Immunity and how vaccines work

Question 1

What is a vaccination?

Answer 1

This means having the vaccine- actually getting the vaccine.

Question 2

What is immunisation?

Answer 2

Means both receiving a vaccine and becoming immune to disease, as a result of being vaccinated.

Question 3

What is the aim of a vaccine?

Answer 3

To produce the same immune protection which usually follows natural infection but without causing disease.
To cause long-lasting immunity
To interrupt the spread of infection.

Question 4

What are examples of innate immunity?

Answer 4

Innate (natural) immunity
Physical barriers: skin and mucous membranes
Chemical barriers- gastric and digestive enzymes
Cellular and protein secretions- lysosomes, compliment, interferons, macrophages and white blood cells.
Defining characteristics: no memory persists afterwards.

Question 5

What is adaptive immunity?

Answer 5

Adaptive (acquired) immunity
The second level of defence.
Increases in strength and effectiveness with each encounter. The foreign agent is recognised in a specific manner and the immune system acquires memory of it.

Question 6

What is passive immunity?

Answer 6

Natural meternal transfer of antibodies to infant via placenta.
Artificial administration of preformed substance to provide immediate but short-term protection (e.g. immunoglobulin, antitoxin)

Question 7

What is active immunity?

Answer 7

Natural following contact with the organism. Artificial administration of agent to stimulate immune response (immunisation). Acquired through contact with microorganism/ antigen. Protection produced by the individual’s own immune system. Protection often life-long but may need boosting.

Question 8

What is the body’s initial defence against infection?

Answer 8

Immune system is a complex network of cells and organs. The initial defence are white blood cells called macrophages (“big eaters”). They eat as many of the infecting micro-organisms as they can. Also called innate/ natural killer cells.

Question 9

How is a microorganism recognised as foreign?

Answer 9

Organism is recognised as “foreign” because of unique molecules on its surface antigens.

Question 10

What is an antigen?

Answer 10

A live or inactivated substance (e.g. protein or polysaccharide) capable of producing an immune response. Anything that can be bound by an antibody.

Question 11

What are macrophages?

Answer 11

Macrophages digest most of the microorganisms except the antigen. They “regurgitate” these antigens (In) displaying them on their surface (antigen presenting cells) so that other wbcs called lymphocytes can take over the attack. There are two types: T and B cells.

Question 12

What are antigens?

Answer 12

Each antibody is specific for its antigen- no cross protection. We have millions of different antibodies. When B cells come into contact with their matching antigen, they are stimulated to divide into larger cells called plasma cells, which secrete huge amounts of antibodies.

Question 13

What are the functions of antibodies?

Answer 13

These antibodies circulate and attack the microorganisms that have not yet infected cells. Antibodies gather on the micro-organism’s surface. This blocks adhesion/ cell entry of the antigen. Neutralises and prevents organism’s replication. Signals (cytokines) macrophages and other wbcs to come. Kills organism via complement proteins -lysis. Neutralises toxin. Good of vaccines is to stimulate this response.

Question 14

When does the primary immune response develop?

Answer 14

Develops in the weeks following first exposure to an antigen

Question 15

When does the secondary immune response develop?

Answer 15

It is faster than the primary immune response and more powerful.

Question 16

What are memory cells?

Answer 16

After the body has eliminated the infection some of the B and T cells are converted into memory cells. These can quickly divide into the specialised B and T cells if re-exposure to the infection occurs. The immune systems capacity to have a memory of previous encounters with an infection is the basis for vaccination.

Question 17

How do vaccines work?

Answer 17

Induce active immunity. Immunity and immunologic memory similar to natural infection but without risk of disease. Immunological memory allows rapid recognition and response to infection. Prevents or modifies effects of disease.

Question 18

What is the immune response to an ideal vaccine?

Answer 18

Vaccine is taken up by antigen-preventing cells. Activates both T and B cells to give memory cells. Generates Th and Tc cells to the antigens. Antigen persists to continue to recruit B memory cells and produce high affinity antibody.