BCR and B cell Devo Flashcards
The arm of the Adaptive immune system that fnxs to combat extracellular pathagens and toxins
Humoral Immunity
The humoral immune response are activated by and recognize?
Proteins, polysaccs, lipids, small chemicals
How do antibodies fnx?
Block microbes or their toxins from binding to and infecting host cells. Also limit infection of intracellular pathogens
Defects here result in increased suspecitbility to viral, bacterial and parasitic infection
Antibody production
Antibodies recognize _________ alone and T cells need presentation by_______
Antigen
APC
What make up TCR and BCR complexes?
antigen receptors and attached signaling proteins
Signally requires binding of ______
two or more membrane Ig’s (BCR)
What forms of antigens to antibodies recognize?
Macromoleucles like proteins. polysachs, lipids, nucleic acids, conformational and linear epitopes
Where do AntiB’s get diversity?
each clone has unique specificty and potential for over 1000000000 specificities
What mediates signal fnx of antibodies?
Ig alpha and Ig Betta associated w/ membrane Ig
Effector regions are mediated by?
Constant regions of secreated Ig
What restricts TCR recognition?
MHC I or II
What mades up antiG binding regions of Ig’s?
3 CDRs in Vh and three CDRs in VL
What is special about constant regions of BCRs?
They can change: called class switching and is done in the Heavy Chain; will switch from membrane bound to secreated form
If affinity of antiG binding strong or weak for Ig?
Does it change?
STRONG… more neg KD is stronger it is
Has stronger initial affinity and increases strength w/ response
Does TCR affinity get stronger/weaker/fixed?
fixed
Which receptor only recognizes antiG in context of peptide and MHC?
TCR
Which receptor can recognize numerous chem structures: proteins/lipids, ect?
BCR
What kind of forms do BCR come in?
Bound and secreated
Where are TCR located?
membrane localized
These receptors are made of heavy and light chain proteins?
BCR’s
These guys are made of alpha and beta chains?
TCR
During Early lymphocyte devo: you can become either B cells or T cells:
B cells will express________
T cells wil express_________
heavy chain protein expression
TRC beta chain protein expression
What is our mitogenic signal for devo’in lymphocytes (both B and T) to proliferate?
IL7
IL7 is made by?
bone marrow stromal cells
After a Pro B cell is exposed to IL-7 and proliferates, B cell will express what?
one chain of antiG receptor: the Ig heavy chain and is now a Pre-B cell
After 2nd exposture to IL-7 what does the B cell do?
Expresses complete antiG receptor, proliferates and has weak antiG recognition
What are the three gene segments that recombine during cellular differentiation and maturation of B cells?
V(variable) D(Diversity) and J(joining)
What is our first recombination event?
heavy chain D and J exons to DJ
What is our second recombination event?
V combines with DJ
VDJ recomibination of Ig H C______ region gene segment (first Constant region)
Mew
What makes up a heavy chain transcript and where does it need to be expressed to get past first checkpoint?
VDJC and needs to be intact on cell surface with a surrogate light chain
How is light chain made?
V and J come together then join light Cmew segment to make up transrcript for Ig Light chain
What is required at our second checkpoint?
Have recombinded H chain and C mew which is now collectively makes up Ig M
What is our B cell called at second checkpoint?
Immature B cell
Order of B cell maturity
Stem cell–> Pro B–> Pre-B–> Immature B–> Naive Mature B
Where do Mature B cells go?
To peripheral immune tissues such as spleen or lymph nodes. Haveen’t met their antiG yet
What Ig’s do a mature B cell express?
Ig G and Ig M
What confers antiG specificity on an antiBody
the dimeric protein of the BCR
Difference btwn T and B cell binding site it?
T cell has one binding site or groove
B cell has 2 identical binding sites that see same epitope/antiG
What is Fab region of antiB?
its our variable region that recongizes diverse antiG
made of light and heavy chain
What makes up stalk of antiB
Fc region = constant region, also has complement binding sites
how many different constant regions are there in B cells?
Up to 9 dif constant regions
Where is D region expressed?
only inIg Heavy chain
In the Junctional region, which enZ adds NT?
TdT enZ
What are the two mechanisms for antiG Diversity?
Combinatorial and Junctional
method that results in variation amongst possible V-D-J and VJ exon combinations
Combinatoral
method that involves removal of NTs, adds NT via TdT and has strand repair during recombination process
Junctional
Each variable region of Ig H and Ig L have 3 regions of HYPERavailability known as:
CDR: CD1, CD2, CD3
