Secondary Lymphoid Organs Flashcards
Where do B cells mature?
Bone marrow
Where do B cells and T cells originate?
Bone marrow
Where do T cells migrate to mature?
Thymus
What are the secondary lymphoid organs?
Lymph nodes (500-600 in the body), spleen, and mucosal-associated lymphoid tissue (MALT)
Where does the recognition phase of the adaptive immune response occur?
In the secondary lymphoid organs (lymph nodes usually)
How do secondary lymphoid organs help lymphocytes survive and continue to recirculate even when they don’t find their cognate antigen?
By providing them with sustaining signals
Are lymphoid follicles present among all secondary lymphoid organs?
Yes, very common
What type of lymphoid follicle involves a loose network of follicular dendritic cells rich in naive and memory B cells?
Primary
Which type of lymphoid follicle occurs after antigen stimulation and includes a germinal center specific for replication and differentiation?
Secondary
What is the difference between the antigen presenting dendritic cells and the follicular dendritic cells?
Follicular dendritic cells are stationary and remain in the lymph node unlike the traveling antigen presenting dendritic cells
Do the B cells of a primary lymphoid follicle “island” likely have different BCRs or are they likely to all be the same?
They are most likely all different which makes the proliferation aspect critical to increase amount of B cells with the same BCRs
What is the normal function of follicular dendritic cells?
Catch and display opsonized antigen to B cells with high affinity receptors
Follicular dendritic cells may be related to what other kind of cell?
Fibroblasts
Are follicular dendritic cells a type of white blood cell?
Noooo
What conditions can result in ectopic follicular dendritic cells?
Autoimmune and inflammatory conditions
Are follicular dendritic cells a part of the parenchymal or stromal cells of the secondary lymphoid organ?
Stromal
Follicular dendritic cells have receptors that bind antigens to what region of antibodies?
Fc (constant tail region)
Can follicular dendritic cells bind to complement proteins?
Yes
What is the purpose of the follicular dendritic cells attaching to and holding opsonized antigens?
BCRs cluster and crosslinks more easily enabling more activation
Germinal centers are associated with which type of lymphoid follicle?
Secondary
Are all the B cells in the germinal center identical clones?
Yes
The formation of germinal centers is associated with what appearance of lymph nodes?
Visibly swollen lymph nodes
The many proliferating B cells involved with a germinal center gives off what microscopic appearance?
“Dark zone”
What happens to the lower affinity BCR B cells of the germinal centers?
They die by apoptosis and are eaten by macrophages
Where does class switching of antibodies occur?
In the “dark zone” of the germinal centers
In those with T cell deficiency, what is the only antibody class that can be created by B cells?
IgM
Peyer’s patches and the appendix are associated with what kind of lymphoid tissue?
GALT (gut-associated lymphoid tissue)
The tonsils and adenoids are associated with what type of lymphoid tissue?
NALT (nasal-associated lymphoid tissue)
Which type of lymphoid tissue is associated with the respiratory system?
BALT (bronchial-associated lymphoid tissue)
All lymphoid tissue types (GALT, BALT, NALT) possess what?
Lymphoid follicles
How can an antigen enter the lymph node?
Via blood or lymph
How does blood enter the lymph node?
Via arterioles
Lymphocytes leave the blood and enter the lymph node via what structures?
High endothelial venules (HEV)
T cells are more common in what area of the lymph node?
Paracortex
Macrophages are found in what specific area of the lymph node?
Subcapsular/marginal sinus
What is the B cell area of the lymph node?
Cortex
What surrounds the lymph node?
Capsule
Where does the lymph first enter the lymph node?
Subcapsular/marginal sinus (that is lined with macrophages)
Where are the primary and secondary lymphoid follicles (filled with B cells) located in the lymph node?
Cortex
What is the area located beneath the cortex and paracortex of the lymph node?
Medulla (medullary sinus)
What are the afferent lymph vessels?
Incoming lymph vessels to the node
What are efferent lymph vessels?
Outgoing lymph vessel to the node
How do lymphocytes enter the lymph node specifically?
Via arteriole or incoming lymph
What is the entry point for B and T cells to enter secondary lymphoid organs from the blood?
High endothelial venules (HEV)
What is the structure of HEV compared to actual endothelial cells?
HEV are columnar in shape and have gaps in between to offer more room for the passage of cells compared to actual endothelial tissue
At rest, what percentage of cardiac output goes through the spleen?
5%
How long does it take to screen all the blood in your body?
30 minutes
What kind of lymph vessels are not seen bringing lymph to the spleen?
No afferent lymphatics
What drains the thoracic duct?
Cisterna chyli
What type of cells dominate in the marginal sinuses?
Macrophages
Blood entering the spleen must filter back out to what vein?
Splenic vein
What area of the spleen consists of B cells?
Area between the periarteriolar lymphocyte sheath (PALS) and marginal sinus
In what location of the spleen are T cells dominant?
Periarteriolar lymphocyte sheath (PALS)
Does red or white pulp make up the bulk of the spleen?
Red
Where is the site of red blood cell destruction of the spleen?
Red pulp
What occurs during RBC destruction?
Hemoglobin: globin is broken down into individual amino acids and heme is broken down into bilirubin
What effect does vagal stimulation have on the macrophage response in the spleen?
Inhibition (cholinergic anti inflammatory reflex)
Where is the white pulp of the spleen located?
Within the red pulp
Where is the periarteriolar lymphocyte sheath?
Surrounding the center arteriole
What surrounds both the PALS and the follicle?
Perifollicular zone
The PALS is made up of primarily what kind of cells?
T cells
Follicles are made primarily of what kind of cells?
B cells (full of germinal centers, B cell corona, and marginal zone)
Adults have about how many Peyer’s patches?
200
What is the function of M cells (microfold cells)?
Enclose intestinal antigens in vesicles called endosomes
Do M cells posses microvilli or mucus?
No
After an antigen is packaged in an endosome by an M cell in the intestines, where can it be taken?
To the Peyer’s patches
What do Peyer’s patches specialize in?
Making helper T cells that tell B cells to make IgA and making helper T cells make a Th2 cytokine profile
Th2 bias is preferable in what location of the body?
Gut
What interleukins are associated with the Th2 cytokine bias?
IL-4, IL-5, and IL-13
What governs the traveling of T cells?
Adhesion molecules
Do adhesion molecules allow more freedom for travel for naive or experienced T cells?
Naive
Why would it be detrimental to enable experienced T cells to have more travel room?
Possibility for self damage (autoimmune)
When T cells previously used in the gut are reactivated, where are they likely to go?
Back to the gut (where they were originally activated) due to their restricted travel by adhesion molecules
Where do experienced B cells tend to settle down?
In bone marrow and spleen to make antibodies
Where can can specialized populations of lymphocytes be found besides lymphoid tissue?
Liver, lamina propria of the gut, base of the epithelial lining of the gut, reproductive epithelia
What seems to be the important role of lymphocyte populations outside of the lymphoid tissue?
Protection from infection
