Abbas chapter 1

Question 1

What are the principle components of the innate immune system?

Answer 1

1) Physical & chemical barriers (e.g epithelia, anti-microbial chemicals produced at epithelial surfaces).
2) Phagocytic cells (i.e neutrophils & macrophages).
3) Blood proteins; including complement system & other mediators of inflammation.
4) Cytokines; which regulate & coordinate many activities of cells of innate immunity.

Question 2

Define antigens (modern)

Answer 2

Substances that bind to specific lymphocyte receptors,
whether or not they stimulate immune responses.

Question 3

What are the two types of adaptive immune responses

Answer 3

Humoral & cell mediated immunity.

Question 4

What is humoral immunity mediated by?

Answer 4

Antibodies in the blood & mucosal secretions.

Question 5

What cells involved in humoral immunity produce antibodies?

Answer 5

B lymphocytes (B cells).

Question 6

How do antibodies work?

Answer 6

They recognise microbial antigens, neutralise the infectivitity & target microbes for elimination by various effector mechanisms (e.g phagocytosis).

Question 7

How are antibodies transported into the lumen of mucosal organs & through the placenta?

Answer 7

Active transport.

Question 8

What cells mediate cell mediated immunity?

Answer 8

T-lymphocytes (T-cells).

Question 9

What is active immunity?

Answer 9

Immunity that is induced by exposure to a foreign antigen.

Question 10

What is passive immunity? Give an example.

Answer 10

Process where by the patient becomes immune to the particular antigen without ever being exposed due to receiving serum or lymphocytes from an exposed/immunised individual e.g tetanus antitoxin or anti-venom for snake bites or transfer of maternal antibodies.

Question 11

What are immunogens?

Answer 11

Substances that stimulate immune responses.

Question 12

What is opsonization?

Answer 12

Coating of pathogens with antibodies in order to increase their susceptibility to ingestion by phagocytes

Question 13

What parts of an antigen are specifically recognised by individual lymphocytes?

Answer 13

The determinants or epitopes.

Question 14

What does the lymphocyte repertoire refer to?

Answer 14

The total number of antigenic specificities of the
lymphocytes in an individual.

Question 15

What are the cardinal features of the adaptive immune system?

Answer 15

1) Specificity.
2) Diversity.
3) Memory.
4) Clonal expansion.
5) Specialisation.
6) Contraction & homeostasis.
7) Non-reactivity to self.

Question 16

What is clonal expansion? How is it beneficial?

Answer 16

An increase in the number of cells that express identical
receptors for the antigen.
Helps to fight off rapidly dividing pathogens.

Question 17

What is the benefit of immunological memory? Give specific examples.

Answer 17

Enhanced ability to respond again to the antigen; second & subsequent exposures are often more rapid, larger & qualitatively different from the 1st or primary immune response to the antigen. E.g Memory B cells produce antibodies that bind antigens with higher affinities on repeat exposure. Memory T cells react much quicker and more vigorously to antigen challenge vs naive T-cells.

Question 18

How do non-memory lymphocytes die after an immune response?

Answer 18

Apoptosis.

Question 19

What is immunological unresponsiveness also called?

Answer 19

Tolerance.

Question 20

What type of B lymphocyte secretes antibodies?

Answer 20

Plasma cells.

Question 21

Can T lymphocytes respond to soluble antigens? Why/ why not.

Answer 21

No. T cells recognise peptides derived from foreign proteins that are bound to host proteins (major histocompatibility complex molecules) which are expressed on surfaces of other cells.

Question 22

What do helper T-cells secrete? How does this help?

Answer 22

Cytokines.
Stimulates the proliferation & differentiation of T-cells, activate other cells including B cells, macrophages & other leukocytes.

Question 23

What are cytokines?

Answer 23

Messenger molecules of the immune system.

Question 24

How do cytotoxic T-lymphocytes work?

Answer 24

Kill cells containing foreign antigens (i.e viruses or intracellular pathogens).

Question 25

Name 3 classes of lymphocytes.

Answer 25

1) B cells.
2) T cells.
3) Natural killer cells.

Question 26

How can classes of lymphocytes be distinguished?

Answer 26

By expression of surface proteins called CD molecules (numbered).

Question 27

What is the role of antigen-presenting cells?

Answer 27

To capture & present an antigen to specific lymphocytes.

Question 28

What are the most specialised APCs?

Answer 28

Dendritic cells.

Question 29

Give some examples of effector cells.

Answer 29

Activated T cells, mononuclear phagocytes & other leucocytes.

Question 30

Why is cytokine synthesis transient?

Answer 30

Synthesis is initiated by new gene transcription as a result of cellular activation, the transcriptional activation is transient & the messenger RNAs encoding most cytokines are unstable & often rapidly degraded.

Question 31

Do cytokines have?
1) Autocrine function (act on the cell that they are produced by).
2) Paracrine function (act on a near by cell).
3) Endocrine function (act at a site distant to production).

Answer 31

All three.

Question 32

What role does IL-2 have in the immune response?

Answer 32

IL-2 is a growth factor that acts on the antigen-activated lymphocytes and stimulates their proliferation (clonal expansion)

Question 33

What is IL-2 produced by?

Answer 33

CD4+ helper T cells