Hello and welcome to this Henry Stewart Talk on the immune system.
I'm Geoff Hale and today I plan to tell you a bit about
the development and use of antibodies for treating a wide range of diseases,
starting right back in the 19th century and coming up to the present day.
First of all, just a little bit of recap about the antibody structure and what they are.
You'll remember that antibodies have got
two binding sites that comprise of two different chains,
the heavy chain and the light chain.
At the end of the heavy chain,
you've got the Fc region,
which is responsible for binding to molecules in the immune system,
that calls the effector function of the antibodies.
Normally antibodies circulate around the body in
large quantities and they are comparatively inert.
But when they encounter a pathogen,
say it's a bacterium or a virus,
they can bind to antigens on its surface
and that causes aggregation of the antibody Fc domains.
That greatly increases the affinity of their binding to complements or to
Fc receptors and it leads to activation of those physiological effector functions.
Aggregation of antibodies is a really important part of their function.
There's some key properties of antibodies which are
really important for using them in therapy.
First of all, their binding function.
They are exquisitely specific to their target and that makes them
really useful because they don't target unwanted things usually.
Because they've got two binding sites,
they can hang on to antigens really tightly.
That is what we call avidity.
Then the effector function, as I've mentioned,
antibodies can activate complements,
they combine Fc receptors and that can lead to killing of cells and targets,
whether they're viruses or bacteria.
Thirdly, antibodies have a long half-life in the blood.
That's because they bind to another type of
Fc receptor called FcRN found in the liver and other cells.
It enables the antibody to be recycled back into
the circulation so that it survives perhaps for a month on average,
very useful feature if you use antibodies as drugs
because it means they don't have to be administered very frequently.
But antibodies are different from conventional drugs.