Immunoglobulins Flashcards
Antigen definition
any substance which elicits an immune response
which portion of an antigen is recognised by antibodies
epitopes (antigenic determinant)
each antigen can have many epitopes
where are immunoglobulins present
what type of cells secrete them
plasma, tissues, secretions and lymphatic system
activated B cells
what are the five classes of immunoglobulins
IgG - gamma
IgA - alpha
IgM - mew
IgE - epsilon
IgD - delta
“gamed”
what are the chains of an immunoglobulin?
variable heavy
variable light
constant heavy
constant light
what are the two fragments of an immunoglobulin and their functions
Fragment antigen binding (Fab) - responsible for recognising and binding antigens
Fragment crystallisable (Fc) - responsible for effector function/interacts with effector molecules
which enzyme cleaves
papain
what are the two types of light chains in immunoglobulins
lambda
kappa
where and by what are immunoglobulins glycosylated
in the gap in the CH2 domain of the Fc region
by n-linked oligosaccharides attached to asparagine (Asn) residues
how can millions of different antigens have a small number of effector molecules
antibodies work as adapter molecules
i.e. unique Fab region but Fc region interacts with the same effector molecules as other antibodies
how does the antigen system recognise millions of different antigens?
three hypervariable loops or CDRs in each variable domain
CDR = complementarity determining region
how do hypervariable loops or CDRs form the antigen-binding site
CDRs are found on the loops between beta-sheets
when the VH and VL chains come together their 6 CDRs lie close together in 3D space
what type of chemical interactions do antibodies bind antigens with
non-covalent
which Ig subclass is most abundant in plasma (10 mg/ml)
IgG
which Ig subclasses trigger complement
IgG and IgM
