Examples of questions for Cellular Immunology

Examples of questions for Cellular Immunology/Cellular Biology and Immunology

Each student gets a set of 6 questions, so that each set contains different types of questions

and that the set of questions covers different chapters of the main lectures (there are no

specific questions on the case studies).

At the start of the exam, you draw a set of 4 questions for which you get 30 min. written

preparation. During the oral exam, the answer to these 4 questions is discussed. You also

get 2 additional questions to be directly answered orally. These last 2 questions count for 5

out of 20 marks on the exam.

Examples of the 4+2 questions (and the corresponding answer) can be found below

(P.S. The full set of 6 questions below is not included in the exam, but some of you

may randomly draw a set containing one or a few of the questions below)

1) What are the main types of helper T cells? How do these differ in terms of their

main immunological functions and in the defining cytokines and transcription

factors involved in their induction and function? (5/20)

Th1

Priming and amplifying cytokines: IL-12, IFN-g

Polarizing transcription factor: T-bet (induced by IFN-g)

Unique cytokine products: IFN-g

Main functions: signaling via IFN-g and CD40L induces cellular immunity against

intracellular pathogens, by acting on cells of cellular immunity:

o macrophage activation

o CD8

CTL activation

o class switching in B cells, resulting in opsonizing antibodies (that can interact with

Fcg receptors on macrophages)

Th2

Priming and amplifying cytokines: IL-25, IL-4

Polarizing transcription factor: GATA-3 (induced by IL-4)

Unique cytokine products: IL-4, IL-13, IL-5, IL-10

Main functions: signalling via Th2 cytokines and CD40L induces humoral immunity

against extracellular pathogens, by inducing class switching in B cells, resulting in

neutralizing antibodies and IgE antibodies interacting with Fce receptors on eosinophils

Th17

Priming and amplifying cytokines: TGFb, IL-6, IL-23

Polarizing transcription factor: RORgT (induced by TGFb + IL-6)

Unique cytokine products: IL-17A, IL-17F, IL-21, IL-22

Main functions: antimicrobial activity against extracellular bacteria at epithelial surfaces.

Hereto, the Th17 cytokines act on epithelial, endothelial, stromal cells. These activated

epithelial, endothelial, stromal cells will:

o secrete antimicrobial peptides such a b-defensins

o secrete inflammatory cytokines and recruit neutrophils

2) What are the main stages of B cell development and activation in the spleen?

How is this affected by T-cell help? (5/20)

Interaction between T helper cells and follicular B

cells (dependent on antigen presentation by the B

cells on MHCII and on CD40L and cytokine signals

from the Th cell) is needed for the germinal centre

reaction, allowing:

o Class switching (from IgM to IgA/G/E)

o Somatic hypermutation (-> allowing affinity

maturation of the antibodies, since the B cells that randomly generate the highest

affinity antibodies will be able to most effectively take up the antigen through the

B cell receptor (surface-bound antibody) and thus successfully compete with other

B cells for the T cell help)

3) Which stimuli can induce maturation and activation of dendritic cells? (2.5/20)

4) What is IL-2? By which cells is it expressed and by which stimuli is its

expression regulated? What are its main immunological functions? (2.5/20)

o Interleukin-2 = a cytokine

o secreted by effector T cells, when these are activated by signalling through the

TCR, recognizing peptides presented on MHC molecules.

IL-2 production by effector T cells is enhanced when the T cells also receive a

costimulatory signal, for example through B7 molecules expressed on antigen

presenting cells, binding to CD28 expressed on the T cells.

o main growth factor for T cells:

§ important for proliferation and activation of effector T cells in the

induction of immunity

§ critical for immune tolerance:

• by inducing activation-induced cell death in effector T cells

• as growth factor for Tregs (Tregs need IL-2, but do not secrete IL-2

themselves)

(Remark: the function of IL-2 as growth factor for effector T cells can be

partly compensated by other growth factors such as IL-7, but not its role in

tolerance induction. As a consequence, IL-2 deficient mice develop a

lethal lymphoproliferative disease, in which the control of T cell

proliferation is lost).

Examples of additional questions at the oral exam

5) In which cases can B cell mediated antibody responses be elicited in MHC class

II deficient individuals? Why? (2.5/20)

MHC class II is needed for positive selection of CD4+ helper T cells during thymic

development.

MHC class II is also needed for interaction between Thelper cells and follicular B cells in

germinal centres.

Thus, in MHC class II deficient individuals, there will be no helper T cells and no T cell

help for B cell development.

As a consequence, you will only get T-cell independent (thymus-independent) antibody

responses (by splenic Marginal Zone B-cells and peritoneal B-1 B cells). Two types of

thymus-independent (TI) B-cell activation can occur:

• TI type 1 activation is when a B cell binds to an antigen and receives secondary

activation by Toll-like receptors, leading to polyclonal B-cell activation or

specific Ab response

• TI type 2 activation when the antigen is a molecule with multiple repeating

subunits which can simultaneously cross link enough B cell receptors to fully

activate the B cell (e.g. Ficoll or repetitive polysaccharide antigens on

encapsulated bacteria)

6) Which method(s) could be used to study in vivo the role of granzyme B expressed

by regulatory T cells in limiting auto-immunity? (2.5/20)

If you study the development of autoimmunity in granzyme B deficient mice, all cells

(including for example effector CD8+ T cells) will lack granzme B, not only the Tregs.

You could isolate Tregs from granzyme B deficient mice and adoptively transfer them

into immunodeficient mice (for example athymic nude mice), together with adoptive

transfer of effector Tcells from wild-type mice but this may not be a very natural system.

To study the role of granzyme B expressed specifically by regulatory T cells, you could

use a Treg-specific granzyme B KO mouse, based on the Cre-Lox system.

Hereby, you need transgenic mice in which LoxP recombination sites are introduced in

the introns of the granzyme B gene. In these “floxed” mice, the LoxP sites will be spliced

out of the granzyme B mRNA, resulting in normal granzyme B expression in most cells.

However, in cells expressing cre recombinase, recombination of the granzyme B gene

will result in a non–functional mRNA.

In addition, you also need another transgenic mouse strain in which the cre recombinase

is expressed specifically in Tregs, which could for example be obtained by expressing the

cre under control of the Treg-specific FoxP3 promotor (for example introducing the cre

gene downstream of the FoxP3 coding region in the genome, with an internal ribosome

entry site in between, to allow expression of both FoxP and Cre protein from the same

mRNA that is under control of the FoxP3 promotor).

When breeding the FoxP3-Cre mice with the Granzyme B-LoxP mice, the resulting

offspring will contain mice in which Granzyme B is specifically inactivated in cells

expressing FoxP3 (i.e. Tregs) and is normal in other cells.