00:01
Let's look at the
natural killer cell.
00:03
The previous talk, I again, like in
these to a deranged person with an AK-47.
00:09
If natural killer cells don't
see an appropriate self-antigen,
a friendly face, they will fire.
00:18
So, why do we have NK cells?
Well, they are important for
immunity to intracellular pathogens.
00:27
And we have an example here of a
virus infected cell at the bottom
that is no longer expressing
inhibitory receptors.
00:37
The loss of those inhibitory receptors,
because of the viral infection
will cause the natural killer cell to sidle
up next to that cell and to kill it.
00:45
Natural killer cells also have on
their surface Fc receptors.
00:48
So they recognize the constant fret
constant region fragment of bound antibody.
00:55
And so, if antibody is bound
to a particular target,
they will come up bind with
their Fc receptors and kill,
this is called antibody-dependent
cell mediated cytotoxicity or ADCC
as you see on the screen there,
They kill just like
a cytotoxic T cell.
01:11
So they have within
them preformed granules
that contain porphyrin,
which is a pore-forming protein,
and granzymes, which will activate
the intrinsic apoptosis pathways.
01:24
So when they form their
synapse, when they bind,
either through Fc receptor
and an antibody recognition,
or through that loss of
the inhibitory receptors.
01:34
They will release porphyrin
in a directorial fashion,
punch a hole,
and then granzyme will go across
and will cause the death
of the target cell.
01:45
That natural killer cells
also make cytokines.
01:50
So they are going to be important for
driving the stimulation of other cells.
01:55
This is all kind of
trying to recruit
a big inflammatory army that can
deal with potential infections.
02:01
So here we see a macrophage
talking to an NK cell,
the macrophage is going to make
Interleukin-12 that's IL-12,
that will activate the NK cell and
make it a more robust responding cell.
02:14
At the same time, that NK cell
is going to make interferon gamma
which will drive the activation of
the interferon gamma macrophages
and make them
better at their job.