Cells of the adaptive immune response

Question 1

Which cells give rise to the cells of the adaptive immune system?

Answer 1

Self-renewing multipotent haemaotpoietic stem cells

Question 2

Which developmental pathway leads to the development of the cells of the adaptive immune system?

Answer 2

Lymphoid developmental pathway

Question 3

What are the two features of the adaptive immunity?

Answer 3

Shows immunological memory

Highly antigen specific

Question 4

What are the two types of lymphocytes?

Answer 4

B cells

T cells

Question 5

Features of B cells

Answer 5

Differentiate further into plasma cells

Release antibodies

Develop in the bone marrow directly from the common lymphoid progenitor

Question 6

Features of T cells

Answer 6

Stem cells leave the bone marrow and travel via the blood to the thymus to differentiate into T cells

Question 7

How can we distinguish between B and T cells

Answer 7

Via cell markers

Question 8

What are the T cell markers?

Answer 8

TCR - for antigen and MHC, recognises antigen

CD3 - all cells, interact with TCR and send intracellular signals upon activation

CD4/8 - once the T cells have matured

Question 9

What do CD4 T cells interact with?

Answer 9

MHC II

Question 10

What do CD8 T cells interact with?

Answer 10

MHC I

Question 11

What are the B cell markers?

Answer 11

BCR - B cell receptor for antigen, transmembrane version of antibody

IgA and IgB - similar to CD3 on T cells

CD19

Question 12

How can cell markers be useful?

Answer 12

Help differentiate between cells in a tumour - if cancer expresses CD19 on its surface = B-cell derived

Look for immunodeficiencies

Question 13

Specificity of lymphocytes

Answer 13

Lymphocytes are specific

One lymphocyte per antigen

Since there are so many antigens = antigen-specific lymphocyte number is low at first

Not enough present to eliminate the pathogen

To overcome the problem, once lymphocytes are activated by specific antigen they

Proliferate - enough cells to fend off infection and memory cell created

Question 14

What are the two types of TCR present on T cells?

Answer 14

Alpha beta TCR

Gamma delta TCR

Question 15

What is TCR type is more common?

Answer 15

Alpha beta TCR

Question 16

What is the role of alpha beta TCRs?

Answer 16

Better understood than gamma delta

Recognise processed antigens in form of peptide on MHC

Question 17

Which T cell types contain alpha beta TCRs?

Answer 17

Helper

Regulatory

Cytotoxic

Question 18

What is the role of the gamma delta TCRs?

Answer 18

Directly bind to antigens

Kill infected or stressed cells

Involved in immune regulation

Recognise lipids present on CD1

Question 19

What is the role of the CD4/8 surface molecules?

Answer 19

Establishes bond between TCR and MHC

Binds to MHC non-poplymorphic parts

Question 20

Which cell types drive differentation of T cells?

Answer 20

Dendritic cells

Question 21

What is the name of a T cell that has not differentiated yet?

Answer 21

Th0 cells

Question 22

Process by which dendritic cells activate T cells

Answer 22

DC use TOLL like receptors to recognise PAMPs

DCs can determine whether a pathogen is gram positive or gram negative

In response to what PAMPs bind, dendritic cells will

Change expression of molecules on CSM
Produce different concentrations of cytokines

Question 23

What types of cells do Th0 cells become upon activation with cytokines?

Answer 23

Th1 - cell mediated immunity, help CTT and macrophages

Th2 - humoral immunity, help the production of cytokines, help B cells in the production of antibodies

Question 24

What is the relationship between Th1 and Th2 cells?

Answer 24

Can inhibit each other

By production of cytokines

Question 25

What is the relationship between Th1 cells and macrophages?

Answer 25

Macrophages interact with Th1 cells to activate them Th1 cells interact with macrophages to stimulate them Bidirectional stimulation

Question 26

How do macrophages activate Th1 cells?

Answer 26

Via the release of cytokines like IL-12 Via cell-to-cell contact using CD40 receptors -> CD40 on macrophages interact with CD40L on Th1 cells Peptide presentation via MHC on macrophages binds to TCR on Th1

Question 27

How do Th1 cells stimulate macrophages?

Answer 27

Release of cytokines like gamma interferon

Question 28

What is the role of cytotoxic T cells?

Answer 28

Kills virus-infected and unhealthy cells by inducing apoptosis

Question 29

How do cytotoxic cells recognise target cells?

Answer 29

TCR binds to peptide sequences on MHC I

Question 30

What are the two mechanisms by which CTT cells destory target cells?

Answer 30

Fas/ Fas ligand mechanism Granzyme perforin mechanism

Question 31

Describe the Fas/Fas ligand mechanism

Answer 31

Fas is expressed on CSM of infected cells Fas Ligand is expressed on CD8 T cells Fas molecule releases apoptotic signal on binding with Fas ligand

Question 32

Describe the Granzyme perforin mechanism

Answer 32

Perforin molecules made by CD 8+ T cells produce pores on the surface of infected cells Granzymes insert into the cell through these pores and set up state of apoptosis

Question 33

How does apoptosis affect cells?

Answer 33

Causes membrane alterations in infected cells that are recognised by phagocytic cells

Question 34

How do B cells recognise antigens?

Answer 34

Recognise antigen directly B cells can be helped in seeing the antigen by follicular dendritic cells DC have Fc and complement receptors that allows to bind to immune complexes of antigen and antibody DC shows antigen in these immune complexes to the BCR - not essential, but enhances

Question 35

What features in B cells allows them to make lots of antibodies?

Answer 35

Contain lots of RER

Question 36

What is the difference in antigen presentation by MHC I and MHC II molecules?

Answer 36

MHC I - express enodgenous antigens. Assembly and presentation of peptides (8-10 a.a) MHC II - express exogenous antigens. Assembly and presentation of peptides (15 a.a)

Question 37

How do MHC I molecules present endogenous antigens?

Answer 37

Proteasome break down proteins of antigen and form peptides MHC molecules are made in the ER Proteasome is made in the cytoplasm Joining the two together via TAP1 and TAP2 MHC I and peptides transported through the trans-Golgi vesicle to the CSM

Question 38

How doe TAP proteins work?

Answer 38

Transporters associated with antigen processing Form pores in the membrane of the ER and take up peptides from the cytoplasm

Question 39

Describe the process of exogenous antigen presentation by MHC II

Answer 39

Molecules/ proteins or whole organisms are taken up from outside the cell Via phagocytosis or endocytosis Molecules end up in endosomes - contain proteolytic enzymes that break down proteins MHC II taken into vacuole which fuse with the endosome containing the antigen

Question 40

In what form is MHC II present in the vacuoles?

Answer 40

MHC II is bound to an invariant chain that stops it from binding to peptides in the ER When vaculoles with the MHC bind with the endosome containing the antigen, the invariant chain is removed to except a small residue called CHIP which remains on MHC II Antigen replaces CLIP and fuses with cell membrane

Question 41

What is the name of MHC in humans?

Answer 41

HLA

Question 42

Which HLA molecules are found on cells of the body?

Answer 42

HLA-A, -B, -C

Question 43

Which HLA molecules are found on cells of the immune system?

Answer 43

HLA-DP, -DQ, -DR