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
how are sinuses separated from capsule, trabeculae and dense lymphoid tissue?
by squamous endothelial cells + reticular cells + fixed macrophages attached to reticular fiber network
26
what antigen presenting cells are found in lymph node cortex?
large follicular dendritic cells (FDC)
27
types of lymphoid nodules in outer cortex of node
- primary - unstimulated (no germinal center) | - secondary - germinal center present
28
what do germinal centers contain?
- larger lymphoblasts | - marginal zone of smaller lymphocytes and some macrophages around periphery
29
when do germinal centers occur in lymphoid nodules?
when B cells activated by helper T cells undergo clonal expansion (lymphoblasts) towards becoming an antibody secreting plasma cell
30
describe the selection process that occurs w/ maturing B cell lymphoblasts
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
what type of cells accumulate in mantle zone of lymphoid follicle?
cells that are non-specific for antigens presented by FDC
32
which parts of lymph nodes are primarily B cells and which are primarily T cells?
B cells: nodules and medullary cords | T cells: paranodular and inner cortex regions
33
medullary cords have high numbers of which cells?
plasma cells
34
segregation of B and T cells w/i nodules is based on what?
various cytokine signals
35
what empties into a subcapsular sinus and where are these located?
subcapsular sinus = b/w capsule and outer cortex multiple afferent lymphatic vessels empty into it
36
where does lymph flow from subcapsular sinus?
into intermediate/trabecular sinuses that run along trabeculae -> medullary sinuses around medullary cords
37
importance of high endothelial venules
important route of lymphocyte migration (selectins on lymphocyte membrane aids recognition of HEV) - most lymphocytes enter node via this route
38
where are high endothelial venules found?
in paracortical zone
39
lining of high endothelial venules
tall cuboidal endothelial cells
40
pathway of lymphatic flow from origination back to venous system
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
which cells recirculate into venous circulation?
- primarily T cells | - some B cells recirculate, but more stay in tissues compared to T's
42
three tonsils?
- lingual - pharyngeal - palatine
43
lingual tonsils
diffuse infiltration of lymphocytes or multiple small nodules below epithelium of the posterior third of tongue
44
pharyngeal tonsils
adenoids | -posterior wall of nasopharynx
45
pharyngeal tonsil epithelium
covered w/ ciliated pseudostratified columnar epithelium - some portions may be stratified squamous (especially in old folks)
46
palatine tonsils
b/w glossopalatine and pharyngopalatine arches
47
palatine tonsil epithelium
stratified squamous epithelium - HAS DEEP CRYPTS (invaginations down into parenchyma)
48
capsule of palatine tonsil?
base and sides enclosed in dense CT capsule
49
peyer's patches
aggregated nodules of lymphoid tissue located primarily in lower ileum
50
segregation of B and T cells in peyer's patches
similar to lymph nodes: - nodules mainly B cells - paranodular area mainly T cells
51
what does the follicular epithelium of peyer's patches contain?
M cells
52
appendix lamina propria
extremely rich in diffusely scattered lymphoid elements and solitary nodules
53
lymphadenitis
excessive immune response to infectious agents that results in proliferation of cells and edema in nodes - also causes inflammation
54
what are lymph nodes a common site of, clinically?
metastasis of cancer cells
55
why are lymphoid cells the source of various types of lymphoma?
b/c of the frequent, rapid division and differentiation of lymphoid cells
56
what is the primary mediator of graft rejection and GVHD?
T cells - by MHC antigens on cells
57
what does it mean when a graft is rejected?
patient's immune system sees graft as foreign and attacks it
58
what does it mean when you have graft vs. host?
T cells in a graft can see the host as foreign and attack the host
59
in what procedure is GVHD a problem?
bone marrow transplants
60
can you still get GVHD even when MHC antigens are matched up in a transplant? why or why not?
yes - due to minor histocompatibility antigens
61
two examples of minor histocompatibility antigen mismatches
1. H-Y- antigen present in male but not female tissue | 2. HA-2 antigen associated w/ myosin