lecture 1 - antibodies, T cell receptors and MHC molecules Flashcards
what are the organisms that causes disease
pathogens
examples of pathogens
bacteria
viruses
fungi
worms
protozoa
specific/adaptive response exhibits
memory
what features allow specific immune response to have memory
- clonally distributed receptors
- large repertoire (cells have lots of different receptors)
what is the lag phase
time from infection until you get your response
lag phase in secondary response
much shorter and the number of antibodies is much higher
when a specific lymphocyte binds to a foreign antigen that lymphocyte activate and is
clonally expanded
lymphocytes are
t cells and b cells
BCR (b cell receptor) is expressed by B lymphocyte and binds to
free antigens
when the B cell is activated the BCR is released from the cell now known as an
antibody
TCR is not dimeric, what two chains does it have
an alpha and beta chain
the TCR only binds to antigens are being displayed to it by
MHC molecules
TCR is always on the T cell and never
secreted
MHCs are expressed by
APC (antigen presenting cells)
how do antibodies interact with the complement system
via the constant heavy chain regions
complement system can cause destruction of what very quickly
pathogens
how do antibodies activate effector cells
the Fc region of the antibody can be recognised by activator cells via the FcR (Fc receptor)
antibody structure:
what chains to antibodies have
2 light and 2 heavy chain
the variable domains of the two chains form the
antigen binding site
which domain does the FcR bind to
the constant region
what are the 5 antibody classes/isotypes
IgM, D, A, G and E
what region determines the class
heavy chain constant regions
light chains has 2 domains, how many can heavy chain have
4 or 5
each domain is how many amino acids
around 100
how are the domains held together
by disulphide bridge
in variable regions we have pieces that are hypervariable
in each variable region how many hypervariable regions are there
3 (HV1-3)
HV regions are the bits that are interacting with the
antigen
what part of the antigen will the antibody recognise
the epitope
a linear/continuous epitope
the parts that are bound are next to each other in primary structure
non linear epitope
parts arent close together in the primary structure but are when folded into 3D structure
antibody and antigen form what type of interactions
non covalent
what does TCR recognise on the MHC
peptide fragment of an antigen
how many domains does a TCR have
4
how many CDRs (complementary determining regions) are there in TCR
3
what does MHC stand for
major histocompatibility complex
MHC class I molecules are expressed in
nearly all cells types in the body
class I is how many chains
1
what are the subunits of the MHC class I
α1,2 and 3, β2 microglobulin
MHC class II has how many chains
2, alpha and beta chain
what are the domains in MHC class II
β1 and 2, α1 and 2
MHCs are every polymorphic which means there are many
alleles of MHC molecules
what are the 3 MHC class I molecules
HLA-A, HLA-B and HLA-C
what are the 3 MHC class II molecules
HLA-DP, HLA-DQ and HLA-DR
what cells are MHC class II molecules expressed in
APCs
the groove on MHC class II is more ____ that the groove on MHC class I
open
meaning it can bind a different array of proteins
CD8 t cells binds to which MHC class
class I MHC by CD8 binding to the alpha1/alpha2 domain
what does this binding do
stabilises TCR/MHC interaction
CD4 t cells bind to which MHC class
class II by CD4 binding to the alpha2/beta2 domains
