lymphocytes

Question 1

what type of immune cells are lymphocytes?

Answer 1

adaptive

Question 2

why do you need adpative immunity?

Answer 2

• only relatively easily evolved
• absence results in inability to clear infection
• protects from repeat infections
• not without costs- autoimmunity

Question 2

what are the functions of adaptive immunity

Answer 2

• improves efficiency of innat response
• focuses a response on site of infection and organism responsible
• has memory
• needs time to develop

Question 3

what does having immunonlogical memory mean?

Answer 3

• more rapid and heightened immune reactiion that serves to eliminate pathogens fast and prevent diseases
• reduction in severity on re-exposure
• antigen- specific lymphocytes
• basis for vaccines

Question 4

what are the roles of T cells

Answer 4

it is a cell mediated response
- produce cytokines to help shape immune response (CD4)
- kill infected cells (CD8)

Question 5

what is the role of B cells

Answer 5

it is a humoral response
- produce antibodies

Question 6

How do T and B cells recognise pathogens?

Answer 6

TCR and BCR

Question 7

What is an antigen?

Answer 7

molecules that act to induce an adaptive immune response

Question 8

epitope

Answer 8

the region of an antigen which the receptor binds to

Question 9

How do t cells recognise antigens in relation to epitopes?

Answer 9

T cells recognise linear epitopes in the contect of MHC

Question 10

how do B cells recognise antigens in relation to their epitopes?

Answer 10

antibodies recognise structural epitopes

Question 11

what is clonal selection?

Answer 11

the presence of foreign molecules and receptor

Question 12

What is clonal expansion?

Answer 12

Interaction between a foreign molecule and that receptor leads to activation and local expansion (multiple copies of the same cell)
Differentiated effector cells of that lineage will bear the same receptor

Question 13

What is the problem of antigen diversity?

Answer 13

-we exposed to an incredibly large amount of different microbes and other antigenic determinants- no predicting which no one’s
- immune system must be able to respond to them all
- but the adaptive immune system is exquitely specific
- to respond to all these different antigens, we need to have a very large pool of cells with specific receptors that can recognise these huge array of antigens

Question 14

How is antigen receptor diversity generated

Answer 14

Recombination

Question 15

When are functional genes for antigen receptors generated?

Answer 15

During lymphocyte development

Question 16

How are BCR receptor chains encoded

Answer 16

Each BCR receptor chains (kappa,lambda, and heavy chain genes) is encoded by separate multigene families on different chromosomes

Question 17

How does recombination occur?

Answer 17

During B cell maturation these gene segments are rearragngeed and brought together
The process is called immunoglobulin gene rearrangement

Question 18

Where is a T cell receptor found

Answer 18

T cell receptor is part of a complex of proteins on the cell surface

Question 19

How is the variable region on T cell receptor made?

Answer 19

Gene reassignment

Question 20

What does T cell receptors do?

Answer 20

Recognise antigen fragments presented by other cells in the context of MHC

Question 21

What does the major histocompatibility complex (MHC) do?

Answer 21

Plays a central role in defining self and non self
Presents antigens to T cells
Recognise linear

Question 22

MHC class I properties

Answer 22

all nucleated cells , although at various levels
Has single variable alpha chain plus a common beta-microglobulin
All molecules in body has this

Question 23

MHC Class II properties

Answer 23

Normally only present in ‘professional’ antigen presenting cells
Has 2 chains, alpha and beta

Question 24

What gene is MHC encoded by?

Answer 24

HLA

Question 25

How is the MHC polygenic

Answer 25

3 class I and class II loci

Question 26

What is the MHC gene expression

Answer 26

Co-dominant hence each person can have up to 6 of each gene if completely heterozygous. There are more than 170000 MHC variants

Question 28

What happens in intracellular MHC/TCR interactions

Answer 28

Processed in cytosol Presented in MHC I presented to CD8 T cells

Question 29

What happens on extracellular MHC/TCR interactions

Answer 29

Processed in endosomes Presented in MHCII Presneted on CD4 cells

Question 30

What are the two types of T cells and their functions

Answer 30

CD4 (helper) CD8 (killer)

Question 31

Do different pathogens all have the same strategy to kill them?

Answer 31

No

Question 32

What are the classes of CD4 T helper cells

Answer 32

T helper cells produce cytokines (a family of inflammatory mediators) Cytokines have diverse actions on a wide range of cells They influence the outcome of the immune response.

Question 33

what do CD8 (cytotoxic T lymphocytes) do?

Answer 33

- kill their targets by programmed cell death = apoptosis - apoptosis is charcterised by framentation of nuclear DNA - Cytotoxic T cell store perforin, granzymes, granulysin in cytotoxic granules released after traget recognition - perforin molecules polymerise, form pores.

Question 34

antibody structure

Answer 34

- variable region - constant region - heavy region - light region

Question 35

what is antibody function?

Answer 35

antobodies extremely important in protection against reinfection

Question 36

what are the three core protective roles for antibodies

Answer 36

- neutralisation - oposinisation - complement activation

Question 37

what are the different types of antobody classes

Answer 37

IgG- highest oposonisation and neutralisation activities (four types) IgM- produced first upon antigen invasio, increase transiently IgA- expressed in mucosal tissues, forms dimers after secretion IgD- unknown IgE- involved in allergy

Question 38

what are B cells?

Answer 38

- white blood cells - lymphocytes - effector cells of humoral immunity (secrete antobodies) - memory B cells (ready to prevent repeat infections)

Question 39

where of B cells cocme from

Answer 39

- generationa and maturation in the bone marrow - migrate in circulation (blood, lymphatic system) adn into lymphoid tissues - mature B cells are specific for a particular antigen - specificity resides in the B cell receptor (BCR) for antigen

Question 40

what is the BCR?

Answer 40

surface bound antibody, encodes the antibody the cell will make

Question 41

what are the properties of the BCR

Answer 41

- BCR have a unique binding site which bind to a portion of the antigen celled antigenic determinant or epitope - is made before the cell ever encounters antigen - is present in thousands of identical copies on the surface of the B lymphocyte

Question 42

What do B cells bind to?

Answer 42

soluble antigen

Question 43

what is the general rule for naive antigen specific lymphocytes (B or T)

Answer 43

They cannot be activaed by antigen alone

Question 44

Naive B cells require accesory signalling in what way?

Answer 44

1) directly from microbial constituents 2) from a T helper cell

Question 45

What is one way antibody production by B cells achived?

Answer 45

T helper cell thymus- dependent (all Ig-classes) (Memory)

Question 46

what is another way antibody production by B cells is achieved?

Answer 46

microbial constituent thymus-independent (Only IgM) (No memory)

Question 47

What do Thymus- independent antigens do?

Answer 47

- directly activate B cells without the help the help of T cells - often polysaccharide, needs to have a repetiitve structure, e.g. bacterial surface sugars - The second signal required is provided by a microbial PAMP, e.g. LPS

Question 48

What do thymus-dependant antigens do?

Answer 48

- the membrane bound BCR recognises antigen - the receptor-bound antigen is internalised and degraded intp peptides - peptides associate with 'self' molecules (MHC II) and expressed at the cell surface - this complex is recognised by macthed CD4 T helper cell - B cell activated

Question 49

What are the properties of CD8 (cytotoxic cells)

Answer 49

Cytotoxic cells kills their targets by programmed cell death apoptosis Apoptosis is characterised by fragmentation of nuclear DNA