Immunology and Vaccines

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CHAPTER 24 Immunology and Vaccines

I. Introduction: The immune system consists of physical and chemical barriers and specific and nonspecific mechanisms to eliminate antigens.
II. Components of the Immune System

A. Antigen-presenting cells

1. B cells

a. Produce antibodies

2. Monocytes

a. Precursor cell to macrophages
b. Circulate in blood; migrate into tissues
c. Scavenge foreign cells

3. Macrophages

a. Phagocytose and kill microorganisms; activation of T cells and initiation of immune response
b. Secrete cytokines
c. Present antigens to lymphocytes

4. Dendritic cells

a. Activation of T cells and initiation of adaptive immune response
b. Star-shaped

B. Polymorphonuclear leukocytes or neutrophils (PML or PMN)

1. Neutrophils

a. Phagocytose and kill microorganisms; first line of defense
b. Most abundant (40%–70% of white blood cells [WBC])
c. Effector cells of innate immunity
d. Short-lived (half-life of mature neutrophils is 2–3 days)

2. Eosinophils

a. Kill antibody-coated parasites through release of toxic substances, major basic protein, eosinophil cationic protein, and several enzymes
b. ~5% of WBC
c. Protects against parasitic organisms
d. Major source of inflammatory mediators
e. Bind IgE

3. Basophils

a. Rare (<5% of WBC)
b. Unknown function
c. Bind to IgE
d. Source of type I hypersensitivity reactions

4. Mast cells

a. Function: expulsion of parasites from body through release of granules containing histamine and other active agents
b. Occur in different body tissues
c. Generate protective acute inflammatory response
d. Source of type I hypersensitivity reactions
e. Degranulation, major contributor to inflammation and allergies

C. Cytotoxic leukocytes

1. Natural killer cells

a. Kills cells infected with certain viruses
b. Larger than lymphocyte with granular cytoplasm
c. Effector cell of innate immunity

2. Lymphokine-activated killers (LAK)

a. Kill various tumor target cells and abnormal lymphocytes

D. Lymphocytes

1. B cells: produce antibodies
2. T cells: helper, cytotoxic

a. Helper T cells: regulate immune response
b. Cytotoxic T cells: kill altered cells (infected with viruses, tumor cells)

E. Antibodies

1. Ig (immunoglobulin) G: most common antibody in blood

(1) Active in blood against bacteria and viruses
(2) Helps phagocytes eliminate antigens

2. IgM: reacts with certain antigens; found in circulating body fluids
3. IgA: plays a role in mucosal immunity
4. IgD: found on B cells. not released from the cell

a. May be involved in B-cell activation

5. IgE: involved in allergic reactions; stick to mast cells and release inflammatory substances

a. Rare in blood

F. Acute phase reactants

1. Soluble mediators of the immune system
2. Levels increase if infection or tissue damage is present
3. Control tissue injury; increase host resistance to infection; promote tissue repair

G. Cytokines

1. Interferons (IFN): important in controlling viral infections and augmenting immune response

a. Nonspecific immune system
b. Examples: INF-α, INF-β, Interferon-γ

2. Tumor necrosis factors (TNF): produced by macrophages and T lymphocytes; regulate immune response and hematopoiesis

a. Examples: TNF-α, TNF-β

3. Interleukins (IL): mediators between leukocytes

a. Examples: IL-1, IL-2, IL-3, IL-4

4. Chemokines: directed migration of leukocytes during immune response
5. Transforming growth factor (TGF): involved in stem cell differentiation and other functions
6. Hematopoietic colony-stimulating factors (CSF): important in maturation of leukocytes

H. Active and passive immunity

1. Active immunity

a. Response to an infection
b. Immunization (vaccination)

2. Passive immunity

a. Mother-to-baby

(1) IgG crosses placenta
(2) IgA in breast milk

b. Antibody injection into nonimmune person (antiserum)

I. Innate versus adaptive defense system

1. Nonspecific defense mechanism (innate)

a. First line of defense: physical barriers (skin, mucosa)
b. Second line of defense: chemical barriers (phagocytes, natural killer cells, inflammation, fever, antimicrobial proteins)

2. Specific defense mechanisms (adaptive)

a. Third line of defense: immune system (lymphocytes, antibodies)

(1) Protects against infectious agents and abnormal cells
(2) Responsible for most complement activation

J. Antigens

1. Substance from a pathogen or foreign organism capable of inducing a specific immune response
2. When the body is exposed to an antigen for the first time, antibody production is slow and at low levels. If the body is exposed to the same antigen again, the antibody response is more intense and rapid.

III. Immunization/Vaccinations

A. Basic Principles of Vaccination

1. Exposure to antigen will provoke an immune response.
2. Repeated exposure to antigen produces immunological memory.
3. Vaccine strategy: make a vaccine that gives a strong immune response—safely
4. US Centers for Disease Control publish recommended vaccination schedules

B. Common Vaccines (Figures 24-1 and 24-2)

1. Diphtheria, tetanus, pertussis (DTaP, DT, Rd, Tdap) vaccines

a. Daptacel (DTaP) diphtheria, tetanus toxioids, and acellular pertussis

(1) Indicated for infants and children, 6 weeks to 6 years old
(2) Dose is IM injection of 0.5 mL given at 2, 4, 6, and 15–20 months; booster at 4–6 years (total of 5 doses)
(3) How supplied: 0.5 mL suspension for injection
(4) Adverse effects: fever, pain and swelling at injection site, irritability, loss of appetite, drowsiness

b. Pediarix (DTaP-HBV-IPV) diphtheria, tetanus toxoids, and acellular pertussis, hepatitis B (recombinant), inactivated poliovirus vaccine

(1) Indicated for infants and children, 6 weeks to 7 years old
(2) Dose is IM injection of 3 doses of 0.5 mL each, at 6- to 8-week intervals; first dose at minimum age of 6 weeks; not used for booster doses
(3) How supplied: 0.5 mL vial
(4) Adverse effects: fever, pain and swelling at injection site, irritability, loss of appetite
(5) Diphtheria toxoid, tetanus toxoid, and pertussis antigens are the same as Infanrix

c. Infanrix (DTaP; diphtheria, tetanus toxoids, and acellular pertussis)

(1) Indicated for infants and children, 6 weeks to 7 years old
(2) Dose is IM injection of 0.5 mL each at 2, 4, and 6 months; one booster at 15–20 months and another booster at 4–6 years of age (total of 5 doses)
(3) How supplied: 0.5 mL vial
(4) Adverse effects: fever, pain and swelling at injection site, irritability, loss of appetite, drowsiness
(5) Note: Diphtheria toxoid, tetanus toxoid, and pertussis antigens are the same as Pediarix and may be used to complete DTaP immunization with Pediarix.

d. Adacel (Tdap) tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis

(1) Indicated for ages 11–64 years old as an active booster immunization (single-dose)
(2) Dose is IM injection of one dose of 0.5 mL; 5 years should pass since the last tetanus, diphtheria, or pertussis vaccine
(3) How supplied: 0.5 mL vial
(4) Adverse effects: fever, pain and swelling at injection site, headache, rash

e. Boostrix (Tdap) tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis

(1) Approved for ages 10–64 years old as an active booster immunization (single-dose)
(2) Dose is IM injection of one dose of 0.5 mL; 5 years should have passed since the last tetanus, diphtheria, or pertussis vaccine
(3) How supplied: 0.5 mL vial
(4) Adverse effects: fever, pain and swelling at injection site, gastrointestinal upset, headache

2. Haemophilus influenzae vaccines

a. Combivax (Haemophilus b conjugate [meningococcal protein conjugate]) and hepatitis B [recombinant] vaccine)

(1) Indicated for infants 6 weeks to 15 months for Haemophilus influenzae type b and hepatitis B virus (HBsAg-negative mothers)
(2) Dose is IM injection at 2, 4, and 12–15 months (total of 3 doses)

(a) For best response, the interval between the second and third dose should be 8–11 weeks.

(3) How supplied: 0.5 mL vial
(4) Adverse effects: pain and swelling at injection site, fever, erythema, somnolence, rash, diarrhea, anorexia
(5) Note: May be administered concurrently with DTP, OPV, eIPV, Varivax, M-M-R II, and booster of DTaP

b. Pedvax HIB (Haemophilus b conjugate vaccine [meningococcal protein conjugate])

(1) Indicated for children 2–71 months for Haemophilus influenzae type b
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