Download - Chap20 Immunology & Serology
Immunity and Serology
Chapter 20
2
• Immunity is a condition under which an individual is protected from the disease
• Two general types of immunity• Innate Immunity• Acquired Immunity
• Types of Acquired Immunity• ACTIVE IMMUNITY
• Naturally Acquired Active Immunity• Artificially Acquired Active Immunity
• PASSIVE IMMUNITY• Naturally Acquired Passive Immunity• Artificially Acquired Passive Immunity
3
4
• Naturally acquired active immunity develops from exposure to an infectious agent• 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
• 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
5
• Live, attenuated vaccines contain weakened microbes that multiply at only low levels, inducing a strong immune response
• Organisms can revert to a virulent form and cause disease
• A single-dose vaccine can combine vaccines for different diseases
• Vaccines using attenuated bacteria are difficult and not widely used
6
• Inactivated vaccines contain killed pathogens, which induce a weaker immune response• Booster shots are required to maintain immunity
• They are safer than attenuated vaccines because they cannot cause disease
• Toxoid vaccines contain inactivated toxins (toxoids)• Since the product is inactivated, booster shots are
required• Prepared by incubating toxins with a chemical
*to avoid multiple injections, vaccines are combined into single-dose vaccine
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
• Subunits cannot cause disease
• Conjugate vaccines are created by attaching bacterial capsule polysaccharides to a toxoid• They elicit a strong immune response
8
• 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 replicative, so cannot cause
disease
• Recombinant vector vaccines involve DNA incorporated into an attenuated pathogen• The pathogen:
• takes the DNA into the cells (viral vector) or • incorporates the DNA and present antigens (bacterial vector)
*Adjuvants : increase efficacy of a vaccine or toxoid by increasing availability of the antigen in the lymphatic system. = stimulate phagocytic activity, IL 1 activation, sustained immune response
9
Childhood and Adolescent Immunization Schedule - 2006
10
• Passive Immunity develops when antibodies enter the body from outside source
• Two Types: NATURAL OR ARTIFICIAL
• 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 antibodies also pass to the newborn through:
• first milk (colostrum) • breast milk
11
• 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)
• Antiserum: hyperimmune serum or convalescent serum
• The immune system may recognize foreign serum proteins as “nonself” and mount an allergic reaction• Immune complexes may form and serum sickness
may develop
12
• 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 • the strength of a
person’s immune system
13
• People with egg allergies should not take flu vaccinations
• The risk of contracting a disease is much greater than any risk associated with vaccines
• Thimerosal
14
• Serology: branch of immunology that studies serological reactions
• Serological reactions can help diagnose microbial infections
• Ag-Ab reactions are studied under laboratory conditions
• Uses patient’s serum
• Function: confirmatory test, detect organism in tissue, aid MD in following course of disease and determine immune states
15
• 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
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• Example: detection of botulinum toxin in food
• The Schick test is used to determine if a person is immune to diphtheria (intradermal test)
17
• 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• Oudin tube technique• Ouchterlony plate
technique
18
• In immunoelectrophoresis, diffusion is combined with electrophoresis
19
• Agglutination – antibodies interact with antigens on a surface of a particular object and cause object to clump together.
• 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
20
• Hemagglutination is used to:• determine blood type • Detect viruses that cause agglutination of red blood
cells• Flocculation : precipitation and agglutination; Ag exists
in a non-cellular particulate form that reacts with antibodies to yield large, visible aggregates.
21
• Complement Fixation Can Detect Antibodies to a Variety of Pathogens
22
• Labeling Methods Are Used to Detect Antigen-Antibody Binding• A fluorescent
antibody technique can detect antigen-antibody binding by labeling antibodies with a fluorescent marker
• Can be direct or indirect (FTA-ABS)
23
• The radioimmunoassay (RIA) is extremely sensitive, using radioactivity-labeled antigens; based on the competition between radioactive labeled Ag and unlabeled Ag for the reactive sites on Ab molecule
• The radioallergosorbent test (RAST) uses radioactive antiglobulin antibodies
24
• The enzyme-linked immunosorbent assay (ELISA) is similar to RAST • It uses an enzyme
system instead of radioactivity (horseradish peroxidase)
• It is often used to detect antibodies against HIV
25
• 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
26
• In the lab, antibodies recognizing one epitope (monoclonal antibodies [mAb]) are produced using myelomas
• Myeloma cells are fused to and 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)
27
• Gene Probes Are Single-Stranded DNA segments
• They hunt down complementary DNA fragment and emit a signal
• The polymerase chain reaction (PCR) is used to increase the amount of DNA to be searched
• Gene probes and PCR are use in:
• HIV and HPV detection
• water-quality tests