Let's look at the
natural killer cell.
The previous talk, I again, like in
these to a deranged person with an AK-47.
If natural killer cells don't
see an appropriate self-antigen,
a friendly face, they will fire.
So, why do we have NK cells?
Well, they are important for
immunity to intracellular pathogens.
And we have an example here of a
virus infected cell at the bottom
that is no longer expressing
The loss of those inhibitory receptors,
because of the viral infection
will cause the mast cell to sidle
up next to that cell and to kill it.
Mast cells also have on
their surface Fc receptors.
So they recognize the constant fret
constant region fragment of bound antibody.
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.
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.
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.
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.
That natural killer cells
also make cytokines.
So they are going to be important for
driving the stimulation of other cells.
This is all kind of
trying to recruit
a big inflammatory army that can
deal with potential infections.
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.
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.