immune activation and helper cells

Question 1

properties of HLA class 2 cells

Answer 1

exogenous pathway

• found on B cells and specialised APCs
• co-dominant (maternal and paternal)
• polymorphic
• present peptides to CD4 T cells

Question 2

properties of HLA class 1

Answer 2

endogenous pathway

• found on virtually all nucleated cells
• co-dominant
• polymorphic
• present peptides to CD8 T cells

Question 3

accessory molecules

Answer 3

• adhesion
• co-stimulators
• cytokines

Question 4

describe adhesion molecules

Answer 4

due to infection and diffusion of chemotactic factors a gradient is produced towards the blood vessels and causes an up-regulation in the expression of adhesion molecules

selectin - week interaction (like velcro)

interns - strong cell-cell adhesion, holds cells together, has specific ligands

Question 5

lymphocyte activation

Answer 5

1. T cell and APC bind via an integrin molecule
2. T cell receptor then tests its CD4 against presenting antigen at MHC class 2 site
   no = detach
   yes = response will occur
3. upon recognition co-stimulator/checkpoint regulators bind and determine whether antigen responds to the T cell or not and how

Question 6

checkpoint regulators / co-stimulators

Answer 6

• pairs of surface molecules expressed in cell-cell interactions
• influence manner of response
• e.g. B7 on APC CD28 on T cells
• expressed transiently after the cells have responded in another way e.g. TCR
• modulate immune activation processes

Question 7

cytokine properties

Answer 7

• pleiotropic
  (single cytokine can act on different targets to produce different effects)
• redundant
  (more than 1 cytokine can serve the same process)
• synergistic
  (1 cytokine will affect a cell and 2nd will amplify response)
• antagonistic

Question 8

Cytokines produced predominately by activated CD4 T cells

Answer 8

1. Peptides presented by MHC class 2
2. Appropriate co-stimulators and cytokines lead to activation
3. Clone of helper cells form
4. They then have the ability to recognise other cells through their receptors and then be activated to release cytokines which modulate their activity
5. Is an adaptive response therefore antigen specific memory cells produced