Immunity and Vaccines Flashcards
What is passive immunity?
Protection transferred from another person or animal.
(Temporary)
What is active immunity?
Protection produced by the person/animals own immune system.
(Longer-term protection)
How is passive immunity acquired?
Transfer of antibodies via colostrum/milk/placenta
What antibodies are seen in passive immunity?
IgA (mucosal immunity) and IgG (serum immunity)
What diseases use passive immunity as treatment?
- Tetanus
- Hepatitis A and B
- Immunodeficencies
Why does passive immunity end?
Due to catabolism of antibodies
How does active immunity work?
Infection by a pathogen and subsequent resolution leads to the production of memory T and B plus plasma cells. Second infection of the same pathogen leads to a stronger, faster and more specific reaction.
What are the two ways in which active immunity can be caused?
-Natural Infection (Immunological memory but also symptoms/ pathology)
-Vaccination (still want strong immunological memory but no/very limited symptoms)
What are the requirements of vaccines for active immunity to occur?
- mimic natural infection (to activate immune system)
- limit side effects
What are adjuvants?
Any substance that when given with an antigen enhances the immune response to that antigen. (Used in vaccines)
How do adjuvants aid vaccines?
- reduce the amount of antigen required to induce protection
- increases the speed and magnitude of the response
How does the Alum adjuvant work?
- slow release antigen
- can lead to DAMPS activating dendritic cells and macrophages
- Mainly TH2 activation (not cell mediated)
What are the three vaccine approaches?
- live attenuated vaccine
-killed vaccine
-subunit vaccines including toxoid vaccines
How do live attenuated vaccines work?
- still viable but reduced pathogenicity
- can cause infection but not disease
- strong, appropriate immune response
- cellular immunity
- humoral immunity (antibody mediated immunity)
- long lasting immunity
What are the advantages of using the live attenuated vaccine?
- Multiple antigens
- Few immunisations
- Easy to produce without genome of pathogen
- May not require adjuvant
How does the killed vaccine work?
- Pathogens are killed by heat (which can denture too many proteins antigens)
-Pathogens are killed by chemicals (formaldehyde) - weaker immune response (compared to live vaccines)
- good serum antibody response (little secretory IgA)
- Poor cell-mediated immunity created
- Booster shots usually required
What are the advantages of using killed vaccines?
- multiple antigens
- stable
- safer than live vaccine
- no refrigeration required
What are the disadvantages of using killed vaccines?
- Benn inefficient in the past
- lack of understanding about why it protects
- contamination with animal viruses (polio)
- initial preparation requires working with pathogen
How do subunit and toxic vaccines work?
- specific purified pathogen subunit/ molecule
- toxoid vaccines induce antibodies against the bacterial exotoxins
- exotoxins can cause major symptoms
- weak immune response
- good serum antibody response
- no cell-mediated immunity
- booster shots required
What are the advantages of using subunit and toxoid vaccines?
- limited antigens (less chance of cross reactivity)
- higher levels of safety and reproducibility
- no need for refigeration
What are the issues with using subunit and toxoid vaccines?
- Toxoid = limited to a few bacterial diseases
- difficult to develop
- adjuvant required
