MCP 35: Lymphoid II Flashcards
central lymphoid system
thymus and bone marrow
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
encapsulated
organ completely surround by connective tissue,
encapsulated organs
permanent i.e. lymph nodes, spleen
unencapsulted organs
transitory, MALT houses 85% of lymphatic tissue
lymph node ecotaxis, B-cells
superficial cortex and medulla
lymph node ecotaxis, T-cells
paracortex
blood ecotaxis, B-cells
low
lymph ecotaxis, B-cells
low
mucosal tissue ecotaxis, B-cells
high
spleen ecotaxis, T-cells
PALS
blood ecotaxis, T-cells
high
lymph ecotaxis, T-cells
high
muscosal tissue ecotaxis, T-cells
low
ecotaxis
lymphoid cells hone to certain areas based on cell receptor signals
circulating lymphocyte
have large nuclei, T-cell most common type of circulating lymphoid cell
diffuse lymphoid tissue
lymphocytes migrante to various locations within the mucosal tissue, i.e. the GI track, secretes IgA, most likely B-cells
major lymphoid tissues
circulating lymphocytes, diffuse lymphoid tissue, solitary nodules, aggregated nodules, specific organs
MALT
muscosa-associated lymphatic tissue, can be single cells, clusters of cells, or aggregation of cells
IgA
secreted from muscosa, prevents pathogen from invading mucosa
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
