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unit 7 Flashcards

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1
Q

what are the primary lymphoid organs?

A

thymus, bone marrow, GALT

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2
Q

what are the secondary lymphoid organs?

A

lymph nodes and spleen

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3
Q

what happens in the thymus?

A

T cell differentiation

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4
Q

what is a special feature of the thymus?

A

antigen independent proliferation

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5
Q

how does the thymus develop into a lymphoid organ?

A

multipotent lymphoid stem cells enter into the epithelial rudiment and occupy spaces between the epithelial cells

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6
Q

thymus structure

A

thin capsule made of connective tissues
trabeculae extend from capsule into parenchyma and establish thymus lobules

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7
Q

what part of the thymus contains developing T lymphocytes?

A

thymic cortex which is the outer portion of the thymic parenchyma

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8
Q

how will a stain appear when there is a large number of lymphocytes?

A

very basophilic

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9
Q

what do epithelioreticular cells provide?

A

a frame work for developing T lymphocytes

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10
Q

what types of epithelioreticular cells are found in the cortex?

A

I, II, and III

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11
Q

what types of epithelioreticular cells are found in the medulla?

A

IV, V, and VI

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12
Q

what is the major component of the blood-thymus barrier? what is it impermeable to?

A

endothelium
macromolecules

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13
Q

how do type I epithelioreticular cells protect T lymphocytes?

A

contain occluding junctions
surround the capillary wall in the cortex with their basal lamina

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14
Q

where is the perivascular CT contained? what does it do?

A

between the basal lamina of both epithelioreticular cells and endothelial cells
provides protection for developing T lymphocytes

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15
Q

thymic T cell education

A

a process of multipotential lymphoid stem cell maturation and differentiation into immunocompetent T cells

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16
Q

what is positive selection?

A

selection for thymocytes that recognize self MHC molecules expressed on cortical epithelium

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17
Q

what happens if the lymphocyte does not recognize self MHC and self antigen?

A

death of the cell

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18
Q

what happens to cells that pass positive selection?

A

they leave the cortex and enter the medulla and undergo another selection

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19
Q

where does positive selection occur? where does negative selection occur?

A

cortex of thymus
medulla of thymus

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20
Q

expression of what molecules occurs in positive selection?

A

CD2, CD7, CD1, TCRs, CD3, CD4, CD8

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21
Q

what cells present self antigen to developing T cells in positive selection?

A

type II and III epithelioreticular cells

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22
Q

what is negative selection?

A

selection against thymocytes that recognize self antigen in the context of self MHC

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23
Q

what cells are eliminated by negative selection?

A

T cells that demonstrate too high of an affinity for self MHC

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24
Q

cells that survive negative selection become what?

A

either cytotoxic CD8+ or helper CD4+ T lymphocytes

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25
what can help promote the negative selection process?
regulatory cytokines secreted by type VI epithelioreticular cells
26
what are thymic corpuscles derived from?
type VI epithelioreticular cells aka Hassall's corpuscles
27
thymic corpuscle characteristics
found in thymic medulla contain closely packed, concentrically arranged type VI cells exhibit flattened nuclei
28
what do thymic corpuscles contain? what is their probable function?
contain keratohyalin granules, bundles of cytoplasmic intermediate filaments, lipid droplets thought to produce interleukins that function in T differentiation and education
29
what results in the formation of different leukocytes and their precursors
interactions between bone marrow stromal cells, ECM components, cytokines, and developing hematopoietic cells
30
where are stromal cells that are involved in B cell development located?
endosteal surface (surrounds the medulla of bone marrow)
31
B cell development steps
stem cell pro-b cell pre-b cell b cell plasma cell (at some point, recognize antigen epitope to become a plasma cell)
32
what is the lymph node the main site of?
T and B lymphocytes antigen-dependent proliferation and differentiation into effector cells and memory cells
33
what are the parts of the lymph node?
capsule, cortex, medulla
34
what is the capsule of the lymph node composed of?
dense CT that surrounds the node
35
what is the sub capsular sinus of lymph node? what occurs here?
under capsule, adjacent to trabeculae afferent lymphatic vessels empty here they communicate with medullary sinuses
36
where do plasma cells not secrete antibodies?
in germinal centers
37
what does the parenchyma of a lymph node contain?
naive and antigen exposed T and B lymphocytes and accessory cells arranged in a reticular framework
38
what are lymphatic nodules/primary follicles?
spherical shaped aggregates of lymphocytes in the lymph node cortex
39
what occurs in a germinal center?
B cell proliferation and differentiation in response to an antigen
40
what is contained in the medulla of lymph nodes?
medullary cords and sinuses
41
what does the deep cortex of lymph nodes contain?
high endothelial venues consisting of cuboidal endothelial cells T cells
42
what is contained with primary nodules of lymph nodes?
naive B cells
43
what do medullary cords contain
lymphocytes, macrophages, dendritic cells, plasma cells
44
what are cells of the reticular meshwork
reticular cells, dendritic cells, macrophages, follicular dendritic cells
45
what do reticular cells do?
secrete type III collagen cytoplasmic processes wrap around bundles of reticular fibers provide supports express surface molecules and produce substance that attract T and B cells and dendritic cells
46
what do dendritic cells do?
express high levels of MHC and co-stimulatory molecules involved in antigen presentation
47
what do macrophages do?
phagocytosis antigen-presenting cells, express MHC I and II and costimulatory molecules
48
what do follicular dendritic cells do?
have thin, hair like branching cytoplasmic processes that interdigitate between B lymphocytes in the germinal centers
49
what do high endothelial venules contain?
receptors for antigen primed lymphocytes
50
what do high endothelial venules do?
signal lymphocytes to leave circulation and migrate into lymph nodes
51
how do lymphocytes enter the lymph node
through afferent lymphatic vessels
52
how do lymphocytes exit the lymph node
through efferent lymphatic vessels
53
how do lymphocytes from the blood enter the deep cortex?
high endothelial venules
54
what is lymphadenopathy?
abnormal enlargement of lymph nodes that undergo hypertrophy
55
what are some general features of the spleen?
derived from mesenchyme in the dorsal mesogastrium temporarily an organ for hematopoiesis embryonically it is a major repository for mononuclear phagocytic cells filters the blood
56
structural features of the spleen
surrounded by a CT capsule capsule trabeculae project into the substance of the spleen consists of red and white pulp
57
what are periarteriolar lymphatic sheaths? what kind of cells are typically found here?
a portion of white pulp that surround the splenic artery T lymphocytes are predominantly contained here
58
what is the red pulp?
consists of splenic sinuses surrounded by splenic cords contains large number of RBCs that it filters
59
open splenic circulation
splenic artery --> trabecular arteries --> central arteries --> penicillar arterioles --> reticular meshwork of splenic cords surrounding splenic sinus
60
what are the immune functions of the spleen?
antigen presentation initiation of immune response activation and proliferation of B and T cells production of antibodies removal of macromolecular antigens from the blood
61
what is splenomegaly?
enlargement of the spleen, commonly caused by portal hypertensions
62
histologic features of splenomegaly
thick and fibrotic capsule red pulp shows venous sinusoids and increased macrophage numbers white pulp is atrophic
63
which tonsils form a ring of lymphoid tissue in the entrance of the oropharynx?
pharyngeal tonsil, palatine tonsils, lingual tonsil
64
what are tonsils crypts?
epithelium forming the surface on the tonsils dips into underlying CT
65
what happens in tonsilar crypts?
many lymphatic nodules are evident in the walls of the crypt IgA antibodies are secreted from plasma cells that differentiate here
66
where are Peyer's patches found? what do they consist of?
the ileum numerous aggregations of lymphatic nodules containing T and B cells
67
where do Peyer's patches originate?
in the lamina propria, extend into the submucosa of the ileum they have specialized epithelium containing M cells that are involved in antigen presentation
68
what is unique about the lamina propria in the appendix?
heavily infiltrated with lymphocytes, contains numerous lymphocytic nodules
69
what are mucosal associated lymphoid tissues?
lymphoid tissue associated with the mucous membrane, not enclosed by a capsule
70
what do type I interfeurons have?
critical anti-viral and immunostimulatory effects they are produced within a few hours after viral infection
71
what cells can produce type I interferon?
almost any cells
72
what are plasmacytoid dendritic cells?
specialized interferon-producing cells

histology (15 decks)

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