Major Histocompatibility Complex Flashcards
In adaptive immune system, for appropriate response to a foreign antigen what must happen?
- lymphocytes must recognise antigen
- stimulated to divide and differentiate
What are T cells is mediated by and what can they recognise only?
- T cells is mediated by T cell receptor (TCR)
- T cells only recognise parts of antigens that are expressed on our own cell surfaces. so not on viruses
What is the B cell antigen-recognition molecules?
immunoglobulins
What are the 2 ways antigens can be derived?
- pathogens that replicate within host cells e.g. viruses or intracellular bacteria
- pathogens or their products that have been endocytosed from the extracellular fluid
No matter what way antigens are derived what is always displayed on their cell surface?
In both cases, cells display on their surface peptide fragments derived from the pathogen’s proteins
What are Pathogen-derived peptides delivered to and presented at cell surface by?
specialized glycoproteins known as Major Histocompatibility Complex (MHC) molecules
What are MHC encoded by?
MHC proteins are encoded in large cluster of genes on chromosome 6
What combination do T cells recognise?
T cells recognise combination of MHC molecule and small peptide fragment of antigen
What are the 2 MHC families and what are each families members?
Class I - HLA-A, HLA-B, and HLA-C
Class II - HLA-DP, HLA-DQ, and HLA-DR
Where is the MHC families Class I and Class II expressed?
Class I - expressed on all nucleated cells including leucocytes
Class II -expressed only on leucocytes which present antigen to T cells e.g. monocytes
Class I and Class II have related 3D-structures but different subunits, which one has a more open peptide-binding cleft?
peptide-binding cleft is more open that in MHC Class I
T cells only see antigen in association with MHC proteins.
What type of T cell does each MHC Class present antigenic peptides to?
- MHC Class I present peptides to TC cells
- MHC Class II present peptides to TH cells
