4 th June 2024 Exam

Question 1

The innate immune system constitutes the first line of defence against pathogens. In order to
sense intruders, innate immune cells are equipped with different types of pattern recognition
receptors (PRR).

a) Give a brief overview of the most important innate immune receptor classes and their
general function. (2p)

Answer 1

Toll like receptors are located on the membrane and endosomes and can recognise LPS, viral RNA, flagellin etc.
Nod like receptors are cytosolic and some such as the NLRP3 can activate the inflammasome that activates caspase-1 to produce pro-inflammatory cytokines such as IL-1b.
Rig like receptors recognize viral RNA and by interferon inhibits viral reproduction.
C-type lectin receptors are membrane bound and recognize fungal and bacterial carbohydrates and causes phagocytosis and inflammation.
Phagocytic receptors recognize opsonized pathogens and intituate phagocytosis. Examples of phagocytic receptors are Fc receptors and complement receptors.

Question 2

The innate immune system constitutes the first line of defence against pathogens. In order to
sense intruders, innate immune cells are equipped with different types of pattern recognition
receptors (PRR).

Mention four mechanisms for limiting innate immune responses, i.e., how innate
immunity is “turned off” after an immune response.

Answer 2

1. Antiinflammatory cytokines such as IL-10 and TGF-B are produced by macrophages and Tregs and inhibit immune cell activation and promote tissue repair.
2. Molecules such as A20 and SOCS proteins inhibit downstream signalling of PRRs which dampens cytokine production.
3. The clearance of PAMPs and DAMPs by phagocytosis causes the immune activation to reduce.
4. Certain innate immune cells undergo apoptosis such as neutrophils after clearing infection and macrophages phagocyte them.

Question 3

T helper (Th) cells are polarized by cytokines, and act by secreting cytokines that will lead to
activation and recruitment of other effector cells. Read all sub-questions before you start to
write your answers.
a. Mention for each inflammatory subset (Th1, Th2, Th17) the differentiation-inducing
cytokines, i.e. the cytokines that induce polarization of a naïve Th cell into a Th1, Th2
or Th17 cell. (1.5p)

Answer 3

Th1 secrete IFNg and activated macrophages.

Th2 produces IL-4,5,13 and activates eosinophils

Th17 produces IL-17,22 and activates neutrophils.

Question 4

T helper (Th) cells are polarized by cytokines, and act by secreting cytokines that will lead to
activation and recruitment of other effector cells. Mention for one subset (Th1 or Th2 or Th17) one cytokine that is typically secreted
and give examples on two effector cells that are typically affected by this cytokine.

Answer 4

Th1 cells secrete IFN-g and activates macrophages which kills intracellular pathogens and cytotxic

Question 5

T helper (Th) cells are polarized by cytokines, and act by secreting cytokines that will lead to
activation and recruitment of other effector cells.Explain briefly how each subset (Th1, Th2, Th17) leads to elimination of different
classes of pathogens.

Question 6

T helper (Th) cells are polarized by cytokines, and act by secreting cytokines that will lead to
activation and recruitment of other effector cells. RFor one of the three Th subsets, give one example of a cytokine that would be
beneficial to block in a disease setting, and in which disease.