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Pathology > Cell mediated immunity (year 2) > Flashcards

Cell mediated immunity (year 2) Flashcards

1
Q

what is required for antibody to be produced?

A

T and B cells

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2
Q

if antibody can’t be produced what can this lead to?

A

higher mortality rates and great susceptibility to disease

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3
Q

what are T and B cells?

A

circular cells with T cell receptors (TCR) and B cell receptors (BCR) on them

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4
Q

what are the three main regions on the receptors?

A

constant, variable and transmembrane

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5
Q

what are the two forms of T cell receptors?

A

alpha/beta heterodimers

gamma/delta heterodimers

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6
Q

where are alpha/beta heterodimers found?

A

they are membrane bound and the classic MHC class I or II

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7
Q

where are gamma/delta heterodimers found?

A

these are non-membrane bound and bind to free specialised antigens - lots found in cattle

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8
Q

what letter do B cell receptors resemble and what is this structure similar to?

A

Y - an antigen

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9
Q

where does T cell selection occur?

A

in the thymus

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10
Q

what does MHC stand for?

A

major histocompatibility complex

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11
Q

describe the process of T cell selection

A

arrive as double negative - lack CD4/CD8
T cells get given both CD4 and CD8 surface markers so are now double positive
T cell then undergoes positive selection in response to whether they recognise MHC (the way antigen is presented)
they then undergo negative selection in response to whether they recognise self-proteins
finally move into the medulla where they become single positive for either CD4 or CD8

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12
Q

what does MHC do?

A

presents the antigen to a host T cell

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13
Q

how is MHC classified?

A

class I and II

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14
Q

which class of MHC does CD4+ T cells recognise?

A

class II

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15
Q

which class of MHC does CD8+ T cells recognise?

A

class I

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16
Q

on what cells in MHC class I expressed?

A

all nucleated cells except RBCs, platelets and nerve cells

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17
Q

what cells express MHC class II?

A

all professional antigen presenting cells

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18
Q

give examples of some professional antigen presenting cells (APCs)

A

dendritic cells
macrophages
B cells

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19
Q

MHC shows heterozygosity. what significancy does this have?

A

there is huge genetic diversity which can lead to disease resistance

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20
Q

where is the MHC complex assembles?

A

inside the cell, it is then transported to the surface where T cells can recognise the proteins

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21
Q

what determines if the antigen is presented as class I or II?

A

the route of entry

22
Q

what antigens are presented as as class I?

A

intracellular pathogens that directly enter the cytosol and undergo endogenous antigen processing

23
Q

what antigens are presented as class II?

A

extracellular pathogens that enter the cells via endocytosis or phagocytosis and undergo exogenous antigen processing

24
Q

describe the process of exogenous antigen processing

A 
extracellular pathogens enter the cell and are processed via the endocytic pathway, the peptides are then presented by MHC class II molecules
these are recognised by T cell receptors of CD4+ T helper lymphocytes and cytokines are secreted which enhances the humeral (antibody) and cellular immune responses
25
Q

describe the process of endogenous antigen processing

A

intracellular pathogens are processed via cytosol and proteasome and the resulting peptides are presented by MHC class I
these are recognised by T cell receptors of CD8+ T cytotoxic lymphocytes
cytokines are then secreted which enhances cell mediated immunity

26
Q

what are the 3 types of T cell?

A

cytotoxic CD8
T helper 1 CD4
T helper 2 CD4

27
Q

lymphocytes express thousands of identical receptors unique for what?

A

a single epitope

28
Q

cytotoxic T lymphocytes are restricted to which MHC class?

A

class I - they are CD8 positive

29
Q

what do cytotoxic T cells do?

A

kill cells that are infected with intracellular pathogens

30
Q

T-helper lymphocytes are restricted to which MHC class?

A

class II - they are CD4+

31
Q

what is the role of T-helper cell 1 (Th1)?

A

proinflammatory - activates cytotoxic T lymphocytes to kill intracellular pathogens

32
Q

what is the role of T-helper cell 2 (Th2)?

A

anti-inflammatory - stimulate antibody production and switching

33
Q

what is Th0?

A

an undifferentiated T helper cell

34
Q

what can Th0 differentiate into?

A

Th1, Th17 and Th2

35
Q

what drive Th0 differentiation?

A

cytokines

36
Q

what are cytokines?

A

soluble protein messengers of the immune system

37
Q

what T helper cells are involved in cell mediated immunity?

A

Th1 and Th17

38
Q

what factors dictate the type of cellular immune response?

A

type of pathogen (intra/extracellular)

cytokine microenvironment

39
Q

what is a cytokine microenvironment?

A

small localised part of a lymph node, spleen or intestine

40
Q

what microorganisms will cause Th0 to differentiate into Th1?

A

bacteria and viruses

41
Q

what microorganisms will cause Th0 to differentiate into Th1?

A

bacteria and fungi

42
Q

what microorganisms will cause Th0 to differentiate into Th2?

A

helminths, yeast, bacteria

43
Q

name the effectors released from CD8 cells

A 
IFN-gamma
TNF-beta
perforin
granzymes
fas ligand
44
Q

name the effectors released from Th1 cells

A 
IFN-gamme
IL-3
IL-2
TNF-alpha
TNF-beta
45
Q

name the effectors released from Th2 cells

A 
IL-4
IL-5
IL-10
IL-13
CD40-ligand
46
Q

Th1 and Th2 have antagonistic mechanisms, what are these?

A

Th1 - IFN-gamma antagonises Th2

Th2 - IL-4 and IL-13 antagonises Th1

47
Q

why is the antagonism of Th1 and Th2 a problem?

A

often with responses are needed to clear an infection so the first pathway that is triggered needs to be over come

48
Q

what happens once antigen is presented?

A

clonal expansion

49
Q

describe the process of clinical expansion

A

the single T/B cell proliferates
the cells enlarge and stop migrating
chromatin becomes less dense to allow protein synthesis
within a few hours lymphoblasts have formed
lymphoblasts give rise to 2-4 daughter cells each day producing memory lymphocytes and effector cells

50
Q

what cells need activation to survive and which don’t?

A

effector cells do

memory cells don’t

Pathology (17 decks)

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