Hello, my name is Judy Allen and I'm
a professor at the University of Edinburgh in Scotland.
I'm interested in the immune response to parasitic worms,
also known as helminths.
And I've become particularly interested in the role of macrophages,
both in practical terms of host defense but also in terms of their evolutionary origins.
I'd like to start with a historical perspective since it's been
a little over 100 years since Elie Metchnikoff
won the Nobel Prize for the discovery of macrophages.
And as I have been,
he was strongly influenced by evolutionary biologists and in 1893 made the statement,
"I have indeed dared to put forward a new theory of inflammation,
only because I felt that I had
Darwin's great conception as a solid foundation to build upon."
His most famous experiment which led
to his theory of inflammation was the one in which he put
a rose thorn into a transparent starfish larvae that he had found on the beach.
This is his description of the experiment and I quote,
"I fetched a few rose thorns and introduced them at once under
the skin of some beautiful starfish larvae as transparent as water.
I was too excited to sleep that night in the expectation of the result of my experiment,
and very early the next morning,
I ascertained that it had fully succeeded.
That experiment formed the basis that the phagocyte theory to
the development of which I devoted the next twenty five years of my life."
What Metchnikoff saw when he looked down
the microscope was that there was a collection of cells around the thorn.
His enormous insight was to understand that
this inflammatory response was a host defense response.
Now, people have witnessed inflammation before,
in mammals and in other systems,
but it assumed it was just damage.
They'd even even seen cells containing bacteria or yeast but thought that was accidental.
This is where Darwin's influence was so strong.
Metchnikoff thought if this very ancient primitive organism is responding
the way mammals are in terms of the influx of cells to the site of injury or infection,
this must have an important function.
Then he was really quite visionary in how he described these cells,
how macrophages could tell self from non-self,
their role in clearing bacteria and fungi,
that they were important for injury repair,
and that overall, that they had critical functions in
returning the organism to homeostasis.