Flashcards in B effector functions Deck (114)
What type of protein are immunoglobulins?
What is an antibody?
protein produced in response to an antigen that binds specficially to that antigen
What are the secondary effector functions of antibodies?
complement activation; opsonisation; cell activation via Fc receptors
What are the 2 general functions of antibodies?
bind specifically to the pathogen or its products that have elicited the immune response; recruit other cells and molecules to destroy the pathogen once the antibody is bound
What are the types of the constant region on antibodies known as?
What is avidity?
total strength of interactions on an antibody- multiple interactions bewteen an antibody with multiple binding sites and a complex antigen with multiple epitopes
What is affinity?
strength of the interaction between a single antigen binding site and its antigen
What are the 2 forms of light chain?
lambda and kappa
What part of the natibody confers the functional effector properties of the different classes of antibody?
the carboxy-terminal part of the heavy chain which isn't connected to the light chain
What is the difference in structure between the BCR and an antibody?
in the BCR the carboxy-terminal is a hydrophobic amino acids to anchor molecule in membrane, whereas the terminus its a hydrophilic sequence to allow secretion
What is the immunoglobulin domain?
repeats found in each heavy and light chain of a series of amino acids sequences which correspond to a discrete, compactly folded region of protein
How many Ig domains does a light chain have?
How many Ig domains does a heavy chain have?
What is the structure of each V or C domain in an antibody?
-immunoglobulin fold: 2 beta sheets built from several beta strands, which are folded onto each otehr to form a beta sandwich
What bonds hold the immunoglobulin fold together?
backbone hydrogen bonds between adjacent strands ; covalent link by disulfide bond between cysteine residues on each sheet
What is the main difference in structure between V and C domains on an antibody?
V domain is larger and contains extra beta strands
What joins the 2 arms of the immunoglobulin to the trunk?
flexible atretch of polypeptide chain- hinge region
What is the effect of papain on an immunoglobulin?
cuts the amino-terminal side of the disuflide bond that links the heavy chains together
What is attached to the CH2 domains of the immunoglobulin?
What is the effect of pepsin on the immunoglobulin?
cuts the carboxy-terminal side of the disulfide bond linking the heavy chains- leaving a F(ab')2 fragment and the other heavy chain into small fragments
What is the F(ab')2 fragment?
both antigen binding arms of the antibody are liinked
What is F(ab')2 fragment written with a prime?
it conts a few more amino acids than Fab including the cysteins that form the disulfide bonds
What is significant about the hinge region of immunoglobulins?
allows some degree of independent movement of hte 2 Fab arms
What is the hinge region of the Ig also known as?
molecular ball and socket joint
Where else is there flexibility of movement in the antibody molecule?
between the V and C regions
What is the function of flexibility at the hinge and V-C junction?
allows 2 arms of the antibody to bind to sites some distances apart e.g repeating sites of bacterial cell walls
How many polypeptide chains is the IgG antibody made up of?
What is the purpose of having 2 antigen binding sites on an antibody?
antibody molecules can cross-link antigens and bind much more stably and with higher avidity
Is sequence variaiblity distributed evenly thoughout the V regions of the antibody?
no- concentrated in certain segments: hypervariable regions