Hematopoiesis III: Immune System and Lymphoid Organs Flashcards
what are the two general functions of the lymphoid systems?
- fluid balance
2. destroying foreign microorganisms and infected cells
what are the two broad divisions of the immune system?
innate and adaptive
name the general classes of molecules that can activate the innate immune response
- PAMP (pathogen-associated molecular pattern)
2. DAMP (danger or damage-associated molecular pattern)
what are the 4 main cell types that are involved in the innate immune response
- macrophages
- neutrophils
- eosinophils
- NK cells
PAMP
pathogen-associated molecular pattern: may clear an infection before the adaptive response is activated
DAMP
danger or damage-associated molecular pattern: induced inflammation when there is tissue damage (e.g. bruise)
PRR
pattern recognition receptor: term that includes things like PAMP and DAMP. basically something that causes the innate immune system to respond
what can occur if the innate immune system is hyperactive?
autoinflammatory disease
which is faster to respond, innate or adaptive immunity?
innate
epitope
AKA: antigenic determinant. specific portion of antigen that is recognized and stimulates an immune response
why do vaccines increase the speed and vigor of the immune system’s response to a specific antigen?
memory cells that are created in response to vaccination allow for a fast and vigorous immune response following introduction of their specific antigen
what are the two main branches of the adaptive immune system?
humoral and cellular
immunocompetent cell
lymphoid cell that is capable of reacting to an Ag, or able to become active in cell0mediate immunity or delayed hypersensitivity rxns
immune response
a defense function of the body that protects against invading pathogens, foreign tissues, and malignancies (consists of humoral and cell-mediated immune response)
humoral immunity
B lymphocytes produce Abs that react w/ specific antigens. Ag-Ab rxns that activate compliment cascade
cellular immunity
T lymphocytes mobilize tissue macrophages in the presence of foreign antigens
memory cells
T and B lymphocytes that mediate immunological memory. help mediate subsequent Ag invasions
APC
antigen presenting cells, present specific Ag to T cells along w/ surface proteins that act as co-stimulatory molecules
what type of cell is the most common APC to activate naive T cells?
dendritic cells
list the central lymphoid organs
thymus and bone marrow
what is the function of the central lymphoid tissues
the site of lymphocyte differentiation
list the peripheral lymphoid organs
lymph nodes, spleen, GALT (gut associated lymphoid tissue- e.g. tonsils and Peyer’s patches)
GALT
gut-associated lymphoid tissue- tonsils and Peyer’s patches
what is the function of the peripheral lymphoid tissues
where immune cells come into contact with Ags or infected cells
Waldeyer’s ring
an example of partially encapsulated confluent lymphoid follicles. palatine, pharyngeal, and lingual tonsils (encircle the pharynx- gateway to the gut)
Peyer’s patches
an example of non-encapsulated confluent lymphoid follicles. found in the ilium
appendix
an example of non-encapsulated confluent lymphoid follicles. found inferior to the ascending large intestine (RLQ)
immunoglobulin
(Ig/antibody) a molecule that recognizes and binds a pathogen or infected cell to initate an immune response
what are the 3 main effects that an antibody can have?
- block activity of Ag
- mark Ag for phagocytosis
- activate complement cystem
antigen
molecule that binds to an Ab, something that can cause an immune response.
innate (natural) immunity
primitive immunity that is present w/o prior Ag stimulation, recognizes PAMPS and DAMPS
what determines pathogen specificity of the innate immune system?
germline DNA (as opposed to prior activation by encounter w/ an Ag)
adaptive immunity
more specific, learned immune response that is dependent on lymphocytic recognition of Ags (Ags can be soluble or fixed to whole cells- e.g. LPS on bacteria)
immunodeficiency
suceptibility to infection, cancer, and other diseases because of an inadequate immune response
what is the process of development and maturation for T cells?
- produced in the bone marrow
- released into blood stream
- mature in the thymus
- activated in thymus to become either memory T cells, T helpers, T cytotoxic
what is the process of development and maturation for B cells?
- produced and mature in bone marrow
- released into blood stream
- find peripheral lymphoid tissue where they remain (inactivated)
- once they are activated by Ag, they proliferate and terminally differentiate into plasma cells or memory cells
diffuse lymphoid tissue
tissue w/ scattered B and T lymphocytes, common in mucosal linings, associated w/ GI, respiratory, and urinary systems
lymphoid follicles (nodules)
structures organized for the activation of B cells (may be solitary or grouped), helper T cells around periphery, can be primary or secondary (secondary have germinal centers)
discuss the structure of the tonsils
connective tissue capsule w/ epithelium that forms crypts to increase SA. stroma made up of reticular cells and fibers. intraepithelial lymphocytes housed w/i epithelium in nodules.
afferent vessels
lymph vessel that carries fluid into lymph node
efferent vessels
lymph vessel that drains lymph node at hilum
follicular cortex
outer portion of the lymph node, B cell rich area, rich capillary network, lots of follicles
what types structures exit the lymph node at the hilum?
- efferent lymph vessels
- blood vessels
- nerves
parafollicular cortex
lymph node layer that is just deep to the follicular cortex, T cell zone
medulla of the lymph node
inner portion of the lymph node, contains medullary cords and sinuses, rich in macrophages and plasma cells
cortical sinuses
AKA trabecular or intermediate sinuses. sinuses of the cortex that drain fluid into the medullary sinuses
medullary sinuses
collect lymph that has filtered thru. cortex. macrophages, drain to efferent lymph vessels.
what are the 5 main things that can be found in lymph fluid that is entering a node via afferent vessels?
- soluble substances
- dendritic cells (APC kind)
- lymphocytes (B and T cells)
- possibly microbes
- possibly metastasizing cancer cells
medullary cords
cords of lymphatic tissue found in the medulla of the node, made up of plasma cells, B cells, and macrophages
where might you find a reticular fiber stroma w/i the lymph node?
cortex and medullary cords
what types of cells maintain the reticular stroma of the cortex and medullary cords?
fibroblastic reticular cells
where are germinal centers found in the lymph node?
follicular cortex
what is the function of the lymphoid follicles?
activate B cells (can be primary or secondary depending on presence of germinal centers)
what is the structure of the red pulp of the spleen?
venous sinusoids, encircled by reticular fibers and long barrel-like endothelial cells. contain macrophages, plasma cells, blood. blood from from trabecular arteries, to central arteries, to red pulp.
what is the structure of the white pulp of the spleen?
lymphoid tissue made up of PALS (T cells around central artery) and scattered follicles (B cell rich). also contains marginal zone and sinuses that are rich in APCs
what types of cells would you find in PALS of the white pulp of the spleen?
T cells
what types of cells would you find in the follicles of the white pulp of the spleen?
B cells
what types of cells would you find in the marginal zone and sinuses of the white pulp of the spleen?
APCs
briefly, what is the function of the red pulp of the spleen? white pulp?
red pulp: filtration
white pulp: lymphoid tissue
PALS
periarterial lymphatic sheath, T cells surrounding an artery
splenic sinusoids
wide blood vessels w/i the red pulp of the spleen that drain into the splenic trabecular arteries; filter out blood as it enters the spleen
splenic cords
cords w/i the red pulp of the spleen that are rich in macrophages, plasma cells
what are the two main functions of the thymus?
- positive selection of T cells
2. negative selection of T cells
discuss positive selection of T cells in the thymus
first stage of T cell maturation, occurs in cortex of thymus, tested and pass if they have reactivity to “non-self”
discuss negative selection of T cells in the thymus
second stage of T cell maturation, occurs in medulla of thymus, tested and pass if response is “just right” (i.e. not hyper active)
thymocytes
immature T cells that are found in the cortex of the thymus
what types of cells are in the thymus to break down immature T cells that do not pass positive selection process in the cortex?
macrophages
blood thymus barrier
impermeable epithelium lines vessel walls (tight junctions and thickened basement membrane), macrophages in perivascular space. reticular cells have tight junctions to keep antigens out
discuss the cortex of the thymus
houses thymocytes, site of DNA rearrangements that increase diversity of antigen recognition
discuss the medulla of the thymus
houses T cells, Hassal’s corpuscles, supportive epithelial reticular cell stroma
Hassal’s corpuscle
concentric, flattened, epithelial reticular cells w/i medulla of thymus. may calcify, function is uncertain, may secrete ILs needed for thymic function
