Foundations in Microbiology

Chapter16

PowerPoint to accompany

Fifth Edition

Talaro

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Immunization and Immune Assays

Chapter 16

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Immunotherapy – preformed Ab

Immune serum globulin – (gamma globulin) contains immunoglobulin extracted from the pooled blood of at least 1,000 human donors

• Treatment of choice for preventing measles, hepatitis A and replacing Ab in the immune deficient

• Lasts 2-3 months

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Immunotherapy – preformed Ab

Specific immune globulin- prepared from convalescent patients in a hyperimmune state

• Contains high titer of specific Ab• pertussis, tetanus, chickenpox, hepatitis B• sera produced in horses are available for

diphtheria, botulism, spider and snake bites• act immediately & can protect patients for

whom no other useful medication exists

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Vaccines

• Provide an antigenic stimulus that does not cause disease but can produce long lasting, protective immunity

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Serology• A science that attempts to detect signs of infection in a

patient’s serum such as Ab for a specific microbe• Serological tests based on Abs specifically binding to

Ag. – Ag of known identity will react with Ab in an unknown

serum sample.– Known Ab can be used to detect Ag in serum

• Ag-Ab reactions are visible by clumps, precipitates, color changes or release of radioactivity.

• The most effective tests have high specificity and sensitivity.

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Types of serological tests

1. Agglutination tests2. Double diffusion precipitation tests3. Immunoelectrophoresis4. Western blot tests5. Complement fixation tests6. Immunofluorescence testing7. Immunoassays

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Types of serological tests

1. Agglutination tests – Ab cross-links whole cell Ag, forming complexes that settle out and from visible clumps in the test chamber– blood type, some bacterial & viral diseases

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2. Double diffusion precipitation tests involve the diffusion of Ags and Abs in a soft agar gel, forming zones of precipitation where they meet

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3. Immunoelectrophoresis – migration of serum proteins in gel is combined with precipitation by Ab

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4. Western blot test – separates Ag into bands. After the gel is affixed to a blotter, it is reacted with a test specimen and developed by radioactivity or with dyes

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5. Complement fixation tests detect lysins- Ab that fix complement and can lyse target cells. Involves mixing test Ag and Ab with complement and then with sensitized sheep RBCs.

If complement is fixed by the Ag-Ab, the RBCs remain intact and the test is positive.

If RBCs are hemolyzed, specific Ab are lacking and the test is negative.

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6. Immunofluorescence testing uses fluorescent Ab either directly or indirectly to visualize cells or cell aggregates that have reacted with the FAbs

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7. Immunoassays are highly sensitive tests for Ag and Ab.

Radioimmunoassay –Ag or Abs are labeled with radioactive isotopes and traced

Enzyme-linked immunosorbent assay (ELISA) can detect unknown Ag or Ab by direct or indirect means. A positive result is visualized when a colored product is released by an enzyme-substrate reaction.

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• Tests can differentiate B cells from T cells and their subtypes.