Lecture 1

Question 1

What does the immune system do

Answer 1

• It provides defence against infection
  -Distinguishes between self and non-self
  -Can recognise the danger signals caused by damage to cells such as cancer, heart attack and stroke

Question 2

What is the immune system

Answer 2

It is an integrated system of organs, tissues, cells and cell products that differentiates self from non-self and neutralises pathogenic organisms or substances

Question 3

What is active immunisation

Answer 3

The induction of immunity after exposure to antigens. Antibodies are created by the recipient and are then stored permanently (memory cells)

Question 4

What is passive immunisation

Answer 4

The process in which individuals receive antibodies from another source rather than producing them on their own

Question 5

Who popularized variolation

Answer 5

Lady Mary Wortley Montagu after witnessing the practise in Turkey in the early 1720s

Question 6

What are the features of the innate immune system

Answer 6

• It is evolutionary ancient
  -It provides broad specificity (not-affected by prior contact)
  -Immediate/ rapid response
  -No memory component

Question 7

What are the features of the adaptive immune system

Answer 7

-Only recently evolved (500 million years ago/ only in vertebrates)
-It’s highly specific (recognises antigens)
-Can be enhanced by primary contact (has a memory component)
-It’s a slow response- days/ weeks

Question 8

What is an antigen

Answer 8

Any chemical, compound or structure foreign to the body that elicits an adaptive immune response

Question 9

What do adaptive and innate immunity both have

Answer 9

Leukocytes and soluble factors

Question 10

What does the innate immune system consist of

Answer 10

• Barriers: physical e.g. skin, chemical e.g. stomach acid (breaching barriers triggers MAMPs)
  -Soluble proteins: complement, interferons
  -Local and systematic responses: fever and inflammation
  -Leukocytes (phagocytes and NK cells)

Question 11

What is complement

Answer 11

They are innate immunity proteins that are produced by the liver, they circulate the blood where they form holes in bacterial membranes, killing bacteria.

Complement is composed of several soluble protein factors that are constantly present in the blood

Question 12

What does the adaptive immune system consist of

Answer 12

• B and T lymphocytes:
• B cells make antibodies and respond by secreting soluble antibodies (HUMORAL IMMUNITY)
• T cells develop into cytotoxic t cells (kill infected cells) or helper t cells (secrete cytokines that act on other cells) CELL MEDIATED IMMUNITY
• T and B cells develop into memory cell

Question 13

What do PMNs (granulocytes) include and what are they known for

Answer 13

Basophils, Eosinophils, neutrophils.

Known for their multilobed nuclei and enzyme rich lysosome organelles

Question 14

What do neutrophils do

Answer 14

They engulf microbes by phagocytosis and can undergo NETosis

Question 15

What can PAMPs include

Answer 15

LPS, peptidoglycan, anything found on pathogens that aren’t on host cells

Question 16

Receptors of the innate immune system

Answer 16

-Myeloid cells: provide broad specificity PRRs that recognise MAMPs
-NK cells recognise altered self cells

These types of cells are expressed by all leukocytes of a particular type and genes are inherited in the germline (don’t evolve quickly).
There are a limited number of PAMPs

Question 17

Receptors of the adaptive immune system

Answer 17

B and T cells have highly specific antigen receptors that recognise particular molecules.
- B cell receptors are the membrane form of an antibody
-T cell receptors are clonally expressed
Genes are expressed at random during lymphocyte development (there are 10^9 specificities)

Question 18

What did Macfarlane Burnett (1958) propose

Answer 18

The body can produce millions of B cells each with a different preformed receptor on his surface. Each recognising a particular microbe on a different pathogen

The clonal selection theory

Each B cell divides exponentially from the same parent. They differentiate each time resulting in lots of soluble antibody in the blood

Question 19

What are the dangers of the clonal selection hypothesis and what was the solution

Answer 19

Could result in antibodies that recognise bodies own molecules. So any lymphocytes that recognise self molecules are deleted early

Question 20

How does the innate system maximise host defence whilst minimizing damage to host tissues

Answer 20

-Small number of inherited PPRs recognise MAMPs unique to microbes
-They’re good at distinguishing between self and non-self
-There’s potential for collateral damage to self

Question 21

How does the adaptive system maximise host defence whilst minimizing damage to host tissues

Answer 21

-They cannot reliably distinguish between self and non-self or between harmful and innocuous material
- There is clonal activation- response is limited in that way
-They target immune response specifically towards infection (sparing uninfected tissues)

Question 22

What happens in primary lymphoid tissue

Answer 22

Immature lymphocytes made in bone marrow mature into antigen sensitive b cells and t cells

Question 23

What happens in secondary lymphoid tissue

Answer 23

Stations where lymphocytes can encounter antigens leading to the differentiation of B cells into antibody-secreting plasma cells and t cells into antigen specific helper cells

Question 24

Examples of secondary lymphoid tissue

Answer 24

Spleen (filters blood to detect microbes)
Lymph nodes (located at positions to trap microbes that drain from local tissues)