Introduction to the Immune Response and Inflammation

Introduction to the Immune Response and Inflammation

Body’s Defenses

• Barrier defenses
• Cellular defenses
• Inflammatory response
• Immune response

Barrier Defenses

• Skin
  • Protects the internal tissues and organs of the body
• Mucous membrane
  • Lines the areas of the body that are exposed to external influences but do not have skin protection
• Gastric acid
  • Secreted by the stomach in response to many stimuli
• Major histocompatibility complex
  • Distinguishes between self-cells and foreign cells

Types of Cellular Defenses

• Mononuclear phagocyte system (MPS)
  • Composed of:
    • Thymus gland
    • Lymphatic tissue
    • Leukocytes
    • Lymphocytes
    • Numerous chemical mediators

Types of White Blood Cells—Leukocytes—Produced by the Body

 

 

Types of Leukocytes

 

 

The Inflammatory Response Hageman Factor (Factor XII)

• A chemical in the plasma activated by cell injury
• Responsible for activating three systems in the body
  • The kinin system
  • The clotting cascade: starts blood clotting
  • The plasminogen system: starts the dissolution of blood clots

The Role of Bradykinin

• Causes local vasodilation
• Stimulates nerve endings to cause pain
• Causes the release of arachidonic acid
• This release of arachidonic acid causes the release of autocoids

Types of Autocoids Released

• Prostaglandins
  • Some augment the inflammatory reaction and some block it
• Leukotrienes
  • Some can cause vasodilation and increased capillary permeability and some can block the reactions
• Thromboxanes
  • Cause local vasoconstriction and facilitate platelet aggregation and blood coagulation

Clinical Presentation

• Calor (heat)
  • Caused by increased blood flow
• Tumor (swelling)
  • Caused by fluid that leaks into the tissues
• Rubor (redness)
  • Caused by the increase in blood flow due to vasodilation
• Dolor (pain)
  • Caused by the activation of pain fibers

Inflammatory Response

 

 

Immune Response

• Specific invasions stimulate specific responses through the immune system
  • Lymphocytes produced in the bone marrow can develop into T lymphocytes or B lymphocytes
  • Other identified lymphocytes include natural killer cells and lymphokine-activated killer cells
    • These cells are aggressive against neoplastic or cancer cells and promote rapid cellular death

Types of T Cells

• Effector or cytotoxic T cells
• Helper T cells
• Suppressor T cells

Function of T Cells

• Effector or cytotoxic T cells
  • Found throughout the body
  • Aggressive against non-self cells
  • Can directly destroy foreign cells or mark cell so other cells can destroy them
• Helper T cells
  • Stimulate the activity of B cells and effector T cells
• Suppressor T cells
  • Monitor the chemical activity in the body
  • Act to suppress B-cell and T-cell activity when the foreign antigen is under control

Cell-Mediated Response

 

 

The Role of the B Cell

• Programmed to identify specific proteins or antigens
• Involved in humoral immunity
• Produces antibodies or immunoglobulins

Humoral Immune Response

 

 

Response to the Varicella Virus

 

 

Other Mediators in the Immune Response

• •nterferons
  • Prevent viral replication and suppress malignant cell replication and tumor growth
• Interleukins
  • Chemicals secreted by active leukocytes to influence other leukocytes
• Tumor necrosis factor (TNF)
  • Chemical released by macrophages; inhibits tumor growth and can cause tumor regression

Conditions That Cause Problems Involving the Immune System

• Neoplasm
• Viral invasion
• Autoimmune disease
• Transplant rejection

Theories of Autoimmune Disease

• Result of response to a cell that was invaded by a virus, leading to antibody production to similar cells
• In a state of immunosuppression, the suppressor T cells do not suppress autoantibody production
• There is a genetic predisposition to develop autoantibodies