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OPHTH Immunology > Immune cell and organs > Flashcards

Immune cell and organs Flashcards

1
Q

What is the function of secondary lymphoid organs?

A

Where lymphocytes can interact with antigen and with other lymphocytes, including spleen, LNs, MALT

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2
Q

In an embryo where does haematopoietic occur?

A

amniotic sac

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3
Q

In a fetus where does haematopoiesis occur?

A

all bones, liver + spleen

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4
Q

Where does haematopoiesis occur in adults? 5 sites

A
  1. Flat bones
  2. Vertebrae
  3. Iliac bones
  4. Ribs
  5. End of long limbs
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5
Q

What is the broad structure of the thymus?

A

bilobed, medulla + cortex regions

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6
Q

What is the role of the Hassalls’ corpuscle in the thymus?

A

secretes soluble factors + is important in regulatory T cells

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7
Q

Is there a change in the thymus during the immune response to antigens?

A

no - continuous development of T cells

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8
Q

What volume of lymph is returned to the blood each day + how?

A

2-3L of lymph, via superior vena cava

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9
Q

What is the size + shape of lymph nodes?

A

kidney shaped, >1cm

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10
Q

How does lymph enter + exit LNs?

A
  • enters via afferent vessel
  • exits via efferent
  • lymph percolates through all lymphocytes before leaving the node
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11
Q

What is meant by a lymph node being described as a summative junction?

A

there are many afferent vessels but one efferent vessel

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12
Q

What is meant by a lymph node being described as a summative junction?

A

there are many afferent vessels but one efferent vessel

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13
Q

How do lymphocytes enter the lymph nodes?

A

rich blood supply lets lymphocytes into the LNs via high endothelial venules

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14
Q

Which part of the lymph node is the T cell area?

A

parafollicular cortex

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15
Q

Which part of the lymph node is the B cell area?

A

lymphoid follicle - mostly on periphery of the lymph node

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16
Q

What leads to the generation of a germinal centre in a lymph node?

A

during immune response there is massive proliferation of B cells

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17
Q

What targets respective lymphocytes to their specific areas of the LN?

A

specific chemokines

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18
Q

What is a function of the spleen?

A

filter for antigens in the blood

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19
Q

What 2 regions is the spleen broadly split into?

A

white pulp + red pulp

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20
Q

What is the white pulp of the spleen?

A

lymphoid cells around blood vessels, full of lymphocytes

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20
Q

What is the white pulp of the spleen?

A

lymphoid cells around blood vessels, full of lymphocytes

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21
Q

What 3 areas is the white pulp of the spleen further divided into?

A
  1. Peri-arteriolar lymphatic sheath (PALS) = T cell area
  2. Splenic lymphoid follicles
  3. Marginal zone
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22
Q

Where are the B cell lymphocytes located in the spleen?

A

follicles

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23
Q

What may be contained within the follicles of the spleen?

A

germinal centres - form upon antigenic stimulation

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24
Q

What is the marginal zone of the spleen?

A

interface of red pulp with PALS and follicles

25
Q

What is the function of the marginal zone of the spleen?

A

contains macrophages, screens systemic circulation for antigens + pathogens, role in antigen processing

26
Q

Where does the gut-associated lymphoid tissue drain?

A

involved in mesenteric lymphatic drainage system to mesenteric LNs, including intraepithelial lymyphocytes

27
Q

What are the 2 components fo the gut-associated lymphoid tissue?

A
  1. Peyer’s patches
  2. M-cells
28
Q

What are Peyer’s patches formed of?

A

non-capsulated aggregation of lymphoid tissue - predominantly B lymphocytes and contain germinal centres during immune responses

29
Q

What is the function of M cells of the gut-associated lymphoid tissue?

A

sample contents of the intestine, surveying for pathogens which they can then deliver to immune cells

30
Q

Label the following on the GALT diagram: villus, crypt, M cell, Peyer’s patch.

A
31
Q

What are 3 types of immune cells within the epidermis of the skin?

A
  1. keratinocytes
  2. Langerhans cells
  3. Intraepidermal lymphocytes
32
Q

What are 2 types of immune cells present in the derm of the skin which heavily guard the epidermis?

A
  1. Macrophages
  2. T lymphocytes
33
Q

What structures exist within the dermis of the skin which assist with its immune function?

A

venules + lymphatic vessels - provides entry to the blood circulation + drainage to regional lymph node

34
Q

How does the body ensure that antigen meets lymphocyte with the specific receptor for it?

A

lymphocyte recirculation - pathogen is on mucosal surface, naive lymphocytes leave the bone marrow + thymus + enter bloodstream, reirculate through peripheral lymphoid tissue -> recognise antigen leading to massive B cell proliferation in secondary lymphoid tissue

35
Q

What happens to lymphocytes if they don’t recognise specific antigen?

A

die

36
Q

When does extravasation of naive T cells into the lymph nodes occur?

A

during the immune response

37
Q

What are 4 steps of the physical process of extravasation of a naive T cell into a lymph node?

A
  1. naive T cell rolls along epithelium
  2. stopped + activated by specific chemokines at a particular place on the epithelium - place it stops determined by selectins
  3. integrins increase adhesion of the T cell to the epithelium, leading to arrest of the cell
  4. transendothelial migration of T cell into LN occurs
38
Q

How do antigens enter lymph nodes?

A

via draining lymphatics

39
Q

What is the role of selectins in T cell extravasation into LNs?

A

stop the lymphocyte at a particular place on the epithelium

40
Q

What is the role of integrins in the extravasation of T cells into the LN?

A

increase adhesion of the T cell to the epithelium leading to cell arrest

41
Q

How many times do naive T cells circulate?

A

once per day

42
Q

How do T cell lymphocytes enter the lymph nodes?

A

high endothelial venule

43
Q

Where does the naive lymphocyte get activated by antigen?

A

within the lymph node after entering via high endothelial venule

44
Q

What happens after a lymphocyte is activated within a lymph node?

A

stops recirculating - massive proliferation of B lymphocytes - re-enter blood via SVC + target invading microbes/pathogens

45
Q

How many CD markers exist?

A

> 300

46
Q

What CD surface marker is expressed by all T lymphocytes?

A

CD3-antigen specific receptor (TCR)

47
Q

What are 2 types of TCR and their breakdown in terms of proportion of T lymphocytes in blood?

A
  • γδ TCR - 10%
  • αβ TCR - 90%
48
Q

What is the breakdown of αβ TCR expression cells in terms of which express CD4 and whcih CD8?

A
  • CD4: 2/3
  • CD8: 1/3
49
Q

What is the function of CD4+ cells?

A

T helper cells, regulatory T cells - secrete cytokines

50
Q

What is the function of CD8+ cells?

A

cytotoxic T cells - lyse infected cells, secrete cytokines

51
Q

What happens to ability to respond to new infections with age? What happens to the total number of T cells with age?

A
  • reduced ability to respond to new infections, as thymic output declines with age + thymus atrophies
  • total number of T cells doesn’t change - just more memory cells
52
Q

What is the only situation when T lymphocytes can recognise antigen?

A

using T cell receptor when antigen presented at surfce of another cell; antigen is presented by an MHC molecule

53
Q

What molecule is presented on a ll B lymphocytes? What is the function of this?

A

MHC class II - can present ntigen to helper T cells

54
Q

How can B lymphocytes recognise antigen?

A

intact antigen free in body fluids (so not presented by another molecule, unlike T cells)

55
Q

How can B lymphocytes recognise antigen?

A

intact antigen free in body fluids (so not presented by another molecule, unlike T cells)

56
Q

What forms the B cell receptor?

A

a membrane-anchored form of antibody linked to signalling subunits

57
Q

What are 4 types of APCs?

A
  1. dendritic cells
  2. B lymphocytes
  3. macrophages
  4. follicular dendritic cells
58
Q

Where are each of the key 4 types of APCs located?

A
  1. DCs: widely spread e.g. skin + mucosal tissue
  2. B cells: lymphoid tissue
  3. Macrophages: lymphoid tissue
  4. follicular dendritic cells: lymph node follicles
59
Q

What do each of the 4 types of APC present antigen to?

A
  1. DCs: T cells
  2. B cells: T cells
  3. Macrophages: T cells
  4. follicular dendritic cells: B cells

OPHTH Immunology (8 decks)

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