Lymphoid Organs Flashcards
innate immunity specialized cell examples?
granulocytes, macrophages, dendritic cells, natural killer cels
examples of soluble factors of the innate immunity?
complement, c-reactive protein, mannose binding lectin, defensins
what does the innate immune system respond to?
cues from adaptive system
specialized cells of the adaptive immunity?
lymphocytes
both the innate and adaptive immune system are derived from the ________
hematopoietic stem cell
the lymphoid stem cell produces what?
pre-T-cells
pre-B-cells
pre-T-cells and pre-B-cells mature into the _______
naive B and T cells
what type of lymphocytes are in circulation?
naive B and T Cells- activated when they encounter anitigen
the thymus is formed from what branchial/ pharyngeal structure?
3rd pharyngeal pouch
involution?
the thymus shrinks as you age
problems associated with thymus removal?
young = bad
no problems older in life
what divides the thymus into lobes and lobules?
septa
the thymus is what type of organ?
Function?
lympho-epithelial organ: Supports the development of T-cells.
what is central tolerance?
how?
prevents autoimmunity
-negative selection in the medulla test to see if the pre-T-cell binds to the self antigen with too high of affinity
what type of lymphocytes are encountered in the peripheral lymphatic tissue?
activated B and T cells
color of the cortex and medulla of the thymus?
cortex= dark medulla = lighter
what are thymic epithelial reticilar cells?
antigen presenting cells
thymocytes in the thymic cortex?
t-lymphoblasts
what are hassall corpuscles?
where are they found?
- secrete cytokines the control local dendritic cells
- unique to the thymic medulla
what forms hassall corpuscles?
where are they found?
- large aggregates of thymic epithelial cells form this
- thymic medulla
what promotoes the development of regulator -T cells for peripheral tollerance?
thymic medulla
where are high endothelial venules located?
thymic medulla
what are high endothelial venules
specialized post capillary venules that serve as entry and exit points for lymphocytes
what type of epithelium are high endothelial venules?
cuboidal
where does positive selection occur?
the cortex
where does negative selection occur?
the medulla
MHC-1 interacts with what in positive selection?
MHC-1 interacts with CD8 (cytotoxic T cells)
MHC-2 interacts with what in positive selection?
MHC-2 interacts with CD4 (helper T-cells)
what type of molecule are self antigens?
MHC
Does a pre-T=cells naive T-cell receptor have a moderate affinity (properly bind) to host MHC expressed on reticular cells?
no = apoptosis yes= cell receives cytokines to become a single positive cell (CD4 or CD8)
survivors of positive selection go where next?
negative selection in the medulla
what causes death of pre-T-cells in negative selection
if pre-t-cell’s naive t-cell receptor binds with too high affinity to MHC
to survive negative selection , a t-cell must do what?
t-cells must not recognize self antigens in negative selection
-failure to recognized self antigen = survival
what is peripheral tolerance
generation of hyporesponsiveness in lymphatics(periphery) which encounters antigen in the absence of the costimulatory signals that accompany inflammation.
what aids in peripheral tolerance?
t-reg cells : suppress activation of effector cells with self reactive receptors
example of thymus dependent area?
lymph nodes/ spleen, paracortex of lymph nodes, germinal centers
-areas staffed by t-cells affected if thymus is missing
3 regions of the lymph node?
- cortex
- paracortex
- medulla
what separates the lymph node?
trabecula - carries blood vessels like septa
afferent lymphatic vessels enter the lymph node where>
outer surface of cortex to the subcapsular sinus
wet lymph node organs and immunoglobulin responsible
gut, lungs oral,
IgA
dry lymph node organs and immunoglobulin responsible
axilla, groin
IgG
what is the hilum?
efferent lymphatic vessels exits, vein, artery and nerve eneter and exit here
the subcapsular sinus has what type of epithelium?
discontinuous - fenestrated
what forms lymphoid nodules?
formed by t-helper cells and proliferating B-lymphoblasts
what cell supports most of the lymphoid organs?
reticular cells
what type of cells are found in the paracortex?
only T- Cells!!!!!!!!!
-lacks B-cell lymphoid nodules
90% of lymphocytes enter the lymph nodes via ________ located in the _________
high endothelial venules
paracortex
medullary cords
branched cord like masses of lymphocytes= plasma cells
medullary sinus
dilated space with discontinuous epithelium that separates cords
what is the first antibody secreted?
IgM
wound in finger, what are the 6 steps?
- dendritic cells activate and leave tissue carrying antigen
- transport in lymph vessel to afferent lymph vessels
- helper T-cells activated by antigen
- cytokines
- b-cell binds to helper t-cell
- plasma cells secrete antibodies
where does isotype switching occur?
germinal centers
what is required for isotype switching?
- requires thymus interaction with B-cells
- b-cell needs to be activated by T-helper cell
what forms cords in the medulla?
plasma cells
IgG
- most abundant
- soluble
- can cross placenta to fetus = passive immunity
- most important for long-term resistance
IgE
- mast cells, basophile
- parasitic and allergic reactions - release histamine
IgA
- saliva, sweat, intestinal juice, milk
- helps precent attachment of pathogens to epithelial surfaces
IgD
attached to external surface of B-cell = antigen receptor
lymphoma is there pain?
no pain associated w a lymphoma b/c tumors do not release cytokines. normal lymph node swelling is painful bc cytokines are released from the inflammatory process
function of the spleen?
filter blood by trapping antigens and pathogens.
turns over old RBC’s
3 areas of the spleen
- red pulp - lighter colored
- white pulp - darker red (more RBC’s)
- marginal zone - boundary between red and white pulp
contents of red pulp
large sinusoids and connective tissue aggregates called cords
function of the red pulp?
blood cell turnover and antigen trapping
contents of white pulp?
function?
aggregates of lymphocytes surrounding central arteries
-mostly B-cells around germinal centers
involved in immune response
what is the flow of blood through the spleen?
trabecular artery- central artery - penicillary artery
what surrounds central arteries?
periarterial lymphatic sheath (T-cell sheath)= primary T-cells= white pulp
culling
what does it?
where?
- macrophages engulf old RBC’s and destroy them
- occurs when moving through splenic cord and red pulp to the sinusoid
pitting
macrophages engulf nuclear fragments or parasites leaving the rest of the cell
what causes the central artery to be eccentric?
clonal expansion from B-cell response
what makes up the majority of all immune cells?
mucosal associated lymphatic tissue
-ex tonsils, peyer patches, apendix
what composes the MALT
mostly b-cells, some t-helper cells
gender differences in women in regards to immunoglobulins and autoimmune diseases
women have a more robust immune system with more IgG
-but they have more autoimmune diseases
open circulation of the spleen
penicullar arterioles leave white pulp and dump blood directly into red pulp. Blood cells push through Ct and return to circulation by sinusoidal capillaries
what are two examples of antigen presenting cells?
macrophages and dendritic cells
what induces lymphoid progenitor to become pre-T-cells.
epithelial reticular cells
Function of t-reg cells
suppress activation of effector cells with self reactive receptors
-aids in peripheral tollerence
_________ on the lymphocyte helps recognize glycoproteins on endothelial cells?
L-selectin
what is L-selectin?
present on on the lymphocytes. it helps recognize glycoproteins on endothelial cells
what forms the blood thymus barrier?
thymic epithelial cells
