Organs and Tissues of the Immune System Flashcards
What are the primary lymphoid organs of the B and T cells?
B cells mature in bone marrow
T cells mature in thymus (precursor cells migrate from bone marrow)
Once in the thymus, T cells begin expressing surface ____ molecules
TCR
These are the organs where lymphocytes respond to antigens by undergoing clonal selection and proliferation
secondary lymphoid organs
The most important secondary lymphoid organs are?
spleen, lymph nodes, MALT
What is the major site of hematopoiesis in adults?
bone marrow - especially sternum, vertebrae, iliac bones, and ribs
Hematopoietic stem cells express what two markers?
CD34 and Stem cell antigen-1
Stem cell differentiation is stimulated by cytokines secreted by bone marrow ___ cells
stromal
Give the stages of B cell maturation in the bone marrow
Stem cell - pro B cell - pre B cell - Immature B cell - Mature B cell - memory or plasma cell
The thymus is an encapsulated organ that develops from the epithelium of the ___ pharyngeal pouch. It is a bilobed structure that reaches its maximum size at ____ and then atrophies at age
third; puberty
Persons with a chromosome __ deletion are born with little or no thymus and suffer from ____ syndrome. These patients are highly susceptible to viral infections and cancer because they have few or no functional T cells
22; DiGeorge
The subscapular region of the thymus contains what?
double-negative thymocytes that expresses neither CD4 or CD8 and no TCR
At some point in the subscapular region, double-negative cells being partial expression of the TCR. At this point, they are called what?
pre T cells
The cortex region of the thymus contains what?
immature thymocytes and double-positive T cell precursors
The medulla of the thymus contains what?
mature single-positive T cells
note: medulla also contains Hassal’s corpuscles which may play a role in DC or T reg cell differentiation
Lymph nodes respond primarily to what?
antigens entering the body through the skin and subcutaneous tissues
What are the 3 functions of lymph nodes?
survey of the lymph by macrophages, storage and activation of B and T cells, antibody production
The lymph system’s primary function is what?
isolate infectious agents and cellular debris from the rest of the body
Lymph filters through ___ where sentry ___ lie waiting to engulf and destroy any foreign particles in the fluid
nodes; macrophages
Antigens processed by the macrophages in lymph nodes are presented to ___ cells, which secrete cytokines in response
T helper
note: activate B cells to make antibodies and Tc cells to kill infected host cells
Efferent lymphatics from most of the body eventually converge in the ___ duct, which empties into the left subclavian vein and then into the superior vena cava
thoracic
note: in this way, lymphocytes re-enter the circulation
Re-ciruclation of the lymphocytes increases the likelihood of what?
that a given lymphocyte will make contact with the pathogen for which it is specific
The Cortex (B cell area) of the lymph node has primary and secondary follicles. What do each contain?
primary follicle: naive B cells that have never contacted antigen
secondary follicle: germinal centers composed of B cells undergoing mitosis in response to antigen stimulation
The paracortex (T cell area) of the lymph node contains what?
T cells
Lymphocytes in the blood enter the paracortex region of the lymph node through specialized post-capillary venues called ___ ____ ___
high endothelial venules (HEVs)
