Immune System Vocabulary

The Immune System

Immune Response

• A target-specific system of defense.
• Primarily involves lymphocytes and lymphoid tissue.

Anatomy and Physiology

• The immune system comprises specialized white blood cells and lymphoid tissue.
• Maintains immunocompetence: the ability to protect a person from external invaders and the body’s altered cells.
• Function is supported by:
  • Natural killer cells
  • Antibodies
  • Nonantibody proteins (cytokines)

White Blood Cells (Leukocytes)

• Produced in bone marrow from stem cells.
• Types:
  • Lymphocytes
  • Neutrophils
  • Monocytes

Lymphocytes

• T-cell or B-cell lymphocytes.
• Primary participants in the immune response.
• Distinguish harmful substances and ignore the natural.

T-Cell Lymphocytes

• Manufactured in bone marrow and travel to the thymus gland.
• Mature to become either regulator T cells or effector T cells.
• Components:
  • Regulator T cells
    • Helper T cells
      • Important in fighting infection
      • T4 cells or CD4 cells
    • Suppressor T cells
      • Limit or turn off the immune response in absence of continued antigenic stimulation
  • Effector T cells
    • Killer (cytotoxic) cells

T-Cell Lymphocyte Components

• Antigens: protein markers on cells
• Antibodies: chemical substances that destroy foreign agents
  • Cytotoxic T cells
  • Lymphokines
• Cell-mediated response: T cells survey proteins, analyze surface features, and attack differing antigens.

B-Cell Lymphocytes

• Mature in bone marrow and migrate to the spleen and other lymphoid tissue.
• Components:
  • Plasma cells: produce antibodies; humoral response from antibody response
  • Memory cells: convert to plasma cells on re-exposure to specific antigen

Neutrophils and Monocytes

• Neutrophils—microphages
• Monocytes—macrophages
• Perform phagocytosis: engulfing and digesting bacteria and foreign material.

Neutrophils

• Phagocytes that perform phagocytosis.
• Also called microphages because they are small, present in blood, and migrate to tissue.

Monocytes

• Macrophages because they are large and present in tissues (lungs, liver, lymph nodes, spleen, peritoneum).
• Migrate after a cell-mediated response.

Lymphoid Tissues

• Play a role in the immune response and prevention of infection.
• Types:
  • Thymus gland: programs T lymphocytes to become regulator or effector T cells
  • Tonsils and adenoids: filter bacteria from tissue fluid
  • Spleen: emergency reservoir of blood and removes bacteria and old or damaged red blood cells from circulation
  • Lymph nodes: vessels that drain tissue fluid (lymph)

Question 1

Which of the following is the function of macrophages and neutrophils?
A) Phagocytosis
B) Antibody production
C) Complement system
D) Suppression of autoimmunity

Answer

A) Phagocytosis

Natural Killer (NK) Cells

• Lymphocyte-like cells that circulate looking for virus-infected and cancer cells.
• NK cells identify atypical markers on the membranes of these cells.
• Release potent chemicals that lethally alter the target cell’s membrane.
• Cancer cells can escape NK cell surveillance, causing them to spread.

Antibodies

• Proteins produced by B-lymphocyte plasma cells, also referred to as immunoglobulins (Igs).
• Five types: IgA, IgD, IgE, IgG, and IgM.
• Immunoglobulins bind with antigens.
• Promote the destruction of invading cells by hindering antigens physically:
  • Neutralizing their toxins
  • Linking them together (agglutination)
  • Causing them to precipitate or become solid

Nonantibody Proteins

• Provide additional methods for disabling antigens and further protecting the body.
• Types:
  • Complement system: activated in a chain reaction when an antibody binds with an antigen
  • Cytokines: chemical messengers released by lymphocytes, monocytes, and macrophages
• Opsonization: proteins cooperate with antibodies to attract phagocytes, coat antigen to make them more recognizable for phagocytosis

Interleukins

• Carry messages between leukocytes and tissues that form blood cells.
• Examples:
  • Inflammation and fever
  • Scar tissue by fibroblasts
  • Growth and activation of NK cells and additional T cells
  • Mast cells

Interferons

• Chemicals that primarily protect cells from viral invasion.
• Enable cells to resist viral infection and slow viral replication.

Tumor Necrosis Factor (TNF)

• Type of cytokine.
• Helps in cellular repair when administered in small doses.

Question 2

Immunity to a disease after recovery is possible because the first exposure to the pathogen has stimulated the formation of which of the following?
A) Antigens
B) Memory cells
C) Complement
D) Natural killer cells

Answer

B) Memory cells

Types of Immunity

• Naturally acquired active immunity: occurs as a direct result of infection by a specific microorganism
  • Example: measles
• Artificially acquired active immunity: results from administration of a killed or weakened microorganism or toxoid
  • Example: influenza
• Passive immunity: ready-made antibodies are given to a susceptible person
  • Example: newborns receiving antibodies from their mothers

Question 3

A baby is born temporarily immune to the diseases to which the mother is immune. The nurse understands that this is an example of which type of immunity?
A) Naturally acquired passive immunity
B) Artificially acquired passive immunity
C) Naturally acquired active immunity
D) Artificially acquired active immunity

Answer

A) Naturally acquired passive immunity

Assessment

• History of immunizations, recent and past infectious diseases, recent exposure to infectious diseases, drug history, allergy history
• Physical Examination:
  • General appearance (healthy, ill, malnourished, tired)
  • Skin examination for rashes or lesions
  • Abdominal assessment for enlarged liver or spleen
  • Inspection of pharynx for large, red tonsils and drainage

Diagnostic Tests

• Laboratory tests: complete blood count with differential
• Protein electrophoresis screens: diseases associated with deficiency or excess immunoglobulins
• T-cell and B-cell assays: enzyme-linked immunosorbent assay
• Skin tests: disease-specific antigens
• Anergy: inability to mount an immune response (common with AIDS or immunosuppression)

Nursing Management

• Identify allergic substances; hypersensitivity
• Explain diagnostic skin testing procedures
• Use standard precautions
• Follow agency guidelines for controlling infectious diseases or protecting client who is immunosuppressed