Lecture 6 - Lymph Flashcards
3 lines of defense
physical barrier, innate (non-specific) immunity, acquired (specific) immunity
Commensals
bacteria with a symbiotic relationship in the respiratory and GI tract
Cells that participate in innate immunity
Mastocytes, granulocytes, and agranulocytes (macrophages and Natural T killer lymphocyte)
Acquired immunity
bacteria will be degraded by lysosome. binding of the MHC and will present an IgD and bind to the B lymphocyte to activate it, causing proliferation of T cells and B cells
Function of lymph system
antigen recognition and antigen inactivation/elimination
Cellular immunity
T lymphocyte activated by contact with a MHC-1. Will produce memory and cytotoxic lymphocytes (perforin lyses the cell).
Central lymphoid tissues
Thymus and bone marrow (bursal)
Where do T cells undergo maturation?
Thymus
Where do B cells undergo maturation?
Bone marrow
B cells are produced where in the fetus?
Liver in the second trimester.
Plasma cells unique features
high RER for immunoglobulin production and eccentric nucleus with a cartwheel arrangement of heterochromatin
Immunoglobulin structure
heavy and light chains. 2 disulfide bonds between heavy and 1 between heavy to light. Variable portion allows for specificity (somatic recombination)
Somatic recombination
Light chain has different sequences that get shuffled, producing a random variation of exons. Occurs in T cell receptor and B cells.
IgG
most common. Monomere. activates phagocytosis, neutralizes antigens, protects newborn. In blood, lymph intestinal lumen
IgM
pentamere. First antibodies to be produced in an initial immune response. Found on B lymphocytes surface
IgA
Dimer with secretory component. Protects the surface of mucosas for it resists proteolysis. Produced in B lymphocytes of the lamina propria and presentes as dimers in secretions.
IgD
Monomere. Functions as a receptor to antigens triggering B cell activation. Presents only on surface of B lymphocytes
IgE
Monomer. participates in allergy and lyses parasitic worms. Bound to the surface mastocytes and basophiles
Immunization
antigen to promote a primary response and a second antigen exposure produces a quicker and stronger secondary response.
Primary response
more IgM than IgG
Secondary response
more IgG than IgM
Aggulination
antibodies bind to antigen
Opsonization
binding of antibodies stimulate phagocytosis
Neutralization
binding of antibody to microorganisms blockes their adhesion to cells and inactivates toxins
cytotoxicity
antibodies adhering to the surface of worms activating cells of immune system and inducing them to liberate chemical agents that attack the surface
complement activation
binding of antibodies triggers the complement cascade to produce membrane attack complex and causes cell lysis.
Helper T cells
CD4. promote the activation, proliferation, and differentiation of B lymphocytes.
Cytotoxic T Cells
CD8. MHC- I complement to TC receptor, will release either perforin (lyses cell) or fas ligand (apoptosis)
PD-1 receptor (suppressor T cells)
expressed on T cells. down regulate the immune system by preventing activation of T cells. Inhibitors of PD-1 thus activate immune system.
Chemotherapy
cuases microtubules to dissolve, destroying centrioles in highly mitotic cancer cells
Immunotherapy
change the way the immune response treats the cancer
Memory cells
produced from both T cells and B cells
MHC I
present on all cell types. CD8 (cytotoxic) T cells. dont pass through endosome-lysosome vesicles.
MHC II
present of APCs (differentiated from monocytes). CD4 cells (helper). Pass through endosome-lysosome vesicles. Will cause release of cytokines to promote B cell differentiation.
Perforin
released by CD8 and cause cell lyse
Fas ligand
released by CD8. Cause cell apoptosis (cell suicide).
Necrosis
murder of a cell
HIV
attacks the helper T cells.
Encapsulated peripheral lymphoid organs
lymph nodes and spleen
Unecapsulated peripheral lymphoid organs
MALT (mucosa-associated lymphatic tissue) found in submucosal membranes of the body. About 85% of all lymph tissue
B cells located where in lymph node
Cortical nodules in the medulla
T cells located where in lymph nodes
paracortex
B cells located where in spleen
lymphoid nodules
T cells located where in spleen
PALS (periarterial lymphatic sheaths)
More prominent cell type found in blood
T cells (major part of the circulating lymph tissue)
More prominent cell type found in lymph
T cells
More prominent cell type found in mucosal tissues
B cell (such as GI tract)
B cells primarily produce what antigen
IgA
How is IgA protected
a secretory piece/component is added by epithelial cells and protects it against lysosomal degradation and then clipped at the apical surface.
Solitary nodules
GI and respiratory. Unencapsulated. primary and secondary nodules
Primary nodule
naive B cells.
secondary nodule
cap or mantle with naive B cells (stains darker); Germinal center (stains lighter) with activation of immune cells (B, helper T, dendritic cells, and tingible bodies)
Tonsil
discontinuous ring of lymphatic tissue. Apical surface - stratified squam non-keratinized. Can have primary and secondary nodules
Aggregated nodules
Tonsils, peyers patches, vermiform appendix
Peyer’s Patches
small intestine - ilium of the GI tract. Can form and dissipate. Can produce primary nodules
Microfold cells
transport antigen to macrophages for stimulation of B and T cells.
Appendix
terminal narrowed tip of the cecum. Lymph tissue will age.
Thymus
encapsulated and can branch to produce trabeculae producing lobules (cortex and medulla).
What forms the microframework of the thymus?
epithelial reticular cells
Cortex of the thymus
where T cells are maturing.
Hassal’s corpuscle
collection of dead epithelial reticular cells found in the medulla of the thymus.
Thymus efficiency
95% of developing thymocytes are destroyed. Where T cells will not recognize and thus avoid macrophages.
Blood - thymus barrier
prevents blood borne elements from having early access to the thymus cells during their recombination.
Immunosenescence
as you age, a decrease in available T cells and fat replaces.. Increases change of inability to fit off an infection.
Where does the lymphatic system brain back into?
the venous cava.
Lymph node function
filter lymph fluid and hold T and B cells
Direction of lymph fluid in lymph node
afferent lymphatics into the subcapsular sinus, then the travecular sinus, to the medullary sinus and exit the efferent lymphatic (hilum).
Scaffold of lymph node
reticular cells and fibers (argenophylic)
Direction of blood in lymph node
in through Hilum, goes to paracrotical region and does a u turn to exit out of hilum.
Lymph node cortex components
superficial cortex - B cells and APC
paracortex - T cells and APC
Lymph node medulla component
Plasma cells
Type of endothelium cells seen in the postcapillary high endothelial venule
Cuboidal endothelium. Allow for lymphocytes to squeeze into the parenchyma of the node
Spleen function
filters blood. platelet storage. immune response to blood born antigens. hematopoiesis if necessary.
Red pulp of spleen
erythrocytes (no nuclei) and stain pink.
White pulp of spleen
abundance of leukocytes (nuclei) and stain a purpleish color
Blood circulation of spleen
exits white pulp into red pulp which contain sinusoids looking for aged or damaged erythrocytes.
Open sinusoid
open circulation allows for a slow filtration
Closed sinusoid
close circulation does not allow erythrocytes to leave, thus a fast filtration
Where are postcapillary high endothelial venule found?
only in lymph nodes (paracortex)
Stain used for iron stain in spleen
prussian blue
