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IBI Test 1 > B3.008 T Cell Activation > Flashcards

B3.008 T Cell Activation Flashcards

1
Q

4 main classes of pathogens`

A

bacteria
viruses
fungi
parasites

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2
Q

primary functions of T lymphocytes

A

production of cytokines
cytotoxicity
control of other immune cells

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3
Q

primary function of B lymphocytes

A

production of antibodies by plasma cells

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4
Q

what are 4 components of the acquired immune response, not necessarily exhibited by innate immunity?

A

specificity - lymphocyte responses are specific for antigens
diversity - immune system is able to produce a number of different responses
memory - lymphocytes respond anamnestically to antigens, memory is long lived
self/non self discrimination

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5
Q

how does a secondary immune response compare to a primary immune response?

A

secondary response is faster, bigger, and more specific

i.e. double the antibodies generated in half of the time

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6
Q

what is the physical structure of a T cell receptor?

A

heterodimer usually consisting of an a and b chain

sometimes gamma and delta chain

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7
Q

what is the physical structure of a B cell receptor?

A

consists of a cluster of molecules involving surface immunoglobulin (IgM or IgD)
coupled with disulfide bonded heterodimers (Ig-a and Ig-b)

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8
Q

where do T cells mature?

A

thymus

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9
Q

what are the 2 components of a T cell?

A

TCR (T cell receptor)

CD3 complex of molecules

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10
Q

what are the two major subgroups of T cells?

A

CD4+ (TH, T helper)

CD8+ (Tc, cytotoxic capabilities)

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11
Q

what are the 4 subtypes of CD4+ T cells

A

Th1
Th2
Th17
Treg

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12
Q

what is the function of Th1 cells?

A

cell mediated immunity
produce IFN-gamma and TNF-a (type 4 hypersensitivity)
respond to intracellular pathogens (viruses and some bacteria)

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13
Q

what is the function of Th2 cells?

A

humoral (blood) immunity
produce IL-4,5,13 (type 1 hypersensitivity)
helminths, allergic reactions, extracellular pathogens

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14
Q

what is the function of Th17 cells?

A

produce IL-17
acts upon a number of cell types
important in defense against extracellular bacteria and fungi

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15
Q

what is the function of Treg cells?

A

can suppress/inhibit the effector functions of CD4 and CD8 T cells
make up 5-10% of CD4+ cells
express CD25 and FOXP3

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16
Q

what other types of cells are stimulated by Th1?

A

macrophages

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17
Q

what other types of cells are stimulated by Th2?

A

B cells

mast cells

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18
Q

what is meant by cross regulation of Th1 and Th2?

A

the cytokines produced by each type inhibits the production of the other type
i.e. IFN-gamma produced by Th1 inhibits the Th2 response

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19
Q

what enhances Tc (CD8+)activation?

A

Th1 cytokines

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20
Q

what is required for killing by Tc (CD8+) cells?

A

direct contact and conjugate formation

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21
Q

what are the two pathways of Tc cells?

A

1: cytoplasmic granules = perforin + granzymes > apoptosis
2: Fas-Fas ligand interactions > apoptosis

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22
Q

what is Fas?

A

a programmed cell death indicator

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23
Q

what types of cells are antigen presenting cells?

A

B cells
macrophages
dendritic cells

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24
Q

what is the function of an antigen presenting cells?

A

enzymatically process antigen
present digested fragments to Th cells
do this using MHC class 2 molecules

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25
Q

what is an epitope?

A

part of an antigen recognized by the lymphocyte receptor

small part of the actual antigen

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26
Q

which types of cells can recognize epitopes in isolation?

A

B cells

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27
Q

which cells require MHC to present an epitope?

A

T cells

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28
Q

what is MHC?

A

major histocompatibility complex
found on chromosome 6
controls T cells function as they cannot act in isolation

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29
Q

what are the 4 types of surface molecules responsible for antigen recognition?

A

B cell receptor
T cell receptor
MHC class 1
MHC class 2

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30
Q

where are MHC class 1 molecules found?

A

all cells

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31
Q

what types of cells do MHC class 1 present to?

A

CD8+ T cells

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32
Q

where are MHC class 2 molecules found?

A

only antigen presenting cells

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33
Q

what types of cells do MHC class 2 present to?

A

CD4+ T cells

34
Q

what are the 3 components of an MHC class 1 molecules?

A

HLA-A
HLA-B
HLA-C
HLA= human leukocyte antigen

35
Q

what are the 3 components of an MHC class 2 molecules?

A

HLA-DP
HLA-DQ
HLA-DR

36
Q

what is the physical structure of an MHC class 1 molecule?

A

polymorphic heavy chain (a chain)

non-polymorphic light chain (B-2 macroglobulin) (not encoded within the MHC)

37
Q

what types of antigens do MHC class 1 present?

A

endogenous

antigen formed inside a host cell (viruses, tumors)

38
Q

what is the physical structure of an MHC class 2 molecule?

A

polymorphic a and b chains

both encoded within the MHC

39
Q

what types of antigens do MHC class 2 present?

A

exogenous antigen

originate outside of presenting cells (bacteria, vaccines, viruses caught between cells)

40
Q

describe the process of clonal selection

A

each lymphocyte coming into contact with specific antigen will be stimulated (becomes activated and proliferates)
clones of cells that are specific for the particular antigen will be made (larger population)
proliferation will take place at the expense of non-stimulated cells

41
Q

what are the two types of lymphocytes that can form from clonal selection?

A 
effector cells (majority)
-T cells
-plasma cells for B cells
memory cells (fewer)
-can be re-stimulated at a later date
42
Q

what are the different types of lymphoid tissue?

A

primary: thymus (T) and bone marrow (B)
secondary: lymph nodes and tissues
tertiary: the remaining areas where lymphoid cells are found

43
Q

describe the structure and function of the thymus

A

bilobed organ lying over the heart
contains T lymphocytes at various stages of development
committed T cells pass through the thymus where they undergo a selection process

44
Q

describe the function of the bone marrow

A

site of lymphocyte origin
T and B cells both begin their existence here
T cells leave undeveloped for the thymus cells mature and undergo selection to remove potential autoreactive cells

45
Q

what happens to foreign antigens which enter connective tissue?

A

carried by lymphatics to the nearest lymph node (draining lymph node)

46
Q

how is lymph moved?

A

along vessels by contraction of the bodies’ muscles in a one way system

47
Q

what would be the cause and result of lymph movement stopping?

A

lack of effective muscle contraction causes movement of lymph to cease
can cause edema in tissues
-legs and ankles swell after long journeys
-elephantiasis

48
Q

where does antigen presentation take place?

A

lymph nodes

49
Q

that are the 3 primary sections of the lymph node?

A

cortex
paracortex
medulla

50
Q

what is located in the cortex of the lymph node?

A

mainly B cells in germinal centers

  • primary follicles when resting
  • secondary follicles when activated and dividing
51
Q

what is located in the paracortex of the lymph node?

A

mainly Th cells

52
Q

what is located in the medulla of the lymph node?

A

plasma cells

53
Q

where are macrophages and dendritic cells found within the lymph node?

A

cortex and paracortex

54
Q

describe the structure and function of the spleen

A

largest lymphoid organ
hilum containing the splenic artery and vein
no lymphatic vessels supplying this organ
plays a significant role in immune response to blood borne diseases
site of removal of damaged RBC and platelets

55
Q

what are some other significant areas of lymphoid tissue throughout the body?

A

appendix
tonsils
adenoids
Peyer’s patches

56
Q

gut associated lymphoid tissues (GALT)

A

appendix

Peyer’s patches

57
Q

bronchial-associated lymphoid tissue (BALT)

A

similar system of tissues within the respiratory tract

58
Q

GALT + BALT =

A

MALT

mucosal-associated lymphoid tissue

59
Q

what types of cells transport antigens from mucosal surfaces to the lymphoid system?

A

microfold
membranous cells
referred to as M cells

60
Q

describe the 3 steps in lymphocyte recirculation

A
  1. lymphocytes leave the blood and enter the lymphatic system at lymph nodes
  2. leave through venous system through specialized epithelial cells (high endothelial venules (HEV)) by diapedesis or extravasation
  3. re-enter the venous circulation via the thoracic duct which enters the left subclavian vein
61
Q

what type of cells are part of the skin’s immune system?

A

Langerhans cells - dendritic cell of the cutaneous surface

62
Q

intraepidermal lymphocytes

A

TCR gamma delta cells that are thought to be first response to infection

63
Q

what is the definition of an antigen?

A

any molecule recognized by a BCR or TCR

64
Q

what are haptens?

A

small molecules that by themselves cannot induce an immune response
antigens but not immunogenic
induce an immune response when attached to a larger protein (nickel, penicillin, poison ivy)

65
Q

what is required by most isolated antigens to induce an immune response?

A

adjuvant

not all foreign proteins stimulate an immune response for this reason

66
Q

what are adjuvants

A

third party compounds or substances which stimulate the immune system

67
Q

what are some common functions of adjuvants

A

some non-specifically stimulate lymphocytes
some prolong antigen persistence
some induce receptors on accessory cells

68
Q

what happens if an antigen contains many epitopes?

A

some more dominant than others

immunodominant

69
Q

properties of T cell epitopes

A 
much better defined than those of B cells
8-11 AAs for MHC class 1
13-17 AAs for MHC class 2
must interact with both MHC and TCR at the same time
70
Q

what are 3 classes of T cell surface molecules?

A

CD40L
CD28
CTLA-4

71
Q

describe CD40L

A 
interacts with CD40 on APC
important for antibody class switching
lack of it leads to hyper IgM syndrome
72
Q

describe CD28

A

interacts with B7.1 (CD80) and B7.2 (CD86) on APC
important in providing a second signal to activated naïve T cells
lack of interaction can lead to anergy (lack of immune response)

73
Q

describe CTLA-4

A

constitutively expressed on Tregs and induced on activated T cells
interacts with B7.1 and B7.2
acts to switch off T cell function

74
Q

describe the chains of the TCR in more detail

A

both anchored in cell membrane

consist of a V (variable) and C (constant) region

75
Q

describe the process of generation of lymphocyte diversity

A

various V regions are encoded in a series of separate gene segments
when a functional gene is made, the appropriate gene segments are brought together in a unique physical rearrangement
prior to rearrangement, genes are in a germ line configuration
rearrangement called somatic recombination

76
Q

other than gene rearrangement, what can contribute to antigen receptor diversity?

A

slight changes in DNA
induced during the cutting and splicing or gene segments
changes nucleotide sequence by the addition of extra nucleotides into the joints between gene segments

77
Q

what is somatic hypermutation?

A

occurs in B cells (not T cells)

additional nucleotide substitutions take place during activation and division of cells

78
Q

what do B cells require to function?

A

T cells

79
Q

what do T cells require to function?

A

APCs to present antigen to them

80
Q

what is hematopoiesis?

A

production of cells from bone marrow

81
Q

what are the 2 primary genes which help regulate hematopoiesis?

A

BCL2 - inhibits apoptosis

Fas- when it interacts with FasL, apoptosis occurs

IBI Test 1 (15 decks)

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