Immunoglobulins Flashcards
how were antibodies discovered
Found that plasma contained something that was anti-toxin
Tiselius separated serum by gel electrophoresis and found that the gamma fraction of his gel contained antibodies that could bind antigens
what are the two functionally distinct fragments of antibodies and their function
Fragment antigen-binding (Fab): antigen binding
Fragment crystallizable (Fc): effector function
what enzyme cleaves the hinge region of immunoglobulins
pepsin
how were heavy and light chains of antibodies discovered
using reducing agent to break down the chemical bonds in the structure rather than the protein structure
which regions allows unique specificity between individual antibodies and why
hypervariable loops of the variable region in the Fab region due to hypervariability is certain parts of the primary amino acid sequences
what is a CDR
how many are there in each chain and in each variable region of an Ig
how do they function
complementarity determining region
3 on the heavy chain and 3 on the light chain
separated in the sequence but in a 3D structure are near each other forming a grabbing bowl structure that recognises antigens
which cells of the immune system express Fc receptors (receptors for antibodies)
macrophages
dendritic cells
mast cells and eosinophils
NK cells
which immune molecules can bind antibodies
complement molecules
5 immunoglobulin isotypes and summary
IgM (μ - mu): pentamer, found in breast milk
IgD (δ - delta): provide differentiation of B-cells
IgG (γ - gamma): can cross the placenta, greatest concentration
IgE ( ε - epsilon): involved in allergic reactions, control commensal microbes
IgA (α - alpha): present in secretions, dimer
which is the first type of immunoglobulin to develop as B-cell receptors
IgM
why do babies have a disease susceptible period at ~4 months old
transient low IgG levels
IgG levels from mother decrease then baby starts to make its own IgG
what dictates the different subclasses of IgG
what are each of their functions
they have differences in the number of disulphide bonds
IgG1/3 bind toxins
IgG2 bind surface of pathogens (polysaccharides)
IgG4 are present in levels during allergic reaction
what are the functions of antibodies
neutralisation of pathogens and toxins
opsonisation of pathogens
recruitment of complement
antibody dependent cellular cytotoxicity - ADCC
degranulation of mast cells and eosinophils
explain neutralisation of viruses/bacteria/toxins
which Ig isotypes are responsible
antibodies bind to surface receptors of pathogen or the toxin itself and block binding
IgA and IgG
how do IgA molecules control levels of commensal microbiota
they have a low affinity system for them, only have high activity if there are too many
