Week 8 - Immunity and Immunization Flashcards
Define immunology.
Study of the components and function of the immune system
What makes up the immune system? What does it protect against?
Molecules, cells, tissues and organs which provide non-specific and specific protection against microorganisms, microbial toxins, tumor cells
Crucial to human survival
What are the 5 roles of the immune system?
Defense against infections
Defense against tumors
Clearance of dead cells and tissue repair
Can injure cells and induce pathologic inflammation
Recognizes and responds to tissue grafts and newly introduced proteins
What are the 2 implications of defense against infections?
Deficient immunity results in increased susceptibility to infections; exemplified by AIDS
Vaccination boosts immune defenses and protects against infections
What is the implication for defense against tumors?
Potential for immunotherapy of cancer
What is the implication of clearance of dead cells and tissue repair?
Deficient immunity can lead to secondary infections after injury, and excessive immune responses can lead to fibrosis and organ dysfunction
What is the implication of the immune system can injure cells and induce pathologic inflammation?
Immune responses are the cause of allergic, autoimmune, and other inflammatory diseases
What is the implication of the immune system recognizing and responding to to tissue grafts and newly introduced proteins?
Immune responses are barriers to transplantations and gene therapy
What are the 2 kinds of immune response? What are the 2 kinds of acquisition of immunity?
Immune response:
Innate (non-specific): first line of defense in response to all pathogens
Adaptive/acquired (specific): secretes antibodies to specifically target a pathogen
Acquisition of immunity: natural and artificial
What is the innate immune system? What are the 2 lines of innate defenses?
Innate: structural defenses; responds to nonspecific foreign substances
First line: external surface epithelium & membranes
Second line: inflammatory processes (antimicrobial proteins, phagocytes, fever, inflammation, and NK cells)
What are the 5 steps of phagocytosis?
- Microbe adheres to phagocyte
- Phagocyte forms pseudopods that eventually engulf the particle
- Phagocytic vesicle is fused with a lysosome and creates a phagolysosome
- Microbe infused vesicle is killed and digested by lysosomal enzymes within the phagolysosome, leaving a residual body
- Indigestible and residual material is removed by exocytosis
Defne active immunity.
Long-lasting protection (memory) and multiple effector mechanisms activated
Define passive immunity and give an example.
Rapid protection and short duration
Example: injection of globulins, antibody passage through mother’s milk to infant, or passage of antibodies to baby from placenta
Define adaptive immune system.
Responds to specific foreign substances
Adaptive defenses: B-cells (humoral immunity) and T-cells (cellular immunity)
T-cells: T-helper cells and T-cytotoxic cells; attack pathogen directly and do not secrete antibodies
Antigen presenting cells: macrophages, dendritic cells, B lymphocytes, etc.
What are the 7 features of adaptive immune responses?
Specificity
Diversity
Memory
Clonal expansion
Specialization
Contraction and homeostasis
Nonreactivity to self
What are the functional significances of each of the 6 features of the adaptive immune responses?
Specificity
Diversity
Memory
Clonal expansion
Specialization
Contraction and homeostasis
Nonreactivity to self
Specificity: ensures that distinct antigens elicit specific responses
Diversity: enables immune system to respond to a large variety of antigens
Memory: leads to enhanced responses to repeated exposures to the same antigens
Clonal expansion: increases number of antigen-specific lymphocytes to keep pace with microbes
Specialization: generates responses that are optimal for defense against different types of microbes
Contraction and homeostasis: allows immune system to respond to newly encountered antigens
Nonreactivity to self: prevents injury to the host during responses to foreign antigens
What two features best distinguish adaptive and innate immunity?
Specificity and memory
What are the 4 details (2 for observational and 2 for implications) about Edward Jenner?
Jenner observes that dairy maids who had been infected with cowpox – a disease with similar but milder symptoms than smallpox – appear immune to smallpox infection
Experiment: Inoculation with cowpox material in 8-year-old boy and challenge 6 weeks later with smallpox
Jenner did not have knowledge of the causative agent of smallpox – his work was strictly empirical, yet highly effective in controlling smallpox
Serious issues with regard to informed consent
What are the 7 prerequisites for an effective vaccine?
- A natural model of effective immunity and response should be life-long
- Safety: vaccine must pose little risk
- Minimal immune evasion: if the microbe changes epitopes, a vaccine is likely to become ineffective
- Practical to manufacture: is mass production feasible?
- Durability: is the vaccine’s protection “durable” (long lasting)?
- Practice use: is administration practical? Example: preservation, refrigeration need, etc.
- Cost: is the vaccine affordable? Is there a “market”?
How do vaccines work when compared to the natural model of infection?
Natural model of infection:
1. Disease causing microorganism infects host
2. Host has an immune response
3. Recovery, death, or disability and immune memory
Vaccination:
1. Vaccine antigen is introduced
2. Antigen causes immune response without infection
3. Host recovers and gains immune memory
What are the 7 types of vaccines?
Inactivated vaccines
Live, attenuated vaccines
Subunit vaccines
Toxoid vaccines
Conjugate vaccines
mRNA Vaccines
DNA vaccines
What are 3 details about inactivated vaccines? What are the concerns? Give an example.
The disease-causing microbe is killed with chemicals, heat, or radiation
Such vaccines are more stable and safer than live vaccines; the dead microbes can’t mutate back to their disease-causing state
Inactivated vaccines usually don’t require refrigeration, and they can be easily stored and transported
Concerns: incomplete inactivation, less than optimal immune response
Example: injected Polio vaccine
Explain the Cutter incident.
1940s: inactivated polio vaccine had circumstances that did not lead to a complete inactivation of the polio virus
Vaccine administered to children all over the U.S.
Results: 40,000 cases of polio, 200 children with varying degrees of paralysis, and 10 deaths
Future implication: creating of FDA oversight into manufacturing and safety of vaccines
What are 3 details about live attenuated vaccines? What are the concerns? Give an example.
The microbe that has been weakened in the lab so it can’t cause disease
Because a live, attenuated vaccine is the closest thing to a natural infection, these vaccines are good “teachers” of the immune system
They elicit strong cellular and antibody responses and often confer lifelong immunity with only one or two doses
Concerns: reversion, contraindications for some patients, refrigeration
Example: polio vaccine (oral), measles, mumps, chicken pox
What are 3 details about subunit vaccines? What are the concerns? Give an example.
Include only the antigens that best stimulate the immune system; in some cases, these vaccines use epitopes—the very specific parts of the antigen that
antibodies or T cells recognize and bind to
Less likely to produce adverse effects as many components are eliminated
Produced by either: 1) grow the microbe in the laboratory and then use chemicals to break it apart, or 2) manufacture
the antigen molecules from the microbe using recombinant DNA technology (vaccines produced this way are called
“recombinant subunit vaccines”)
Concerns: Have you selected the most immunogenic epitopes? Are the “epitopes” constant, or do they change?
Example: Hepatitis B vaccine
What are 2 details about toxoid vaccines? What are the concerns? Give an example.
For bacteria that secrete toxins, or harmful chemicals, a toxoid vaccine may be appropriate; used when a bacterial toxin is the main cause of illness
The toxin is formalin-inactivated, administration can induce an antibody response which later protects the individual from the effects of the toxin
Concerns: it must be possible to effectively clear the bacterial infection
Examples: Diphtheria, tetanus
What are 2 details about conugate vaccines? Give an example.
If a bacterium possesses an outer coating of sugar molecules called polysaccharides, these can disguise bacterial antigens so that the immature immune systems of infants and younger children can’t recognize or respond to them
Conjugate vaccines link antigens from a microbe to the polysaccharides
Examples: Hepatitis B, influenza (injection), Haemophilus influenza type b (Hib), Pertussis (part of DTaP combined immunization), Pneumococcal, Meningococcal
What are 4 details about the COVID-19 vaccine?
Coronaviruses have crown-like spikes on the surface (spike proteins) which are ideal targets for vaccines
mRNA is genetic material that tells your body how to make proteins
COVID-19 vaccine is made of mRNA wrapped in a coating that makes delivery easy and keeps the body from damaging it
mRNA in vaccine teaches body how to make copies of the spike protein and the body will recognize the real virus and know how to fight it off
What do vaccines contain? Give examples of preservatives and adjuvants in specific vaccines
In addition to the bulk antigen that goes into a vaccine, vaccines are formulated with other fluids (such as water or saline), additives or preservatives, and sometimes adjuvants
Preservatives: phenol (typhoid, pneumococcal polysaccharide), benzethonium chloride (anthrax), 2-phenoxyethanol (inactivated polio), and thimerosal (multi-dose influenza)
Adjuvants help the body create a stronger immune response
Adjuvants: aluminum salt (Hepatitis A and B, diphtheria, tetanus, acellular Pretusis combinations, Haemophilus influenzae type B, pneumococcal conjugate, and Japanese encephalitis, HPV), AS04 (aluminum salt and monophospholipid A) (HPV), and MF59 (oil in water emulsion; one vaccine) (H1N1 influenza)
What are 4 details about DNA vaccines? Give an example.
These vaccines utilize the microbe’s genetic material; in particular, DNA vaccines use the genes that code for those all-important antigens
When these genes are introduced into the body some cells will take up that DNA and produce the antigens and display them on their surfaces
In other words, the body’s own cells become vaccine-making factories, creating the antigens necessary to stimulate the immune system
Such vaccines remain experimental
Examples: flu, HIV, etc. (developmental stages only)
What two factors contribute to vaccine ability to control/eliminate a disease?
The effectiveness and the durability of the effect of the vaccine and level of vaccination coverage achieved in a given population
Define vaccine efficacy.
Measures the decrease in incidence of a disease in the vaccinated population compared to the incidence of the disease in the unvaccinated
Define herd immunity.
Form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a
measure of protection for individuals who have not developed immunity
Why do we not have vaccines for serious protozoal diseases like malaria or African sleeping sickness?
Complex life cycles and undergo “antigenic shift” (different antigens at different life cycles and it’s hard to find one that’s present in all life cycles)
Plasmodium causes malaria (mosquito is vector)
Trypanosoma causes African sleeping sickness (tsetse fly is vector)
What are 7 issues with vaccination?
Vaccine Adjuvants
Vaccines During Pregnancy
Vaccine Recalls
Febrile Seizures after Childhood Vaccinations
Guillain-Barré Syndrome (GBS)
Autism and Vaccines-Thimerosal (Preservative used in Some Flu Vaccines)
Multiple Vaccines and the Immune System
What are the 3 hypotheses for the relationship between vaccines and autism?
The combination measles-mumps-rubella vaccine causes autism by damaging the intestinal lining, which allows the entrance of encephalopathic proteins
Thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system
The simultaneous administration of multiple vaccines overwhelms or weakens the immune system
Define autism.
Group of complex neurodevelopment disorders characterized by repetitive and characteristic patterns of behavior and difficulties with social communication and interaction
Describe the Wakefield study and its limitations.
Described 8 children whose first symptoms of autism occurred within 1 month of receiving MMR vaccine
Premise was that measles virus caused invasion of “encephalopathic peptides” to enter through the GI tract and enter the brain
Study limitations: no control subjects, no blinding of assessments, MMR viruses had never been associated with loss of intestinal barrier function…and there was no evidence that “encephalopathic peptides” had ever travelled from intestine to brain to cause neurologic
damage
What are 3 details about the epidemiological investigation into Wakefield’s claims?
Multiple studies failed to corroborate Wakefield’s claims
2004: as UK vaccination rates drop from above 95% to 80%, ten of Wakefield’s coauthors issue retractions
In 2010, after years of stating they probably shouldn’t have published it, Lancet editors retract the paper, as fraud is charged in handling of every one of the 8 cases reported
What are examples of active and passives forms of naturally and artificially acquired immunity?
Naturally acquired:
Active: infection; contact with pathogen
Passive: antibodies pass from mother to fetus via placenta or to infant through milk
Artificially acquired:
Active: vaccine; dead or attenuated pathogens
Passive: injection of immune serum (gamma globulin)
What are the steps for how the adaptive immune system fights pathogens?
- Pathogen is encountered, macrophage encounters them, and presents them to B-cells
- B-cells differentiate to form plasma and memory B-cells
- Plasma cells secrete antibodies that bind to pathogens and cause clearance
- Memory B-cells remain dormant until they come into contact with the pathogen for a second time, then they quickly divide into plasma cells
What is the CDC’s recommended vaccination schedule for children and adults?
Children:
Hepatitis B: 1st dose at birth, 2nd dose 1-2 months, and 3rd dose at 6-18 months
Rotavirus, Tdap, Hib, pneumococcal, and inactivated polio: 1st dose at 1-2 months, 2nd dose at 4 months
Influenza: 2 doses at first, then 1 dose yearly
COVID-19: recommended for 6 months and above
Adults:
Influenza: every year
MMR: 1-2 doses depending on indication
Varicella: 2 doses
HPV: 2-3 doses depending on age at initial vaccination
Hep B: 2-4 doses depending on vaccine or condition
