Immune system and vaccines

Most pathogens..?

must overcome surface barriers and reach underlying tissues, also overcome 2 branches of host defense

Pathogen 2 branches of host defense are?

Innate resistance mechanisms and adaptive immune response

Immune system is composed of?

widely distributed cells, tissues, organs

What does the immune system do with foreign substances?

recognizes foreign substances or microbes and acts to neutralize or destroy them

What is immunity

ability of host to resist an infection or disease

What is immunology

study of immune responses and how they protect the host

2 types of immunity

innate and adaptive

Innate immunity barriers

physical, chemical, cellular defenses

Innate immunity details

first line of defense, resistance is generic, general mechanisms such as skin, mucus, lysozyme, and LACKS immunological memory

Adaptive immune response details

activated by cells of innate immunity, has "memory"--effectiveness increases on repeated exposure to agent, vaccines stimulate the adaptive response

what is the first line of defense against microbes and is non-specific?

the innate immune system

Barries or the innate immune system

skin, mucous membranes, resident bacteria, shedding of dead cells

Flushing membranes of innate immune system

coughing, tears, urination, defecation

What do cilia do when we inhale thousands of microbes per day?

sweep large molecules away from the lungs, toward the throat to be expelled by coughing or washed into the stomach via saliva

what happens to small microbes that make it to the lungs?

encountered by macrophages

what is the lymphatic system made of?

tons of specialized cells that do different things

What do antigens do to a immune system?

turn on the immune system

A molecule that triggers an immune response?

chemicals, bacteria, viruses

What can one antigen have?

multiple epitopes

What is an epitope?

3-D parts that react with a specific antibody

what is an antibody

Y-shaped proteins that are produced by the adaptive immune system in response to antigens

Antibody Affinity

strength with which antibody binds to its antigen

Hapten

small molecule that becomes immunogenic when bound to a protein (penicillin)

Adaptive immunity have?

Lymphocytes

2 types of cells within Lymphocytes

B cells and T cells

B cells

produce antibodies

T cells

kill infected cells (CD8+), stimulate B-cells through CD4+

5 types of B cells?

IgG, IgD, IgM, IgA, IgE

IgG

80% of serum immunoglobulin; only Ig that can cross the placenta

IgD

preset on B-cells; signals B-cells to start antibody production

IgM

First Ig in all immune responses; present as individual units or as pentamers

IgA (secretory IgA

most abundant antibody because it is secreted across mucosal surfaces (tears, saliva sweat)

IgE

involved in allergic responses

What is the primary immune response?

The immune response to the first exposure to an antigen.

What is the secondary immune response?

A faster, stronger response to a second exposure to the same antigen.

Which antibody is produced first?

IgM.

What happens during class switching?

B cells switch from producing IgM to IgG without changing antigen specificity.

What are memory B cells?

Cells that remain after exposure and help the body respond faster to the same antigen again.

What happens during the decline phase?

Antibody levels decrease as the antigen is eliminated.

Which antibody usually dominates the secondary response?

High-affinity IgG.

Why is the secondary response faster and stronger?

Memory B cells recognize the antigen and respond rapidly.

latent period in primary and secondary antibody immune responses

B cells are activated in lymphoid tissues

Log phase in primary and secondary antibody immune responses

IgM is secreted first but it is a "generic" Ab with low affinity to antigen

Plateau in primary and secondary antibody immune responses

B cells undergo "Ab class switching" (IgM reduced, but increase in high affinity IgG in serum)

Decline in primary and secondary antibody immune responses

antibody-antigen complex are eliminated by phagocytic cells (low levels of memory B cells stay present)

Secondary response

more rapid, specific, and sustained response, higher titer

How has vaccination affected polio cases?

Vaccination dramatically reduced polio cases in the United States to nearly zero.

What is herd immunity?

When enough people in a population are immune to a disease, reducing its spread.

What percentage of the population needs immunity for polio herd immunity?

80-85%.

What percentage of the population needs immunity for measles herd immunity?

About 95%.

Why do different diseases require different levels of herd immunity?

Some diseases spread more easily than others.

vaccine definition from the World Health Organization (WHO)

A preparation that improves immunity to a specific disease, often containing weakened or killed agents, toxins, or surface proteins

Vaccine definition from CDC

A suspension of live (attenuated) or inactivated microorganisms (or parts of them) administered to induce immunity and prevent disease.

Vaccine definition from Johns Hopkins

A substance that introduces the body to an ingredient

mimicking a pathogen to prompt an immune response

What are the five main types of vaccines?

Inactivated, live-attenuated, subunit/recombinant/polysaccharide/conjugate, toxoid, and viral vector vaccines.

What are adjuvants?

Ingredients added to vaccines to enhance the immune response.

Why are adjuvants added to vaccines?

To strengthen the immune response and allow smaller amounts of antigen to be used.

What are two examples of adjuvants?

Aluminum salts and MF59 (squalene oil).

What are inactivated vaccines?

Vaccines containing killed pathogens that cannot reproduce.

What are live-attenuated vaccines?

Vaccines containing weakened, living pathogens.

What are subunit vaccines?

Vaccines containing specific parts of a pathogen.

What are recombinant vaccines?

Vaccines made using genetic engineering to produce pathogen antigens.

What are polysaccharide vaccines?

Vaccines containing sugar molecules from a pathogen's outer coating.

What are conjugate vaccines?

Vaccines that attach pathogen sugars to proteins to improve the immune response.

What are toxoid vaccines?

Vaccines containing inactivated toxins that stimulate immunity.

What are viral vector vaccines?

Vaccines using a modified virus to deliver genetic instructions for an antigen.

What are inactivated vaccines?

Killed microbes that are less immunogenic and often require multiple doses.

What are attenuated vaccines?

Weakened, living microbes that mimic natural infection and may require only one dose.

What are the advantages of attenuated vaccines?

They closely mimic natural infection and produce a strong immune response.

What are three disadvantages of whole-cell vaccines?

More adverse reactions, risk to immunosuppressed people, and attenuated microbes may revert to virulence.

What does it mean if a pathogen reverts to virulence?

It regains its ability to cause disease

What are acellular or subunit vaccines?

Vaccines containing purified molecules or specific parts of a pathogen.

Why are some subunit vaccines called recombinant vaccines?

They are developed using genetic engineering.

What are three forms of vaccine subunits?

Polysaccharides, recombinant surface antigens, and inactivated exotoxins (toxoids).

Why do subunit vaccines often require booster doses?

They generally produce a weaker or less durable immune response than live vaccines.

What are toxoid vaccines?

Vaccines containing inactivated bacterial toxins.

What are examples of diseases prevented by subunit vaccines?

Hepatitis B, HPV, Hib, meningococcal disease, and pneumococcal disease.

What is one limitation of vaccines regarding immunity?

They may produce systemic immunity but not enough mucosal immunity, or vice versa.

How does the route of vaccine administration affect immunity?

Oral or inhaled vaccines can stimulate mucosal immunity, while injections mainly stimulate systemic immunity.

Which two types of cells must adaptive immunity activate?

T cells and B cells.

Why is complete B-cell activation important?

It allows B cells to produce antibodies against specific antigens.

What is a risk of live-attenuated vaccines?

The weakened pathogen may revert to a disease-causing form.

What is an example of vaccine reversion?

The oral Sabin polio vaccine can rarely revert to a virulent form and cause outbreaks.

What is another limitation of vaccine production?

Ethical concerns.

What is a primary cell line?

Cells taken from tissue that survive only a limited time in culture.

What is an immortal cell line?

Cells that can continue dividing indefinitely in culture.

What cell line was used to produce the Johnson & Johnson COVID-19 vaccine?

The PER.C6 cell line.

Where did the PER.C6 cell line originate?

Retinal tissue from an aborted 18-week-old fetus in the Netherlands in 1985.

Why can immortal cell lines be used for vaccine production?

They can divide indefinitely, allowing researchers to grow large numbers of cells.

What ethical concern does this slide raise?

The use of cell lines derived from fetal tissue following an abortion.ss

How does the Johnson & Johnson COVID-19 vaccine work?

Uses a modified, non-replicating virus to deliver DNA instructions for the spike (S) protein.

How do the Pfizer and Moderna vaccines work?

Use mRNA inside lipid nanoparticles to instruct cells to make the spike protein.

What is the purpose of sugars and salts in vaccines?

Help stabilize the vaccine and maintain its structure.

What is PEG in mRNA vaccines?

Polyethylene glycol, an ingredient in lipid nanoparticles that can cause allergic reactions in some people.

What is polysorbate in the Johnson & Johnson vaccine?

An emulsifier that can cause allergic reactions in some people.

What are extracellular vesicles?

Structures cells naturally use to transport materials, such as proteins and RNA.

What is the main difference between the Johnson & Johnson and mRNA vaccines?

Johnson & Johnson uses DNA delivered by a viral vector; Pfizer and Moderna use mRNA delivered by lipid nanoparticles.