lecture 16 Flashcards
immunity
resistance to damage or disease
susceptibility
vulnerability to damage or disease
pathogens
disease causing mircoorganisms like bacteria, fungi, viruses, and parasites
lymphatic system consists of:
lymph and lymph vessels
3 main functions of lymphatic system
drains excess body fluid
defends the body against disease
transport dietary lipids
compared to interstitial fluid and blood, lymph is: (3)
richer in dietary lipids
carried in lymph vessels/organs
filtered through lymphoid tissues
what mechanism allows fluid to enter lymph vessels but not exit?
the endothelial cells overlap, so when fluid is inside, they are pushed shut like valves
anchoring filaments
- elastic fibres
- allows lymphatic capillaries to attach to surrounding tissues
- can pull endothelial lining open to allow more fluid in
lacteals
specialized lymph capillaries at small intestine that absorb dietary lipids
chyle
lipid rich lymph from small intestine (lacteals)
- creamy white
capillaries merge into _____ whihc merge into ______-
vessels, trunks
right lymphatic duct
not in all people
drains into subclavian vein
left thoracic duct
main path for lymph to return to circulation
largest vessel in body
starts at cisterna chyli
drains into subclavian vein
what % of fluid is returned to circulation
15
primary lymphatic organs
organs that are a site of stem cell division and/or immunocompetence development
red bone marrow
thymus
secondary lymphatic organs
organs where immunocompetent cells perform their defensive functions
spleen
lymph nodes
what do lymphatic tissues lack?
external wrapping called a capsule
mucosa associated lymphoid tissue
MALT
- lymphatic tissues found in lamina propria (basement membrane) of mucous membranes
MALT
mucosa associated lymphoid tissue
lamina propria
basement membrane
aggregated lymphoid follicles location
located in the oleum of the small intestine
tonsils names and function
pharyngeal -1
palatine -2
lingual -2
filter fluid, protect from invasion
red bone marrow
primary lymphatic organ
- contains multipotent stem cells taht give rise to cells of blood
- B and T lymphocytes form here
thymus
primary lymphatic organ
- bilobed gland that shrinks with age
- where T lymphocytes become immunocompetent
thymus lobe parts
outer cortex
- contains epi cells that train T cells
inner medulla
- contains mature T cells and epi cells that die and form thymic corpuscles
spleen
secondary lymphatic organ
- largest mass of lymphatic tissue
- wrapped by visceral peritonial membrane
- has stroma
- has inner parenchyma that contains white and rep pulp
stroma
part of the spleen
- filters fluid
- made of dense CT and reticular fibres + fibroblasts
- provides passage for blood vessels into spleen
inner parenchyma
contains white and red pulp in the spleen
white pulp
contained in the inner parenchyma of the spleen
- contains lymphocytes and macrophages
- surveils blood and defends
- clustered around splenic artery
red pulp
contained in the inner parenchyma of the spleen
- contains RBCs, macrophages, lymphocytes, immune cells
- removes worn out cells
- stores platelets
lymph nodes
bean shaped organs
- capsule made of dense CT, part of organ stroma, forms trabeculae
- has parenchyma that includes both cortexes and medulla
- outer / inner cortex
- innermost medulla
outer cortex of lymph nodes
contains lymph nodules
- clusters of B cells
inner cortex of lymph nodes
- no lymphoid nodules
- site of T cell activity
medulla of lymph nodes
- reticular fibre matrix
- contains activated B cells (plasma cells) + macrophages
lymph flow INTO nodes is:
afferent
lymph flow OUT OF nodes is:
efferent
innate immunity
non specific
- fast defences
- found in all animals
adaptive immunity
specific defences
- must be activated
- only found in vertebrates
subdivisions of innate immunity
external and internal defences
external defences of innate immunity are the:
first line of defence
examples of external defences (6)
epidermis
sebum
sweat
mucous membranes
tears
other body secretions
epidermis as an external defence
keratinized stratifies squamous epi
- physical barier
sebum as an external defence
keeps the skin acidic
sweat as an external defence
keeps skin salty, restricting some organisms from colonizing the skin
mucous membranes as an external defence
covered in mucus that trap invaders
- cilia sweep mucus
tears as an external defence
contain lysozyme, a protein that disrupts bacterial membranes
other secretions of the body as an external defence
urine, vaginal secretions, gastric juices, defecation, vomiting
internal defences of innate immunity are the:
second line of defence
examples of internal defences (5)
antimicrobial substances
natural killer cells
phagocytes
fever
inflammation
antimicrobial substances as an internal defence
(4 substances)
interferons
complement proteins
iron binding proteins
antimicrobial proteins
interferons as an antimicrobial substance and internal defence
proteins made by virally infected body cells that produce antiviral responses in other body cells
complement proteins as an antimicrobial substance and internal defence
proteins that enhance phagocytosis and stimulate lysis of invaders
iron binding proteins as an antimicrobial substance and internal defence
starve microbes of iron found in body tissues (transferrin and ferritin)
antimicrobial proteins as an antimicrobial substance and internal defence
stimulate leukocyte activity, stimulate lysis of invaders
natural killer cells as an internal defence
5-10% of leukocytes in blood/lymph
- attack any cells with foreign antigens
- secrete perforins and granzymes
perforins
proteins that poke holes in cell membranes of attackers, cause cell lysis
secreted by NKCs and CTLs
granzymes
proteins that induce apoptosis
secreted by NKCs and CTLs
phagocytes as an internal defence
cells that engulf other cells or large particles to destroy them
- neutrophils - first responders
- macrophages - differential from monocytes, arrive late
steps of phagocytosis (5)
- chemotaxis
- adherence (binds to invader)
- ingestion (wraps around invader using psuedopods)
- digestion (vesicle fuses lysosome)
- killing (formation of residual bodies)
psuedopods
cytoplasmic extensions during phagocytosis
- forms a special vesicle called a phagosome
phagolysosome
during digestion of phagocytosis
- when a phagosome and lysosome fuse
residual bodies
indigestible molecules from destroyed invaders during phagocytosis
inflammation as an internal defence
immune response to tissue damage
- nonspecific
- 6 steps
6 steps of inflammation
histamine release
rolling
emigration
chemotaxis
tissue disinfection
tissue healing
what is the effect of histamine
calls leukocytes to damage site
- vasodilation
- increases vascular permiability
kinins
proteins that promote vasodilation and increase vascular permiaility
- part of tissue healing
prostaglandins and leukotrienes
eicosanoid lipids that enhance chemotaxis
inflammation signs and symptoms (PRISH)
pain, redness, immobility, swelling, heat
fever as an internal response
unusually high body temps
- product of changes in hypothalamus
how does a fever defend the body from invasion?
creates a non optimal temperature for pathogens
- faster chemical reactions
- faster rate of tissue repair
primary defences from adaptive immunity
lymphocytes
how to lymphocytes defend the body?
each B and T cell expresses antigen receptors
- these allow lymphocytes to recognize unique shapes of antigens
subdivisions of T cells
helper T lymphocytes
cytotoxic T lymphocytes
antigens
any molecule that evokes an immune response
helper T lymphocytes (HTLs) express:
CD4 - cluster of differentiation 4
cytotoxic T lymphocytes (CTLs) express:
CD8
what does the CD protein do?
helps us identify and distinguish lymphocytes
- functions as a co receptors during immune signaling
MHC (definition and classes)
major histocompatibility complex
MHC-I
- antigen found in all body cells except RBCs
MHC-II
- found only on antigen presenting cells
two arms of adaptive immunity
cell mediated immunity
antibody mediated immunity (aka humoral immunity)
loose function of cell mediated immunity
guards against intracellular pathogens like viruses
these are pathogens already in the tissues
loose function of antibody mediated immunity
guards against extracellular pathogens like bacteria
these are pathogens circulating in body fluids
how is a lymphocyte activated in both cell mediated and antigen mediated immunity?
antigen on an invader binds antigen receptor on a lymphocyte, activating it
clonal selection
a process in which activated lymphocytes undergo
- can produce effector cells or memory cells
- both of these will express the sam antigen receptors as the first activated lymphocyte
effector cells
a product of clonal selection once a lymphocyte has been activated
- carry out lymphocytes defence roles
- short lived
memory cells
product of clonal selection once a lymphocyte has been activated
- look for exact same antigen that triggered the clonal selection response
- longer lived
- do not actively attack
cell mediated immunity comes into play when:
when a cell is infected
in cell mediated immunity, what must infected cells do?
process and present antigens to lymphocytes
exogenous antigens
foreign molecules circulating in fluids (bacteria, worms, pollen)
how do infected cells present exogenous antigens? (5 steps)
- antigen presenting cell ingests antigen
- antigen digested into smaller parts
- cell makes MHC-II antigen and exports it to the cell surface
- foreign antigen and MHC-II fuse
- MHC-II + foreign antigen complex is inserted into the membrane to present
which body cells are antigen presenting cells
dendritic cells, macrophages, B cells
endogenous antigens
foreign antigens that are found inside of body cells
(viruses, toxins)
how do infected cells produce endogenous antigens (4 steps)
- antigen digestion
- APC makes MHC-I
- MHC-I binds antigen
- MHC-I + antigen complex is inserted into the membrane
how do Cytotoxic lymphocytes activate?
by binding the foreign antigen being displayed by the APC
the T cell then requires costimulation
costimulation
a second signal required to fully activate CTLs, secreted by helper T cells (cytokines)
cytokines
protein that stimulates division and differentiation
- in this case, in T cells
- secreted by Helper T cells
clonal selection of CTLs
effector cells
- active CD8+ T cells
- secrete perforins and granzymes
memory cells
- memory CTLs
how are Helper T cells (HTLs) activated? (3)
- HTLs bind exogenous antigen MHC-II complex displayed by an APC
- costimulation completes HTL activation
- undergoes clonal selection which produced active HTLs and memory HTLs
role of active helper T lymphocytes
- stimulate other lymphocytes by producing cytokines to costimulate CTLs
- activate B cells to stimulate antibody mediated immunity
summary of cell mediated immunity (
mediated by T lymphocytes
- CTLs recognize endogenous antigens bound to MHC-I
- produces active CTLs and memory CTLS
-
what mediates cell mediated immunity
T lymphocytes
cytoxic T lymphocytes develop from:
CD8+ cells
what do CTLs recognize to become active
endogenous antigens bound to MHC-I on APCs
APCs
antigen presenting cells
all cells that undergo clonal selection differentiate into
active attackers or memory cells
helper T cells develop from:
CD4+ cells
what do helper T lymphocytes recognize to become active
exogenous antigen bound to MHC-II on APCs
steps of lymphocyte activation (general, no specific names)
- cell is inactive
- cell meets antigen on an APC (can be endo/exogenous, and attached to MHC-I/II respectively)
- cell is active
- cell undergoes costimulation which makes them effectors or memory cells
antibody mediated immunity is mediated by;
B cells
antibody mediated immunity is when:
exogenous antigens are bound by B cell receptors
4 steps of B cell activation
- antigen is imported into B cells (endocytosis). antigen will be processed and displayed by MHC-II
- present antigen to HTLs
- HTLs now activated, release cytokines to costimulate B cells
- B cells undergo clonal selection
and produce effectors (plasma cells) or memory cells
effectors of B cells
plasma cells
- produce 2000 antibodies per second
antibodies
proteins part of teh immunoglobulin family
- 2 binding sites per
- recognizes specific protein shapes (epitopes)
epitopes
specific protein shapes
antibodies functions (3)
neutralize, agglutinate, precipitate antigens
- activate complement
- both of these lead to more efficient phagocytosis of invaders
neutralization of antigens
blocks binding sites, coats it
agglutination of antigens
clumps them up making them ineffective
what permits immunological memory
adaptive immunity
what cells help us remember past infections
memory cells
primary immune response
induced by first antigen exposure
- activation of HTLs that costimulate B cells
- phagocytes produce antibodies
secondary immune response
subsequent exposure to the same antigen
- shorter time to activate lymphocytes
- more antibodies produced
vaccines
injections or pills that contain a harmless version of a foreign antigen
- provides epitope that stimulates primary immune response so that the secondary one can come in if we get the real thing
measles
virus that causes immunological amnesia
- immune system kills virally infected cells of its own, wipes memory cells
- preventable via MMR vaccine
active immunity
during this, foreign antigen exposure
active immunity causes the body to:
make antibodies
passive immunity causes the body to:
receive antibodies
(placenta to fetus)
self recognition
the ability to recognize invaders vs self cells
makes sure that all T cells in “training” can recognize MHC-I
starts in thymus
positive selection
when T cells are permitted to continue development after being able to recognize MHC-I
self tolerance
makes sure the immune system doesnt react to its own antigens
negative selection
when T cells attack the bodies cells, and are then killed and not permitted for further development
failure of self tolerance can result in:
autoimmunity
homeostatic imbalances of the immune system
immunodeficiencies
autoimmune disorders
hypersensitivities
AIDS (acquired immunodeficiency syndrome)
- result of untreated HIV infection which infects CD4+ cells
- no cure, lots of treatments
hypersensitivity
abnormal response to foreign antigens
- eg. allergies
- produced antibodies cause mast cells to release a lot of histamine, causing anaphylaxis
