MCP 35: Lymphoid II Flashcards by Gregory McWilliams

central lymphoid system

thymus and bone marrow

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peripheral lymphoid system

after T and B cells mature in bone marrow and thymus, they travel through blood and lodge in a part of the peripheral lymphoid system

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encapsulated

organ completely surround by connective tissue,

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encapsulated organs

permanent i.e. lymph nodes, spleen

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unencapsulted organs

transitory, MALT houses 85% of lymphatic tissue

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lymph node ecotaxis, B-cells

superficial cortex and medulla

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lymph node ecotaxis, T-cells

paracortex

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blood ecotaxis, B-cells

low

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lymph ecotaxis, B-cells

low

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mucosal tissue ecotaxis, B-cells

high

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spleen ecotaxis, T-cells

PALS

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blood ecotaxis, T-cells

high

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lymph ecotaxis, T-cells

high

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muscosal tissue ecotaxis, T-cells

low

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ecotaxis

lymphoid cells hone to certain areas based on cell receptor signals

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circulating lymphocyte

have large nuclei, T-cell most common type of circulating lymphoid cell

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diffuse lymphoid tissue

lymphocytes migrante to various locations within the mucosal tissue, i.e. the GI track, secretes IgA, most likely B-cells

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major lymphoid tissues

circulating lymphocytes, diffuse lymphoid tissue, solitary nodules, aggregated nodules, specific organs

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MALT

muscosa-associated lymphatic tissue, can be single cells, clusters of cells, or aggregation of cells

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IgA

secreted from muscosa, prevents pathogen from invading mucosa

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mechanism for IgA secretion

pathogen stimulates B-cell into plasma cells and produces IgA, secreted as dimer with secretory pieces from epithelia to protect from being degraded during transcytosis

solitary nodules

aggregation of single lymphocytes and diffuse lymphatic tissue in response to local infection, occur in MALT and lymph nodes, not encapsulated, transitory

secondary nodules

dark outer mantle and lighter staining germinal center,

lymph nodes

filter the lymph

spleen

filters the blood

aggregated nodules

semi permanent, not fully encapsulated, grow and recede due to the presence of antigens; tonsils, Payer's patches, vermiform appendix,

Peyer's patches

aggregated nodule--in ilium of small intestine, M-cells (micro fold cells) facilitate direct interaction between pathogen and macrophage

germinal center of solitary node

light in color because lymphocytes have transformed into plasma cells and have more cytoplasm; mantle hosts inactive lymphocytes

vermiform appendix

aggregated nodule--can rupture in young people but less of an issue in older people because immune system declines, located at the McBurney’s point

thymus

T-cells mature here, capsulated, light staining medulla and darker staining cortex (contain T-cells and blood thymus barrier), Hassall's corpuscles, thymus blood barrier, looses immune function with age

Hassall's corpuscles

distinguishing characteristic of thymus, epithelial reticular cells

trabeculae of thymus

canals that divide lobes into different regions

T-cell maturation in thymus

stem cells from bone marrow enter the cortex and move toward medulla, inefficient process, 95% of T-cells end up being recognized as "self" and are destroyed

lymph nodes

can be used as a marker for cancer methastosis, to see if it spreads

epithelial reticular cells

scaffold on which T-cells mature, sometime they die and form a ball called Hassall's corpuscles

flow through lymph nodes

afferent lympahtic, subscapular sinus, trabeucular sinus, medullary sinus, exits through efferent lymphatics. Blood enters through the hillium into paracortical region (efferent lymphatics).

lymph node cortex

contains B-cells and antigen presenting cells

lymph node paracortical/deep cortext area

T-cells and antigen presenting cells here

functions of spleen

1.) filters blood 2.) reservoir for platelet storage, 3.) destroys RBCs 4.) can participate in hematopoises if needed

post capillary high endothelial venues (HEV)

main way for lymphocytes entering blood to go into lymph node; lined by cuboidal epithelium cells, lymphocytes can cross the HEVs to end up in the parenchyma of the lymph node where they interact with pathogens, in paracortical area

red pulp of spleen

concentrated RBCs

white pulp of spleen

concentrated WBCs,

flow of blood through spleen

systemia arterial supply, central artery,

central artery

surrounded by white pulp, some blood flows into the periphery in the marginal zone

periarteriolar lymphatic sheaths (PALS)

collection of T-cells that monitor blood antigen content that surround the central artery, this is surrounded by a layer of B-cells

marginal zone sinuses

ring of sinuses that the blood flows through at the periphery

splenic sinusoids

do not let RBCs pass that are old

open circulation

slow, accounts for 90%

closed circulation

fast, accounts for 10%

tonsils

partially encapsulated, part not encapsulated is surrounded by stratified squamous non keratinized epithelium

positive and negative selection in thymus

Positive Selection: recognize self MHCs | Negative selection: recognize foreign Ag