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Histology - Exam 3 > Lymphoid System - Part 1 > Flashcards

Lymphoid System - Part 1 Flashcards

1
Q

central lymphoid organs?

A
  • bone marrow

- thymus

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2
Q

what is bone marrow a source of?

A

stem cells

-B cells derived from stem cells reside in non-thymic lymphoid organs

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3
Q

what is thymus a source of?

A

stem cells from bone marrow mature to T cells here

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4
Q

where are B cells derived from?

A

bone marrow lymphoid progenitor cells

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5
Q

describe differentiation of B cells

A

interaction w/ T helper/macrophages results in clonal expansion and antibody producing plasma cells and memory B cells (important in secondary antibody response)

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6
Q

what do B cells recognize?

A

free antigen peptides not bound to MHC complex

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7
Q

what do T cells recognize?

A

respond to cell-bound antigens

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8
Q

T helper cells

A
  • CD4+
  • interact w/ B cell/macrophage to stimulate response to foreign antigen
  • recognize MHC II on antigen presenting cells
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9
Q

two subclasses of T helper cells

A
  • Th1: important in response to viral and bacterial infection
  • Th2: important in response to parasitic infection
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10
Q

T cytolytic/cytotoxic cells

A
  • CD8+

- recognize MHCI on antigen-presenting cells

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11
Q

where do NK cells come from?

A

bone marrow cell -> null cell (large, granular lymphocyte)-> NK cell

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12
Q

what does a null cell lack?

A
  • T cell receptor (TCR)

- CD4 and CD8 co-receptors

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13
Q

do NK cells require interaction with an antigen-presenting cell to be activated?

A

no - part of innate immune system

-recognize virus infected cells and cancer cells

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14
Q

how can NK cells participate in adaptive immune response?

A

by participating in antibody-dependent cell mediated cytotoxicity (ADCC) - will recognize antibody on a pathogen infected cell and lyse cell

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15
Q

function of antigen presenting cells

A

surveillance cells - internalize antigens by phagocytosis and break them down to peptide fragments which are bound to MHC molecules -> peptide-MHC complex exposed on surface for presentation to T cells

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16
Q

2 types of MHC and which cells have each?

A

MHC I: all nucleated cells

MHC II: antigen presenting cells, endothelial cells, thymic epithelial reticular cells

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17
Q

name other cells (from different locations) that are antigen presenting cells

A
  • cells in macrophage lineage
  • Kupffer cells (liver)
  • Langerhans cells (skin)
  • dendritic cells (peripheral lymphoid organs)
  • glial cells in CNS
  • fibroblasts
  • mast cells
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18
Q

peripheral lymphoid organs

A
  • spleen
  • lymph nodes/nodules
  • tonsils
  • appendix
  • peyer’s patches (ileum)
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19
Q

subepithelial/diffuse lymphoid tissue

A
  • lymphocytes free in loose CT
  • diffuse infiltration in intestinal and respiratory tract, part of genitourinary system
  • may be lymphoid nodules
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20
Q

capsules of lymphoid nodules

A

don’t have one

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21
Q

where/how can you find lymphoid nodules?

A
  • may be in subepithelium

- solitary or aggregated (peyer’s patches)

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22
Q

composition of lymph nodes

A

dense lymphatic tissue surrounded by dense irregular CT capsule w/ trabeculae through node that converge on hilus

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23
Q

lymph node hilus

A

region where lymph exits node via efferent lymphatic vessels - arteries/veins also enter/leave node here

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24
Q

what constitutes stroma of node?

A

capsule and trabeculae + network of reticular fibers and cells

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25
Q

how are sinuses separated from capsule, trabeculae and dense lymphoid tissue?

A

by squamous endothelial cells + reticular cells + fixed macrophages attached to reticular fiber network

26
Q

what antigen presenting cells are found in lymph node cortex?

A

large follicular dendritic cells (FDC)

27
Q

types of lymphoid nodules in outer cortex of node

A
  • primary - unstimulated (no germinal center)

- secondary - germinal center present

28
Q

what do germinal centers contain?

A
  • larger lymphoblasts

- marginal zone of smaller lymphocytes and some macrophages around periphery

29
Q

when do germinal centers occur in lymphoid nodules?

A

when B cells activated by helper T cells undergo clonal expansion (lymphoblasts) towards becoming an antibody secreting plasma cell

30
Q

describe the selection process that occurs w/ maturing B cell lymphoblasts

A

mature cells contact FDCs, which present antigens to them: -those w/ low affinity antibodies undergo apoptosis and are phagocytosed by macrophages
-cells w/ high affinity antibodies move to medullary cords and become plasma cells

31
Q

what type of cells accumulate in mantle zone of lymphoid follicle?

A

cells that are non-specific for antigens presented by FDC

32
Q

which parts of lymph nodes are primarily B cells and which are primarily T cells?

A

B cells: nodules and medullary cords

T cells: paranodular and inner cortex regions

33
Q

medullary cords have high numbers of which cells?

A

plasma cells

34
Q

segregation of B and T cells w/i nodules is based on what?

A

various cytokine signals

35
Q

what empties into a subcapsular sinus and where are these located?

A

subcapsular sinus = b/w capsule and outer cortex

multiple afferent lymphatic vessels empty into it

36
Q

where does lymph flow from subcapsular sinus?

A

into intermediate/trabecular sinuses that run along trabeculae -> medullary sinuses around medullary cords

37
Q

importance of high endothelial venules

A

important route of lymphocyte migration (selectins on lymphocyte membrane aids recognition of HEV) - most lymphocytes enter node via this route

38
Q

where are high endothelial venules found?

A

in paracortical zone

39
Q

lining of high endothelial venules

A

tall cuboidal endothelial cells

40
Q

pathway of lymphatic flow from origination back to venous system

A
  1. thymus -> T cells and bone marrow -> B cells into blood circulation
  2. migration through high endothelial venules into lymph node
  3. move into lymph node tissues and/or circulate out into lymphatic circulation
  4. return to blood via main thoracic duct
41
Q

which cells recirculate into venous circulation?

A
  • primarily T cells

- some B cells recirculate, but more stay in tissues compared to T’s

42
Q

three tonsils?

A
  • lingual
  • pharyngeal
  • palatine
43
Q

lingual tonsils

A

diffuse infiltration of lymphocytes or multiple small nodules below epithelium of the posterior third of tongue

44
Q

pharyngeal tonsils

A

adenoids

-posterior wall of nasopharynx

45
Q

pharyngeal tonsil epithelium

A

covered w/ ciliated pseudostratified columnar epithelium - some portions may be stratified squamous (especially in old folks)

46
Q

palatine tonsils

A

b/w glossopalatine and pharyngopalatine arches

47
Q

palatine tonsil epithelium

A

stratified squamous epithelium - HAS DEEP CRYPTS (invaginations down into parenchyma)

48
Q

capsule of palatine tonsil?

A

base and sides enclosed in dense CT capsule

49
Q

peyer’s patches

A

aggregated nodules of lymphoid tissue located primarily in lower ileum

50
Q

segregation of B and T cells in peyer’s patches

A

similar to lymph nodes:

  • nodules mainly B cells
  • paranodular area mainly T cells
51
Q

what does the follicular epithelium of peyer’s patches contain?

A

M cells

52
Q

appendix lamina propria

A

extremely rich in diffusely scattered lymphoid elements and solitary nodules

53
Q

lymphadenitis

A

excessive immune response to infectious agents that results in proliferation of cells and edema in nodes - also causes inflammation

54
Q

what are lymph nodes a common site of, clinically?

A

metastasis of cancer cells

55
Q

why are lymphoid cells the source of various types of lymphoma?

A

b/c of the frequent, rapid division and differentiation of lymphoid cells

56
Q

what is the primary mediator of graft rejection and GVHD?

A

T cells - by MHC antigens on cells

57
Q

what does it mean when a graft is rejected?

A

patient’s immune system sees graft as foreign and attacks it

58
Q

what does it mean when you have graft vs. host?

A

T cells in a graft can see the host as foreign and attack the host

59
Q

in what procedure is GVHD a problem?

A

bone marrow transplants

60
Q

can you still get GVHD even when MHC antigens are matched up in a transplant? why or why not?

A

yes - due to minor histocompatibility antigens

61
Q

two examples of minor histocompatibility antigen mismatches

A
  1. H-Y- antigen present in male but not female tissue

2. HA-2 antigen associated w/ myosin

Histology - Exam 3 (12 decks)

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