Morphology and function of lymphoid organs (ketchum) Flashcards
lymphoid system functions
monitor neutralize and destroy harmful agents
Thymic epithelial cell are what type of cells (functional or stromal)
functional and stromal
Reticular cells produce fibers with what type collagen
type III
Functional cells of lympoid system
lymphocytes, macrophages, APCs and TECs thymic epithelial cells
Does everyone have cancer
yes at some point but the immune system responds and kills cells before they can proliferate
2 primary cells in immune response
B lymphocytes- specific ab producing
T lymphocytes- T helper, cytotoxic cells, and regulatory
What type of lymphocytes are with humoral immunity and cellular immunity
B- humoral
T- cellular
maturation of lymphocytes occur in
bone marrow and thymus
Once lymphocytes mature where do they go
peripheral tissues or spleen or lymph node
what is the direct effect when the primary immune response is stimulated
cell proliferates (immunoblasts) to make clones to bind and kill
quiescent B cells
memory cells ready for secondary immune response or re exposure of Ag- rapid response
Instead of producing ab what to T cells do
produce antigen recognizing receptor
What is the actual name for a b lymphocyte producing ab
plasma cell. eccentric nucleus, clockface nucleus because of chromatin clumping.
perinuclear clear zone- golgi because exporting lots lots of protein.
very basophilic because ribosomes
how is our immune system so great if we only have 20 cells specific to each Ag
upon stimulation, cells proliferate
how do we organize the lymphoid system
collections in organs or tissues. un encapsulated and encapsulated
what is a Lymph nodule, is it encapsulated or not.
large collection of lymphocytes- un-encapsulated
Which are more active primary or secondary lymphocytes and what are their appearances
secondary are more active, have a pale center where lymphocytes are proliferating and differentiating
diffuse un encapsulated collections of lymphocytes indicates what
activity, infection in that area
Hyaline cartilage with cilia and globule cells is indicative of what
trachea
name of lymphocyte collection in the intestine
peyers patches- dark staining in mucosa of gut.
GALT
gut associated lymphoid tissue
Malt
mucus associate lymphoid tissue
Are tonsils encapsulated
not entirely, partially
Characteristics of palantine tonsil
large paired collections nodules
stratified squamous non keratinized epithelium
epithelial crypts to increase SA
characteristics of pharyngeal tonsil
pseudostratified columnar epithelium with cilia and globular because like respiratory tract
single crypts
ECM- collagen type III fibers
characteristics of lingual tonsils
no crypts. smaller more numerous nodules. huge salivary glands.
very similar to palantine minue crypts
What is the name for encapsulate lymph
lymph nodes
Where to the afferent lymphatics enter node. where do efferents exit
thru capsule enter
exit via hilum
paraenchyma divided into ?
cortex and medulla
Cortex components
sinues, nodules
diffuse lymphoid tissue
connective tissue trabeculae
Medulla components
medullary cords, sinuses and trabeculae
What is the architecture of the cortex
irregular sinuses. “subcapsular sinus” then move into cortical or paratrabecular sinuses
bathes all the lymphocytes and if lymphocyte recognizes anything in fluid, reaction
Where are B lymphocytes typically found in cortex? T lymphocytes?
B- nodular areas
T- non-nodular
Where to macrophages present Ag to lymphocytes
in germinal centers
Majority of cells in medullary cords
B cells and plasma
Trabeculae in medulla characterized by
anucelate, white appearance, high in collagen III and some I
Paracortex
not nodular. mostly T lymphocytes. inner to cortex layer.
When an Ag comes into lymph node what cells will they encounter first
B cells in node and then T cells in paracortex
blood vessels in lymph nodes used for?
trafficking. T cells enter and leave circulating in periphery but will return through specialized capillaries HEVs
HEVs
high endothelial venule- looser tight junctions to allow cells to diapedis in and out. to enter and exit blood.
What does the epithelial look like around HEVs
cuboidal, not like normal squamous
Functions of spleen
filters blood
salvages Fe from old RBCs
sire of generation of abs by plasma cells
reservoir of RBCs
site of erythropoiesis in fetus during 3rd/4th- 7th month
Structure of spleen
fibro-muscular capsule.
does not have afferent lymphatic. only efferent
arteries and veins (splenic vein formed by trabeculae veins)
Paraenchyma composition of spleen
no cortex or medulla but has red and white pulp
red pulp-RBCs
white pulp- WBCs
Structure of white pulp
vessels are surrounded by T lymphocytes. Periarterial lympoid sheath PALS
Structure of red pulp
blood vessels. filtration is happening. turnover of RBCs- hemocidrin- Fe being recovered by macrophages
plasma cells to produce ab
Describe splenic circulation
Open: capillaries dump right into red pulp, these RBCs have to get back into sinusoids so this is where we recycle RBCs that lyse as they try to migrate through capillaries
Closed: channel comes in and exits (artery arteriole capillary vein)
basic Artery spleen
splenic artery- trabecular arteries- penicillar arteries (pulp) branch into central arteries in white pulp that either go directly into sinus (closed) or into red pulp (open)
Is the thymus nodular
no, cortex and continuous medulla
What lymph cells are found in thymus
thymocytes to mature into T lymphocytes
What is the thymic stroma made of
thymic epithelial cells- they do not make fibers
more functional because secrete cytokines and present antigens
Vascular of thymus
enter cortico-medullary junction to where it branches into either cortex or medulla
What is the blood thymus barrier
sheathed by macrophages and thymic epithelial cells. They form nests for maturing thymocytes
teach T lymphocytes what to recognize. self vs nonself
Each capillary of blood thymus barrier is surround by what
endothelial cell lining it, a macrophage associated with it and a thymic epithelial cell to extend a process to wrap around it
Does thymus have afferent/efferent lymphatics
only efferent
Hassall’s corpuscles
no known function but how we characterize the medulla of thymus.
the corpuscles produce TSLP Thymic lymphopoietin
accumulate with time
TSLP
helps T cells mature. specifically T regulatory cell
Characterization of older thymus
adipocytes-clear areas
dense lymphocyte populations
a lot of stromal areas that have built up over time
“a trophic” still functional but not growing
Thymus involution
decreased lymphocytes and function over time, weaker immune system with age
how do T lymphocytes make it to thymus for maturation
CD44 when leave bone marrow
interacts with cytokines CCL21 and CCL25 to stick to thymus
Maturation of T lymphocytes in thymus
1) CD4, CD8 CD25 negative, CD44+ Double neg (DN1)
2) develop CD25 so now called (DN2)
3) lose CD44 = (DN3)
4) lose CD 25 = (DN4)
5) develop CD4 and CD8 (DP) double+
6) lose either CD4 or CD8 to become SP single+
Where in the thymus are DN4 lymphocytes found
cortex
Where in the thymus are DP lymphocytes found
cortico-medullary junction
Where in the thymus are the SP lymphocytes found
medulla to exit into circulation
What part of immune education occurs in the cortex of thymus
positive selection. immature T lymphocyte comes in contact with thymic epithelial cells. want to keep cells that recognize TEC, ability to communicate with self
What part of immune education occurs in medulla of thymus and at what stage are the lymphocytes?
DP lymphocytes. Negative selection, get rid of cells that recognize APCs(macrophages and dendritic cells) these APCs are presenting SELF antigens.
Describe B cell T-independence and T-cell dependence
T cell independence: B cells can be activated directly by bacterial toxins
T cell dependence: majority, helper T cells stimulate B cell proliferation and activation by secreting IL 4, 5 and 13
Mode of HIV on T cells
infect and inactivate helper T cells- enter by binding CD4 at cell surface.
