Adaptive Immunity & Vaccinations

Where are B-cells located?

outside cells

Where are T-cells located?

inside cells

Acquired specific immunity

• product of B & T lymphocytes

• lymphocytes undergo a selective process that specializes them for reacting to only one specific antigen/immunogen

Immunocompetence

• the ability of the body to react with countless foreign substances

What are antigens/immunogens?

molecules that stimulate a response by T & B cells

What can be an antigen?

any exposed or released protein or polysaccharide is potentially an antigen

Do our own antigens evoke responses from our immune system?

Usually not

Specificity

highly specific to the antigen against which the 3rd line of defense is directed

Memory

the rapid mobilization of lymphocytes that have been programmed to recall their first engagement with invader & rush to the attack again

What are the principle stages of immunologic development & interaction?

• lymphocyte development & differentiation

• presentation of antigens

• challenge of B & T lymphocute by antigens

• B-lymphocyte response

• T-lymphocyte response

B-lymphocyte response

• humoral response

• production & activities of antibodies

T-lymphocyte response

• cell-mediated immunity

• killing

Humoral immunity

involves B-cell production of antibodies that bind antigens resulting in either neutralization, lysis, or phagocytosis/destruction

cell-mediated immunity

• involves T-cell recognition of abnormal antigens on the surface of host cells (indicating viral infection or tumorigenic change & the killing of infected cells

Tissue dendritic cells

• ingest the antigen

• migrate to the nearest lymphoid organ

• process & present antigen to T-lymphocytes

What are the 3 antigen presenting cells?

B-cells, dendritic cells, macrophages

What happens when B & T-cells are challenged by an antigen?

they proliferate & differentiate

Clone

• proliferation of a particular lymphocyte

• genetically identical cells (some are memory cells)

What are the three major types of T-cells?

• Helper T-cells

• killer/cytotoxic T-cells

• regulatory T-cells

Helper T-cells

stimulate B-cells to amke antibodies & help killer cells

Killer/cytotoxic T-cells

directly kill cells that have already been infected by a foreign invader

Regulatory T-cells

suppress immune response when no longer needed

What are the two steps that occur when B-cells respond to an antigen? Describe them.

1) when activated by an antigen, a B-cell divides, giving rise to plasma cells

• plasma cells have same reactive profile

• release antibodies into tissue & blood

• attach to antigen for which they’re specific & mark for destruction

2) Presentation of antigens

Antigen

a substance that provokes an immune response in specific lymphocytes

What are the requirements for a substance to be perceived as an antigen?

it must meet certain requirements in foreignness, shape, size, & accessibility

antigenicity

Property of behaving as an antigen

What does it mean that antigens must be perceived as foreign?

• whole microbes or their parts

• cells or substances from other humans, animals, plants, & molecules of complex composition

  • proteins/protein-containing compounds more immunogenic than repetitious polymers composed of a single unit

Autoantigens

normally present in the body but are mistakenly attacked by the immune system

Endogenous antigens

produced within cells due to infection

• viral cells

Exogenous antigens

enter the body from the outside

• bacteria

Tumor antigens

found on cancerous cells, triggering immune response

What are the chemical categories of antgens? (5)

• proteins, polypeptides

  • enzymes, cell surface, hormones, exotoxins, structures

• lipoproteins

  • cell membranes

• glycoproteins

  • blood cell makers

• nucleoproteins

  • DNA complexes to proteins

• polysaccharides (certain bacterial capsules) & lipopolysaccharides

Why is molecular shape & size significant in creating an immune response?

substances must be large & complex enough to catch the attention of surveillance cells & initiate an immune response

Epitope

• a portion of the antigen molecule recognized & responded to by a lymphocyte

• primary signal that a molecule is foreign

Haptens

• Consist only of a determinant group

• too small by themselves to elicit an immune response

• if linked to carrier group, the combined molecule develops immunogenicity

Naturally acquired active immunity

• antibodies are produced in response to antigen

• takes several days

• survivors of Black Death

naturally acquired passive immunity

• antibodies are received thru the placenta or breast milk

artificially acquired active immunity

• attenuated (live/killed) vaccine or DNA-altered agent is injected into the body

• Polio vaccine

Vaccine theory

• weakened form of disease injected into the body

• body makes antibodies to fight the invaders

• if the disease germs attack, the antibodies return to destroy them

Vaccination

• exposing a person to a material that IS antigenic, but NOT pathogenic

What discovery was an important development in medical science?

Discovery of vaccination

What are the basic principles of vaccination?

• stimulate primary immune response that primes the immune system for future exposure to a virulent pathogen

• if the pathogen later enters the body, the secondary immune response will be immediate, powerful, & sustained

artifically acquired passive immunity

• short-term immunization - usually given after exposure

• antibody-containing serum from a person or animal

• tetanus, rabies

What are some of the principles of vaccine preparation?

• should have a low level of adverse side effects or toxicity, and should not cause serious harm

• should protect against exposure to natural/wild forms of pathogen

• should stimulate antibody (B-cell) response & cell-mediated (T-cell) response

• should have long-term, lasting effects (memory)

• should be inexpensive, easy to administer, & have a long shelf life

• should not require numerous doses or boosters

What are the two categories of vaccines

whole organism & part-of-organism

whole cells or viruses in vaccines

• live, attenuated cells or viruses

  • MMR vaccine

• Killed cells or inactivated virus

  • influenza vaccine

Part-of-organism preparations

antigen molecules derived from bacterial cell or viruses (subunits)

• Pneumococcal vaccine,Meningitis vaccine, Anthrax, Hep B

What can the subunits be in part-of-organism vaccines?

• subunits from cultures of cells or viruses

• subunits chemically synthesized to mimic molecules found on pathogens

• subunits manufactured via genetic engineering

• subunits conjuaged w proteins to make them more immunogenic

• toxoid vaccines

conjugated vaccine

subunits conjugated w proteins (often from other microbes) to make them more immunogenic

toxoid vaccines

toxin from exotoxin of bacteria that is denatured

• diptheria, tetanus, pertussis

How does the COVID-19 Vaccine work? (mRNA vaccine)

• mRNA vaccines introduce the mRNA for an important protein from the virus that the vaccine is trying to protect against

• Spike protein of SARS-CoV-2 virus

• mRNA that codes for the SARS-Co-V-2 spike protein is taken up by dendritic cells which express the spike protein on the cell surface travel to lumph node & stimulate cells of immune system to make antibodies

  • these antibodies protect us if we get exposed in the future

True or false? Dozens of bacterial, viral, protozoan, & fungal diseases do NOT have a functional vaccine.

True

• Malaria, HIV/AIDS, worm infestations, various dairrheal diseases, respiratory disease

Why are most existing vaccines out of reach for much of the worlds population?

some people don’t have access to vaccines

common side effects of vaccines (3)

• local reactions at the injection site

• fever

• allergies

What are some relatively rare side effects of vaccines?

• Panencephalitis (from measles vaccine)

• black-mutation to a virulent strain (polio vaccine)

• diseases due to contamination w dangerous viruses or chemicals

• neurological effects of unknown cause (pertussis & swine flu vaccinations)

• allergic reactions to eggs or tissue culture

What complications have people tried to link to childhood vaccines? Why is this a problem? What are scientists doing to address this issue?

• some have attempted to link childhood vaccinations w diabetes, autism or asthma

• public debates about vaccine safety

• difficult for parents & consumers to discriminate between good & bad info

• scientists trying to address parent fears & provide reliable info

Autism & MMR vaccine

• Institute of Medicine published results of comprehensive examination of childhood vaccines

• MMR vaccine doesn’t cause autism

What is an example of the results of unfounded vaccine fears?

outbreaks of measles, mumps, diptheria, polio, typhoid fever, & whooping cough all over the US

• college dorms

• antivaccination religious communities

• antivax groups

Herd immunity

idea that those who are vaccinated will protect those who can’t be vaccinated.

• microbe does not spread w a sufficient amount immune individuals

When is vaccinating most prominent?

In childhood

What are some reasons why adults need vaccinations still?

• boost an older immunization

• protect against “adult” infections such as penumonia

• provide special protection in people w certain medical conditions

What vaccine preventable diseases are on the rise?

measles, yellow fever, polio, diptheria