Dendritic cells Flashcards
What is the main role of dendritic cells ?
they play a key role in initiating the adaptive immune response
What happens when adaptive immunity goes wrong ?
it can turn against our own cells causing autoimmune diseases
What is periscoping ?
when dendritic cells push themselves between cells which protrude into the local tissue environment e.g. gut lumen, skin and airways
Why do dendritic cells carry out periscoping ?
- dendritic cells are primarily tissue resident cells
- they are constantly sampling blood and micro environment for antigens and pathogens but also food and stress hormones
- all of these things link to the immune response
Describe the function of dendritic cells
- dendritic cells play an important role in the initiation of antigen specific reactivity by activating the B and T lymphocytes in the lymph nodes and educating them to mount an appropriate immune response
- the distribution, migration, maturation and antigen presentation properties of these cells allow this to happen
Describe what happens when dendritic cells detect pathogens
1) immature dendritic cells sample the airway to detect pathogens and carry out phagocytosis
2) dendritic cells travels down the afferent lymphatic vessels into the lymph node where they enter the paracortex and present the antigens on the T lymphocyte
3) the T lymphocyte then undergoes expansion and differentiation into an effector T cell
4) the effector T cell will leave the lymph node via the efferent lymphatic vessel and enter the systemic circulation following a chemokine gradient back to the lungs
5) it will then leave the vessel via the lung capillary bed and migrate towards the pathogen to clear it
6) during this process it develops immune memory
Which receptors are found on the surface of dendritic cells ?
Dendritic cells are covered in receptors
- costimulatory receptors are involved in the activation of T cells by producing signals
- cytokine and chemokine receptors are present so the dendritic cell can respond to stimuli
- solute transporters allow things like glucose to enter the cell
- adhesion molecules are involved in allowing the T cell to bind during activation
What is the difference between immature and mature dendritic cells ?
Immature = dendritic cell in tissue but hasn’t encountered a pathogen
Mature = activated dendritic cell after encountering antigen or pathogen etc
What changes will the dendritic cell undergo as it matures ?
- increase in costimulatory molecules
- increase in MHC II expression
- increase in the secretion of proinflammatory cytokines
- decrease in phagocytic capacity
- increase in CCR7 expression
- increase in glycolytic ability
What is the role of the CCR7 receptor on dendritic cells ?
CCR7 receptor allows the dendritic cell to respond to 2 key chemokines that are produced by the lymph organs
- CCL19
- CCL21
Describe the importance of CCL19 and CCL21
- they have different effects but are both needed for the optimum dendritic cell activation
- CCL19 carries out more chemotaxis, internalisation and beta arrestin than CCL21
- CCL21 does more phosphorylation of ERK1/2 than CCL19
What must dendritic cells do in order to activate T cells ?
They must carry out 3 signals and these occur in order
What is MHC ?
- major histocompatibility complex
- located on the short arm of chromosome 6
- there are 2 classes : class I and class II
Summarise the properties of MHC class I
- presents endogenous peptides and intracellular pathogens
- presents to CD8+ T cells
Summarise the properties of MHC class II
- presents exogenous peptides and extracellular pathogens
- presents to CD4+ T cells
