My name is Paul Fairchild and I'm based at the Sir William Dunn School of
Pathology in Oxford and I'm a fellow of Trinity College in Oxford as well.
What I want to do in this lecture is to
introduce you to the whole field of hematopoiesis.
Now, hematopoiesis is of course quite an ugly word,
but it's actually derived from two Greek words.
The word heme on the one hand,
which refers, of course,
to blood and the verb poeio,
which means making or to make something.
Hematopoiesis actually means the making of the entire blood system.
Hematopoiesis is extremely important to us because without an understanding of
hematopoiesis we cannot really understand the way in which the immune system works.
But hematopoiesis is also important because it is by far and away
the best understood of all systems of
differentiation from a dedicated population of stem cells,
the so-called hematopoietic stem cells.
Now the concept of the hematopoietic stem cell
can actually be traced back more than a century.
But it was actually in 1961 that
the first unequivocal evidence for
the existence of the hematopoietic stem cell was published.
This was the work of a pair of scientists,
James Till and Ernest McCulloch.
What they did was to derive a particular assay,
an in vivo assay of hematopoiesis,
which is actually still used widely today throughout the world.
What they did was to take an adult mouse and to
expose it to high levels of ionizing radiation,
a lethal dose of radiation in fact.
But they then rescue that mouse from lethality by
the injection of bone marrow derived from a non-irradiated adult.
What they found was that those bone marrow cells were able to
repopulate the entire blood system and immune system of the recipient.
By using some clever tracking or tracing methods,
they were able to show that a single cell could give rise to
many different cell types as distinct as the neutrophil,
lymphocyte, monocyte, basophil and eosinophil,
as well as the actual erythrocytes and platelets that make up the blood system.
That was the first unequivocal demonstration
of the existence of the hematopoietic stem cell.
In fact, many studies and much of our understanding of
hematopoiesis actually comes from those early seminal studies by Till and McCulloch.