L19: Immunology and Pregnancy Flashcards
What does allogeneic mean?
Genetically different
What does syngeneic mean?
Genetically identical
What are the mechanisms of transplant rejection?
- T cells - T helper (Th) cells and Cytotoxic T Lymphocytes (CTLs)
- antibodies
- NK cells
- innate effector cells - macrophages, neutrophils etc
What are the two immune system arms?
Innate and adaptive
What describes innate immune system? What are the example cells?
- cells and molecules that recognise ‘danger’ - pathogens or damage and kill immediately
- examples: NK cells, macrophages, neutrophils, complement
What describes adaptive immune system? what are the example cells?
- cells that recognise ‘non-self’
- require the innate immune system for activation
- slow at first encounter (primary response), but has ‘memory’ - can respond much faster and more effectively on subsequent exposures (secondary response)
- examples: T and B cells, antibody
What describes B cell receptor?
- recognise soluble antigen
- produce antibodies and have antigen-specific receptors
- antigen-binding region made in an entirely random way
- each B cell has a unique specificity
What is negative selection of B cells?
During development those random antigen specific receptors that bind to self-antigens are deleted/killed - negative selection
What happens when antigen-specific B cells are activated?
They produce antibody - soluble version of the BcR, binds to pathogens/foreign tissue - targets them for killing
How does T cell antigen recognition work?
- T cell receptor (TcR) analogous to antigen-binding region of an antibody/BcR - BUT CANNOT bind soluble antigen directly
- antigen peptides must be presented on MHC molecules
- TcR binds both self-MHC and foreign peptide
What is negative selection of T cells?
During development those random antigen specific receptors that bind to self-antigens are deleted/killed - negative selection
What is positive selection of T cells?
- T cells must also recognise ‘self’ MHC
- T cells with random receptors which do not bind to self MHC also deleted/killed – positive selection
What’s the function of MHC molecules?
The function of MHC molecules is to bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells.
What are the two classes of MHC? What are their differences?
- Class I MHC present intracellular antigens to Cytotoxic T Lymphocytes (CTLs)
- Class II MHC present extracellular antigens to helper T cells
Where can MHCI be found?
on all nucleated cells (not red blood cells) except for neurons
Where can MHCII be found?
only on specialised ‘antigen presenting cells’ eg dendritic cells, macrophages
What are naive T cells? what do naive T cells differentiate to?
- T helper cells which have not yet seen their specific antigen (on MHCII) are termed ‘naive’
- naive T helper cells, when activated, will differentiate into TH1, TH2 or Treg
- which subset they differentiate into depends on signals from the innate immune system
What are Th1 cells?
Inflammatory, good for killing bacteria, but can cause tissue damage/autoimmunity/transplant rejection
What are Th2 cells?
- kill parasites, and can cause allergy - much less damaging and inflammatory