0:00
Hello. My name is
Bruno Silva-Santos.
I'm a Professor of Immunology
at the Medical School
of the University of
Lisbon in Portugal.
I'll be lecturing on γδ T cells.
0:14
Until the mid-1980s, lymphocytes
were thought to be either
B cells or T cells,
and in this case, αβ T cells,
meaning cells expressing
a T cell receptor
composed of an α and a β chain.
But in 1984, γδ T cells
joined this lymphocyte family
and were characterised
as expressing a different
antigen receptor.
This antigen receptor was
composed of a γ and a δ chain
and was shown to bind
very different ligands
compared to their αβ
T cell counterparts.
0:54
Actually, γδ T
cells were shown to
be conserved
throughout evolution,
ever since the emergence
of jawed vertebrates
450 million years ago,
essentially with the shark.
Throughout evolution, all
the other organisms that
you can see in this
picture actually
contain γδ T cells
besides αβ and B cells.
This trio of lymphocytes
has been conserved
throughout evolution.
1:25
γδ T cells are defined
by the expression
of the TCRγ and TCRδ chain
that paired together
to constitute the
γδ T cell receptor.
This is something that
around 1-2% of T cells do,
both in mice and humans.
As you can see in the
human blood FACS plot,
we have around 2% of leukocytes
expressing this γδ
t cell receptor.
This is in the human blood,
it can be very different
in some mucosal surfaces,
like the intestine,
where γδ T cells can
account for up to 30%
of the lymphocytes that
live in those surfaces.
They are expressed by
γδ T cell receptor
and what's very peculiar about
this γδ T cell receptor,
is that it does not
respect the rule of
the conventional T cell
receptor of binding
the MHC presenting molecule.
