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Infection, immunity and repair > Cells of the adaptive immune response > Flashcards

Cells of the adaptive immune response Flashcards

1
Q

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

A

Self-renewing multipotent haemaotpoietic stem cells

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2
Q

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

A

Lymphoid developmental pathway

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3
Q

What are the two features of the adaptive immunity?

A

Shows immunological memory

Highly antigen specific

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4
Q

What are the two types of lymphocytes?

A

B cells

T cells

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5
Q

Features of B cells

A

Differentiate further into plasma cells

Release antibodies

Develop in the bone marrow directly from the common lymphoid progenitor

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6
Q

Features of T cells

A

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

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7
Q

How can we distinguish between B and T cells

A

Via cell markers

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8
Q

What are the T cell markers?

A

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

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9
Q

What do CD4 T cells interact with?

A

MHC II

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10
Q

What do CD8 T cells interact with?

A

MHC I

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11
Q

What are the B cell markers?

A

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

IgA and IgB - similar to CD3 on T cells

CD19

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12
Q

How can cell markers be useful?

A

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

Look for immunodeficiencies

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13
Q

Specificity of lymphocytes

A

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

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14
Q

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

A

Alpha beta TCR

Gamma delta TCR

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15
Q

What is TCR type is more common?

A

Alpha beta TCR

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16
Q

What is the role of alpha beta TCRs?

A

Better understood than gamma delta

Recognise processed antigens in form of peptide on MHC

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17
Q

Which T cell types contain alpha beta TCRs?

A

Helper

Regulatory

Cytotoxic

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18
Q

What is the role of the gamma delta TCRs?

A

Directly bind to antigens

Kill infected or stressed cells

Involved in immune regulation

Recognise lipids present on CD1

19
Q

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

A

Establishes bond between TCR and MHC

Binds to MHC non-poplymorphic parts

20
Q

Which cell types drive differentation of T cells?

A

Dendritic cells

21
Q

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

A

Th0 cells

22
Q

Process by which dendritic cells activate T cells

A

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

23
Q

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

A

Th1 - cell mediated immunity, help CTT and macrophages

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

24
Q

What is the relationship between Th1 and Th2 cells?

A

Can inhibit each other

By production of cytokines

25
Q

What is the relationship between Th1 cells and macrophages?

A

Macrophages interact with Th1 cells to activate them

Th1 cells interact with macrophages to stimulate them

Bidirectional stimulation

26
Q

How do macrophages activate Th1 cells?

A

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

27
Q

How do Th1 cells stimulate macrophages?

A

Release of cytokines like gamma interferon

28
Q

What is the role of cytotoxic T cells?

A

Kills virus-infected and unhealthy cells by inducing apoptosis

29
Q

How do cytotoxic cells recognise target cells?

A

TCR binds to peptide sequences on MHC I

30
Q

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

A

Fas/ Fas ligand mechanism

Granzyme perforin mechanism

31
Q

Describe the Fas/Fas ligand mechanism

A

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

32
Q

Describe the Granzyme perforin mechanism

A

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

33
Q

How does apoptosis affect cells?

A

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

34
Q

How do B cells recognise antigens?

A

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

35
Q

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

A

Contain lots of RER

36
Q

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

A

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)

37
Q

How do MHC I molecules present endogenous antigens?

A

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

38
Q

How doe TAP proteins work?

A

Transporters associated with antigen processing

Form pores in the membrane of the ER and take up peptides from the cytoplasm

39
Q

Describe the process of exogenous antigen presentation by MHC II

A

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

40
Q

In what form is MHC II present in the vacuoles?

A

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

41
Q

What is the name of MHC in humans?

A

HLA

42
Q

Which HLA molecules are found on cells of the body?

A

HLA-A, -B, -C

43
Q

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

A

HLA-DP, -DQ, -DR

Infection, immunity and repair (52 decks)

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