1. Chapter 22
Immunity and Serology

2. 22.1 Immunity to Disease Can Be Generated Naturally or Artificially
Adaptive immunity can result by actively producing antibodies to an antigen.
Active immunity occurs when the body’s immune system responds to antigens by producing antibodies and lymphocytes.
Naturally acquired active immunity follows illness or pathogen exposure.
Figure 22.02A: Naturally Acquired Active Immunity.

3. Figure 22.02B: Artificially Acquired Active Immunity.
Artificially acquired active immunity occurs through vaccination.
Vaccines contain treated or altered microbes, toxins, or parts of microbes.
A primary immune response occurs.
Memory cells are formed.
The person does not usually become ill.
Figure 22.02B: Artificially Acquired Active Immunity.

4. Figure 22.01AB: Effect of Vaccination on Disease Prevalence.
Vaccines are substances that prepare the immune system to recognize and respond to a pathogen and provide immunity
Data from the CDC, Summary of Notifiable Diseases, U.S., 2009.
Reproduced from The Amer. Acad. Microbiol., Adult Vaccines: A Grown Up Thing to Do
Figure 22.01AB: Effect of Vaccination on Disease Prevalence.

5. Whole agent vaccines contain weakened or inactivated antigens
Live, attenuated vaccines contain weakened microbes that multiply at only low levels, inducing a strong immune response
May provide lifelong immunity
Organisms can revert to a virulent form and cause disease
May affect those not inoculated nearby. ex) Sabin oral polio vaccine
should not be given to immunocompromised
A single-dose vaccine can combine vaccines for different diseases,
ex) MMR

6. Toxoid vaccines contain inactivated toxins with formalin
Inactivated vaccines contain killed pathogens, which induce a weaker immune response.
Booster shots are required to maintain immunity. ex) Salk polio vaccine
They are safer than attenuated vaccines because they cannot cause disease.
Toxoid vaccines contain inactivated toxins with formalin
Since the product is inactivated, booster shots are required. ex) DTaP

7. Subunit vaccines contain only those parts of the antigens that stimulate a strong immune response.
Recombinant DNA technology can be used to create recombinant subunit vaccines. ex) Hepatitis B
Subunits cannot cause disease.
Conjugate vaccines are created by attaching bacterial capsule polysaccharides to a toxoid.
They elicit a strong immune response. ex) Hib

8. Figure 22.04: Making a DNA Vaccine.
DNA vaccines depend on the ability of some cells to:
take up and translate foreign DNA.
display the resulting proteins, inducing a strong immune response.
Naked DNA vaccines contain engineered plasmids that contain a gene from a pathogen.
They are not infective or replicate, so cannot cause disease. ex) West Nile Virus for horses
Figure 22.04: Making a DNA Vaccine.

9. Childhood Immunization Schedules - 2012
Figure 22.03: Childhood (0-6 years) Immunization Schedule-2007.

10. Adult Vaccine Recommendations
Some adults might not have had childhood diseases
Newer vaccines may not have been available when some people were children
Immune system declines with increasing age
Some vaccines have limited protection, ex) flu
Figure 22.05: Vaccinations for Adults 2012.
Reproduced from: CDC

11. Figure 22.02C: Naturally Acquired Passive Immunity.
Adaptive immunity can also result by passively receiving antibodies to an antigen.
Naturally acquired passive immunity (congenital immunity) occurs when antibodies pass from mother to fetus.
Maternal IgG antibodies remain in the child 3–6 months after birth .
Maternal IgA antibodies also pass to the newborn through:
first milk (colostrum).
breast milk.
Figure 22.02C: Naturally Acquired Passive Immunity.

12. Figure 22.02D: Artificially Acquired Passive Immunity.
Artificially acquired passive immunity involves injection of antibody-rich serum into a body.
The serum can be used to:
prevent disease (prophylactic).
treat disease (therapeutic serum). ex) tetanus
The immune system may recognize foreign serum proteins as “nonself” and mount an allergic reaction.
Immune complexes may form and serum sickness may develop.
Figure 22.02D: Artificially Acquired Passive Immunity.

13. Figure 22.07ABC: Herd Immunity.
Herd immunity results from effective vaccination programs.
In herd immunity, the majority of a population are immune.
Unvaccinated individuals are unlikely to contact an infected individual.
Herd immunity is
affected by:
Population density.
Number vaccinated 85% herd immunity threshold
The strength of a
person’s immune
system.
Figure 22.07ABC: Herd Immunity.
Courtesy: National Institute of Allergy and Infectious Diseases

14. Do Vaccines Have Dangerous Side Effects?
Adverse reactions to vaccines are reported to the Vaccine Adverse Events Reporting System (VAERS).
People with egg allergies should not take flu vaccinations.
The risk of contracting a disease with death or disability is much greater than any risk associated with vaccines.
Figure MF01: Inoculating chicken eggs with a flu virus.
© James King-Holmes/Photo Researchers, Inc.

15. 22.2 Serological Reactions Can Be Used to Diagnose Disease
Serological reactions have certain characteristics.
Serology can help diagnose microbial infections.
Titration is the dilution
of antigen or antibody
solution to the most
favorable concentration.
The titer is the most dilute
concentration of serum
antibody that reacts to its antigen.
A rise in the titer ratio (antibody:serum) indicates disease.
Figure 22.08: The determination of titer.

16. Neutralization involves antigen-antibody reactions.
Neutralization is used to identify toxins and antitoxins, viruses and viral antibodies.
If a specific agent is suspected, to determine if the toxin has been neutralized, a sample can be:
mixed with an antitoxin.
injected into a lab animal.
Figure 22.09: Neutralization Test.

17. ex) of neutralization test
The Schick test is used to determine if a person is immune to diphtheria when the toxin is injected intradermally and no reaction is seen if the antibodies are present.

18. Figure 22.10: A precipitation test.
Precipitation requires the formation of a lattice between soluble antigen and antibody.
Precipitation reactions involve antigens and antibodies cross-linked in a huge lattice.
In fluid, the molecules diffuse until they reach the ideal concentration (the zone of equivalence).
In immunodiffusion, antigens and antibodies diffuse through a gel until they reach the zone of equivalence.
Figure 22.10: A precipitation test.

19. Figure 22.11: Immunoelectrophoresis.
In immunoelectrophoresis, diffusion is combined with electrophoresis.
Figure 22.11: Immunoelectrophoresis.

20. Agglutination involves the clumping of antigens.
A visible reaction requires less antibody or antigen if they are clumped together.
In passive agglutination:
antigens are adsorbed onto a surface.
antibodies are added.
agglutination is observed.
Figure 22.12AB: Passive agglutination tests.

21. Hemagglutination is used to: determine blood type.
detect viruses that cause agglutination of red blood cells.
Figure 22.12D: Blood type can be determined using the agglutination test.
© Ed Reschke/Peter Arnold, Inc.

22. Complement fixation can detect antibodies to a variety of pathogens.
Figure 22.13: The complement fixation test.

23. Labeling methods are used to detect antigen–antibody binding.
Immunofluorescence antibody test can detect antigen–antibody binding by labeling antibodies with a fluorescent marker.
Figure 22.15: The indirect immunoluorescence antibody test (IFA) for Diagnosing Syphilis.

24. Figure 22.16: The radioallergosorbent test (RAST).
The radioimmunoassay (RIA) is extremely sensitive, using radioactivity-labeled antigens.
The radioallergosorbent test (RAST) uses radioactive antiglobulin antibodies.
Figure 22.16: The radioallergosorbent test (RAST).

25. The enzyme-linked immunosorbent assay (ELISA) is similar to RAST.
It uses an enzyme system instead of radioactivity.
It is often used to detect antibodies against HIV.
Figure 22.17: The ELISA.

26. 22.3 Monoclonal Antibodies Are Used for Immunotherapy
Monoclonal antibodies are becoming a “magic bullet” in biomedicine.
Polyclonal antibodies occur because there are multiple epitopes on a pathogen.
They activate different B cell populations.
Figure 22.18: The production of monoclonal antibodies.
Insert image courtesy of Abbott Laboratories

27. Myeloma cells are fused to an activated B cell to form a hybridoma.
In the lab, antibodies recognizing one epitope (monoclonal antibodies [mAb]) are produced using myelomas.
Myeloma cells are fused to an activated B cell to form a hybridoma.
A hybridoma producing the desired mAb can be cloned.
mAbs can be used in:
disease prevention.
immunomodulation (controlling overactive inflammatory responses).