Linking: Travelling to Lymphoid Tissues Flashcards
What do dcs do
Travel from site of infection to lymphoid tissue
How do activated dcs travel
Lymphatic vessel to closest lymph node
What do activated dcs express
Receptors that target them to lymphoid tissue
= leaves site infection
Describe antigen presentation = whole process gen
Activation of cd4 th and cd8 tc T cells = first antigen processed then express peptides on Mhc = 3 signals
How do apcs activate T cells
Signal 1 = pMHC:tcr, specific peptide + mhc = ACTIVATION
Signal 2 = b7:cd28 costimulatory moelcuels = SURVIVAL
Signal 3: cytokines = DIFFERENTIATION
Describe what is needed on apc to activate T cells
MHC CLASS1/2 with peptide, interact with tcr
B7.1, b7.2 = interact with cd28 on T cell
Cytokines = IL-6, 12, 23, 4
What does pamp induced prr signalling in dcs produce - initially
When activated = increase expression of receptors and adhesion molecules that targets dc to lymphatics and lymph nodes = migration
Increased processing of antigen = so can present to T cells
What does pamp induced prr signalling in dcs produce - middle, as mature
Induced expression of co stimulatory molecules (not on immature dc, signal 2 for T cell)
Increased expression of mhc molecules = increase number of mhc peptide combos (also bc higher ag processesing) = help T cells match in lymph node
What does pamp induced prr signalling in dcs produce - results
Activated dc capable of priming naive T cell (priming = first contact T cell has with ag)
Describe unactivated immature dc
Many dendrites
Can phagocytose
Cover much surface area and see if any PAMPs = find things to phagocytose
Describe activated dc in lymphatic vessel
No longer phagocytic = role change = now go to lymph node and activate T cells
Describe activated dc in lymphoid tissue
Express peptide:mhc and costim molecules
Interacts with T celll
Name the 2 types of dcs
Conventional
Plasmacytoid
Describe conventional dc
Travel to lymphoid tissue once activated
Activate T cells in secondary lymphoid organ/tissue
Classic apc
More of these than other types
Describe plasmacytoid dendritic cell
Very high levels PRRs
Stay at site infection = cannot go to secondary lymphoid organ
Secrete cytokines and can amplify local response
Describe plasmacytoid dendritic cell = produce what
Large amounts of type 1 ifn = potent antiviral cytokine, more important for clearing viral infections
Describe whole process of activated dcs travelling to lymph node
Site of infection = prr signalling —> phagocytosis and activation of dc
Activated dc = promoted to migrate to secondary lymphoid organ = lymph node
Mature dc tries to activate a specific naive T cell = find match
What causes swollen lymph node
3 signals = help T cell proliferate and activate and clonal expansion
= causes swollen lymph node
Describe othe lymphoid tissues
Peripheral = Secodnary lymphoid tissues = where cells activated = lymph node, spleen, payers patches, malt
How do dcs enter lymph node
Afferent lymphatics
How do t and B cells enter lymph node
High endothelial venules = blood circulation
What are high endothelial venules
Post capillary venules found in lymph nodes
Migration like diapedesis kinda
Describe herpes simplex virus + influenza…
Slowly kills dendritic cells when enter lymph nodes
Often when dcs transfer ag
What happens when activated dcs enter lymph node =sometimes!!!
Loaded with ag = can transfer ag to resident dcs
Can happen if antigens from viruses rapidly kill dendritic cells
What happens if no conventional dendritic cells
Tissue resident = in skin, macrophages with dc morphology = lc = langerhans cells are responsible for initial uptake and transport and can transfer antigen to resident dcs
TRUE OR FALSE Langerhans cells cannot stimulate naive T cells
FALSE
Both can stimulate naive T cells
Describe naive lymphocytes
Constantly travel = after developed, leaves and travel
Constantly scan for specific ag that they can respond to, want to find match
Spend hours in Secondary lymphoid organs
What happens if T cells do not encounter antigen
Exit and return to blood to restart search
Leaves via efferent lymphatics
What happens if T cell finds match
= will stay in lymph node
What happens to T cell in lymph node after finding match
Gets 3 signals
= T cell activated, proliferates, differentiates
Takes time and is trapped in lymph node until proliferation is complete
What happens to effector T cells
Exit lymph node via efferent lymphatics
Home to infected tissues (chemokines receptors and adhesion molecules lead them to site fo infection)
