T cells (CD8+)
  • Regulatory T cells

Autoimmune Disease

Definition

  • When the immune system attacks the body's own tissues.

Examples

  • Rheumatoid arthritis
  • Lupus
  • Multiple sclerosis
  • Type 1 diabetes

Organ Transplants

Autograft

  • From the same person

Isograft

  • From identical twin

Allograft

  • From another human

Xenograft

  • From another species

Immunodeficiency

Definition

  • Condition where the immune response is absent or weak.

Examples

  • SCID (Severe Combined Immunodeficiency)
  • AIDS (Acquired Immunodeficiency Syndrome)