Lectures 1&2 - Immunology overview and polypeptide chains of antibodies Flashcards
which two cells is specific/acquired immunity mainly mediated by?
B and T cells
what is secreted when a B cell is activated?
anitbodies
what do the C regions of an antibody react with ?
complement /FC receptors
what are the V regions of an antibody specific to?
an antigen
which chain in an antibody determines the isotype?
heavy
which chain of an antibody has 2 domains? what are they?
light chain has 2 domains
lamda and kappa
what 4 types of antigens can antibodies recognise?
peptide, carbohydrate, lipid and nucleic acid
how many hypervariable regions does an antibody have in total?
how many in each of the light and heavy chain?
6 in total
3 from light, 3 from heavy chain
what does Fab stand for? (antibodies)
fragment antigen binding (variable region)
what does Fc stand for? (antibodies)
fragment crystallisable (constant region)
what type of family do antibodies, MHC molecules and T cell receptors belong to?
glycoprotein family
T cells express a T cell receptor which recognizes the……… fragment of an antigen, bound to a ……. molecule
peptide fragment
MHC molecule
class 1 MHC molecules are expressed on which cells?
all nucleated cells
class 2 MHC molecules are expressed on which cells?
antigen presenting cells/APCs
which 3 genes do class 1 MHC have?
HLA, HLB, HLC
which 3 genes do class 2 MHC have?
HLA DP, HLA DQ, HLA DR
which type of T cells do MHC class 1 recognise?
cytotoxic CD8+
which type of T cells do MHC class 2 recognise?
CD4+
in the H chain of antibodies and the TCR beta receptors, which 3 gene segments encode the V region?
V, D, J
in the L chain of antibodies and the TCR alpha receptors, which 2 gene segments encode the V region?
V and J
in H chain recombination which 3 gene segments are joined together?
V, D and J
In H chain recombination what is the order of joining of the V, D and J segments? (2 steps)
1) D to J
2) V- DJ
in L chain recombination, the V and J gene segments are joined. Does it happen in the kappa or lamda chain initially?
what happens if this chain is unsuccessful in recombination?
kappa
if unsuccessful, then lamda segments are recombined
on which chromosomes are these chains found (antibodies)? :
- H chain
- Kappa light chain
- Lamda light chain
H chain on chromosome 14
kappa light chain on chromosome 2
lamda light chain on chromosome 22
the heavy chain for an antibody is C-mew / Cu. What is its class/epitope?
IgM
what do the recombination activating genes 1 and 2 (RAG-1,2) encode for, involved in Ig gene segment rearrangement)?
lymphoid specific components of VDJ recombinase
what do mutations in RAG genes lead to?
immunodeficiency
can B cells express both the kappa and lamda rearrangements?
no, either one or the other
imprecise joining are differences in sequences where which two gene segments join?
V-D and D-J
what are N regions, creating junctional diversity, a random addition of at V-D and D-J junctions?
nucleotides
random nucleotide addition at V-D and D-J segments is done by which enzyme?
terminal transferase
where does somatic hypermutation occur in antibodies?
germinal centres
in which genes of antibodies is mutation frequency the highest?
VH/VL (V) genes
what is the function of AID enzyme? (hint: deamination of one base to another)
what does it lead to?
acts on DNA to deaminate cytosine to uracil
mutations
class switching of antibodies is done in which chain?
heavy
why is IgM the first class of antibody to be expressed in a developing B cell at the heavy chain locus?
in the heavy chain locus, C-mew/Cu is the closest segment to the VDJ gene segments
how many transmembrane domains do MHC class 1 and MHC class 2 molecules have respectively?
MHC 1 = 1
MHC 2 = 2
which MHC molecule binds smaller amino acid chains? how long are the chains which each MHC class bind?
MHC 1 binds smaller - 8-10 AAs
MHC 2 binds larger - 13+ AAs
what does HLA stand for?
human leukocytic antigen
true or false, TCRs can only recognise peptides as opposed to antibodies which can recognise peptides, carbs, lipids and NAs?
true, they can only recognise peptides
which chain of MHC class 1 molecules doesn’t bind to the associated peptide?
beta - 2 microglobulin
it is the alpha chain which binds the peptide
How are the heavy (H) chain of an antibody and the beta
(b) chain of the TCR similar?
both only involve the V and J segments for recombination
WHEN does rearrangement of Ig genes occur?
early stages of B cell development
There are 5 distinct mechanisms that allow for antibody
diversity; list them?
which mechanism involves the addition of nucleotides by terminal transferase?
which mechanism involves AID enzyme?
1) VDJ recombination
2) SHM (AID enzyme)
3) junctional diversity (nucleotides added by TT)
4) class switching
5) combinatorial diversity
