The appendix is a significant part of the mucousa associated ymphoid tissue with its ________ and __________ filled with lymphocytes and lymphoid follicles.
Lamina propria; submucosa
What is the role of the epithelial reticular cells of the thymus?
Form the structural component of the parenchyma, which lacks collagen
What are the major components of the parenchyma of the spleen?
White Pulp
Red Pulp
What is the role of thymic nurse cells?
They can engulf as many as 20 lymphocytes. A portion of those lymphocytes are released, which the other portion undergo apoptosis
HEVs are found in the _____________ of lymph nodes
paracortex
The palatine tonsil is invaginated by deep grooves called ___________
Tonsillar Crypts
Is the thymus encapsulated or not capsulated? What can be found between the two lobes of the thymus? What can those lobes further be compartmentalized into?
Encapsulated; Septa; Cortex and Medulla
What are the two main tissue architecture types of lymphoid sytem?
Diffuse
Follucular
Lymphocytes originate in __________
Bone Marrow
Foreign proteins that have been phagocytized are transferred to vesicles containing ________ protein of antigen-presenting cells. This attracts the attention of ____________ cells that stimulate the production of _______ against the bacterium.
MHC II; Helper T; antibodies
Central arteries are surrounded by _____________ of T- cells.
Peri-Arteriolar Lymphoid Sheath
Two types of specific resistance
Cell-mediated immunity
Antibody- mediated immunity
What are the roles of the secondary lymphatic organs? What are the secondary lymphatic organs/tissues?
Site where most immune responses occur
Lymph nodes, spleen, and lymphatic nodules
Which of the Major Histocompatibility Complexes is found in all nucleated cells?
MHC I
Thymus undergoes _____ with less activity in the adult. Atrophy of the ____, which is partially replaced by _________
Involution; parenchyma; adipose tissue
The pharyngeal tonsil covered by ____________ epithelium
pseudostratified columnar
What is the difference between epithelium in palatine tonsil vs epithelium in lingual tonsil?
The lingual tonsil epithelium is surrounded by skeletal muscle
A specialized subtype of reticular epithelial cells
Thymic nurse cells
How can the cortex be distinguished from the medulla of the thymus?
The cortex is darkly stained with densely packed lymphocytes. The medulla is lighter stained with fewer lymphocytes but more epithelial reticular cells.
Antigen- presenting cells display antigens alongside _________
Major Histocompatibility Proteins (MHC)
Helper T cells stimulate ______ cells
B
What are the major roles of the lymphatic system?
Draining excess intersitial fluid and plasma proteins from the tissue spance
Transporting dietary lipids and vitamins from GI tract to the blood
Facilitating immune response
Steps to stimulation of Cytotoxic T Cells
- CD8 binds to the MHC I molecule of various cells. Cell receptor on the cytotoxic cell binds with the abnormal antigen of the various cells.
- Interleukin 2 that is released from the Helper T Cell activated the cytotoxic T cell
- Activated cytotoxic T cell proliferates and differentiates into activated and memory cytotoxic t cells
_________ of cortical capillaries prevent entry of blood-borne molecules into the cortex of the thymus. This prevents exposure of developing_________ to _________, which could cause their apoptosis.
Tight junctions; T cells; Plasma antigens
What type of cells make up the stroma? Is the stroma visible and clear?
Epithelial cells; No they are oscured by the lymphocytes
What tissue makes up the capsule of Palatine Tonsils?
Dense irregular connective tissue
What are the components of the Splenic sinuses?
Full of blood because the spleen acts as a filter of blood. They are lined by endothelium
Where are the B cells located in the Spleen?
In the germinal center of follicles found in the white pulp
What are the functions of epithelial reticular cells?
Attract lymphocytes to the thymus and guide their development
What is the stroma?
Supporting cellular framework of connective tissue which contains blood vessels and nerves and gives structure to the thymus
Cytotoxic T cells have which protein?
CD8
What are the components of the Cords of Billroth?
WBCs, macrophages, RBCs, B and T lymphocytes
What are the cells of the thymus?
Pre T cells
T lymphocytes
Epithelial reticular cells
Thymic nurse cells
Dendritic cells
Where do thymic dendritic cells originate? What is their function?
They originate in bone marrow.
They stimulate development of regulatory T cells that suppress reactions to self-proteins
What can be found beneath the epithelium of palatine tonsils?
Lymphatic nodules in connective tissue
_________surrounds the white pulp and is divided to __________ and ___________.
Red Pulp; splenic cords; spenic sinuses
The lingual tonsil is covered by ____________epithelium
Stratified squamous
Which organs are apart of the lymphatic system?
Red Bone marror
Thymus
Spleen
Lymph nodes
Tonsils
What is nonspecific resistance to disease?
General defensive mechanisms effective on a wide range of pathogens
The thymus is a _____ lymphoid orgain in that it supplies other lymphoid organs and tissues with __________
Primary; T- Lymphocytes
Examples of a Mucousa associated lymphoid tissue
Appendix
How are millions of different types of lymphocytes generated?
In the parenchyma, T-cell receptor genes are rearranged so that mature T cells obtain specific surface markers
All T lymphocytes have cell surface protein receptors (TCRs) with variable regions that recognize specific antigens. Cell activation requires costimulation by the ____________ and either ________ or _________, which characterize helper and cytotoxic T cells, respectively
TCR; CD4; CD8
How do RBCs leave the spleen?
They must push past macrophages to enter sinusoids and leave the spleen
__________ play an important role in isolating T cells from __________ during their development.
Stroma; foreign antigens
Why do lymphocytes adhere to HEVs?
HEVs possess addressin proteins that bind to selectin proteins of lymphocytes.
What makes up the capsule of lympoid tissue?
Connective tissue
Is the spleen and encapsulated organ?
Yes
Steps to stimulation of Helper T Cells
- CD4 binds to MHCII molecule of the antigen presenting cell. The helper T cell receptor interacts with antigen on the antigen presenting cell
- Helper T Cells secrete Interleukin 2 which stimulates the helper T lymphocytes
- Activated T Lymphocytes proliferate and differentiate to produce new activated and memory T Lymphocytes
In the medulla, epithelial reticular cells also form ___________
Hassall’s Corpuscles
The capsule of the spleen extends to form ________ which contain the ___________ and _________-
Trabeculae; trabecular arteries; trabecular veins
Are the tonsils capsulated?
Partly
Components of Red Pulp
Cord of Billroth
Sinuses
Stroma
What is the mechanism for lymphocyte migration to the tonsils?
The specialized cubodial endothelium cells of HEVs possess proteins that slow down lymphocytes and encourage them to exit the HEV and enter the tonsil
What are the two distinct areas of lymphoid follicles? How can they be distinguished?
Mantle- darker stained, smaller, resting lymphocytes
Germinal center- Lighter stained, larger, activated B cells
What is the role of epithelial reticular cells in the Hassall’s corpuscles? What affect does this have?
Epithelial reticular cells of the Hassall’s corpuscles secrete Thymic Stromal Lymphopoietin( TSL).
TSL stimulate dendritic cells to hasten the maturation of regulatory T cells that suppress the auto-immune reactions against “self” proteins.
What is the MHC pathway for endogenous antigens digested in proteosomes?
- MHC I and antigen formed in rER
- Travel to Golgi
- Travel to vesicle
- Mets with the Cytotoxic T- Cell (CD8)
_____% of T cells formed in the thymus are destroyed to prevent reactions againts “self” proteins.
95
What happens in the “nude miuse” case?
The mouse has defects in karatin- containing hair follicles and in keratin-containg thymic epithelial reticular cells. The mice cannot grow hair, and can not populate a thymus with lymphocytes, and so cannot reject the skin grafts from other mice.
Pre T cells enter the _______ and are “educated” by ________ cells. The T cells are then released from the cortex for final stimulation by __________ in the medulla.
Cortex; Reticular epithelial; dedritic cells
Macrophages present antigens to ___________-
Lymphocytes
What are the three types of T Cells
Cytotoxic
Helper
Regulatory T Cells
What is the vascular pattern of the spleen?
- Trabecular artery
- Central arteriole
- Penicillar arterioles
- Sheathed capillaries
- Trabecular vein
What are the two types of lymphoid tissue? Which organs fall under each type?
Encapsulated (Spleen, Thymus, Lymph Nodes)
Unencapsulated (Tonsils, Peyer’s Patches, Lymphoid nodules in GI tract, respiratory tract, urinary and reproductive tracts)
Which lymph organ lacks lymph follicles?
Thymus because it has no B cells
Do all lymphoid follicles have geminal centers?
No
The surface of the palatine tonsil is covered by ___________ epithelium.
Stratified squamous nonkeratinized epithelium
Where are dendritic cells located?
Medulla
A subtype of epithelial reticular cells expresses a huge variety of proteins under the command of a transcription facter called ___________. How many proteins are expressed? What happens if a T cell binds to these proteins?
AIRE (Autoimmune Regulatory protein)
3000
It is killed via apoptosis
What is the parenchyma?
The epithelial, secreting cells of the thymus which perform the thymus’s essential function
_________________ is a cytokine that induces differentiation of naive helper T cells (Th0 cells) to Th2 cells.
The interleukin 4 (IL4, IL-4)
_________ cells migrate to the thymus for further development.
Pre-T
What are the two tissue components of the thymus?
The parenchyma and stroma
What is lymphoid tissue?
Connective tissue with a rich supply of lymphocytes
What are the roles of the primary lymphatic organs? What are the primary lymphatic organs
Provide environment for stem cells to divide and mature into B and T lymphocytes
Red bone marrow- Gives rise to mature B cells
Thymus- Give rise to T cells
How do cytotoxic T cells kill cells?
Secrete protein subunits called perforins, which can form holes in cell membranes
Secrete destructive enzymes called granzymes
Produce pro-apoptotic protein, FAS ligand
Mutations in an epithelial transcription factor called __ damages both epithelial cells and the thymus of the “nude mouse”
Foxn
Helper T Cell have which type of protein?
CD4
How does the lymphatic system facilitate immune responses?
Recognize microbes or abnormal cells and responding by killing them directly or secreting antibodies that cause their destruction
Stimulation B lymphocytes (Pathway)
- Free antigen binds to the B cell receptor. The B cell engulfes, processes, and presents antigen to the Helper T Cells
- Interleukin 2 is released from Helper T Cells and stimulate B cells
- Activated B Cells proliferate and differentiate into activated and memory cells