Immunoglobulin Structure and Function Flashcards
what are antibodies aka
immunoglobulins
where are immunoglobulins found
present in plasma, tissues, secretions and lymphatics
what are immunoglobulins a product of
humoral immune system
what are immunoglobulins secreted by
activated B cells - plasma cells
what are the 5 classes of immunoglobulin
IgM
IgA
IgD
IgE
what do immunoglobulins do
recognition function and trigger effector functions
what is antibody structure
y shaped
2 identical heavy chains and 2 identical light chains
what are the bonds between chins in antibody
disulphide bridges
what are Fab and Fc regions
Fab - fragment antigen bindig regions 2 identical
Fc - fragment crystallising region
what si the dual function go antibodies
recog function binding to antigen -Fab
effector function clearance mechanisms- interaction of Fc with effector molecules
what are the two types of light chains
lambda and kappa
what antibody classes use these light chains
all classes
what are the light chains folded into
2 globular domains termed VL and CL
what isVL and CL
VL - variable light domain at n terminus
CL - constant light domain at c terminus
what does the heavy chain determine
antibody class
what are the classes corresponding heavy chain
IgG - gamma IgA - alpha IgM - knew IgE - epsilon IgD - omega
what is the heavy chain folded into
4/5 constant globular domains VH CH1 CH2 CH3 (CH4)
what are antibodies essentially
glycoproteins
if sugars are removed what does this do to the function
no longer functions
what are the types of effector molecules
Fc receptors and complement
how do antibodies recon millions antigens
3 hypervarible loops or CDRs in each V domain revealed by comparing sequences of diff antibodies
what is CDR
complementarity determining region
what do hypervaribale and CDRs form
antigen binding site
what do CDRs form
close lying loops at one end of V domain
what does the antigen binding site consist of
when 3 in Vh and 3 in Vl are paired their 6 CDRs create binding site
what si the complementarity of antigen and bidding site
3d structures complementarity
what are the allotropes of crabon
diamond
graphite
buckminsterfulleren
what si the most abundant antibody in plasma
Ig (10mg/ml)
what is the structure of IgG
y shaped
2HC 2LC
4 subclasses
what is IgG efficient at doing
triggering complement and phagocytosis via Fc receptors
what is IgG the only Ig to do
cross placenta from mother to foetus - protect baby
what is the predominant antibody in secondary response
IgG
where is IgM found
only in plasma and secretions
too large to go into tissues
what is the structure f IgM
5 Y shaped units
joined by J chain and disulphide bridges
heavy chain has 5 globular domains
how many binding sites on IgM for antigen
10 - good at agglutining viruses
what is IgM efficient at
activating complement
what is IgM predominant for
primary response
when an infection hits what are the Ig present at primary nd secondary responses
primary - IgM
secondary - IgG
what is human IgA used in
imp serum Ig (2-3mg/ml)
what is the IgA major antibody in
saliva milk colostrum gut gent-urinary system
what is th class of antibodies encountered first by many invading bacteria and viruses
IgA
how many subclasses of IgA
2
what are the forms IgA come in
monomeric (serum) and dimeric (secretory)
how do the subclasses of IgA vary
IgA1 - O linked sugars and N linked
IgA2- all n linked sugars
what are the charateristsics of IgE
5 domains in each heavy chain
is a monomer
deco with loads n linked sugars
what is IgE effector function
interacts with recep Fc(epsilon)RI
against parcatsic infection
what is the receptor Fc(epsilon)RI
high affinity recep
expressed on mast cells and basophils
assc with allergic reactions
what is serum conc of IgD like
very low
where is IgD found
on surface of lymphocytes
whats función IgD
unclear may be involved in control antibody response
what do Fc receptors do
receptors bind sp to Fc region of immunoglobulins
what si th other effector mol
complement
do Fc receptors vary
present on many different immune cells
macrophages
neutrophils
basophils and mast cells
what can binding of antibody to FcR on immune cells cause
phagocytosis release activated oxygen sp and enzymes release inflam mediators enhance antigen presentation clear immune complexes
what are mediators of allergic response
histamine
prostaglandins
leukotrienes
