In adaptive immunity, cytokines are
going to be very important mediators.
So I've used the
term a couple times,
let's just describe
what these really are.
So they are made by a
variety of cell types,
but I'm going to emphasise the ones
here made by CD4 helper T cells,
since that's their major
job making cytokines.
The first cytokine that is made
usually after interaction with
an antigen presenting cell,
showing displaying a foreign
peptide is Interleukin-2 or IL-2.
IL-2 is very important because it
causes clonal expansion of that T cell,
a single T cell can't do very much, you
need a clonal army to deal with infections.
So the very first cytokine
that's made is IL-2,
which in that local environment
will drive in an autocrine pathway,
a feedback loop.
It will drive the proliferation
of the responding T cells,
so we get more and
more and more of them.
That's a good thing because we
need a clonal army to do it's job.
That clonal army will
also make other cytokines
such as interferon gamma.
Interferon gamma has
a variety of effects.
But the most important one
for this discussion right now
is the activation
We will turn macrophages
from someone who looks like me into
Arnold Schwarzenegger at his peak,
so they become much
more aggressive killers,
and they will do
their job better.
Other cytokines that are produced
by the activated T helper cell
include those that will drive
specific B cell activation
and will lead to the elaboration
of specific isotypes.
So those T cells,
the helper T cells in our clonal army
are going to make
interferon gamma, interleukin-5,
all of which will affect
B cells and tell them which antibodies
are going to be most important.
In addition, cytokines,
such as interleukin-2 and interferon gamma
will drive the activation
of cytotoxic T lymphocytes.
So I hope you're getting the
idea that the helper T cell
through the elaboration
of a variety of cytokines
can drive a whole
bunch of both innate
and adaptive immune responses.
So in words, kind of what I've just
said in the figure form on the right.
These cytokines are made
by CD4 helper T cells.
It's important to also understand
that cytokines can be made by
CDA positive cytotoxic T cells
or by natural killer
cells or by macrophages.
So, there are a variety of cytokines
made by different cell types.
Those cytokines will activate cells
of innate and adaptive immunity.
And they will regulate B cell isotype
selection and B cell proliferation,
the activation and proliferation
of cytotoxic T lymphocytes,
the activation of macrophages,
of NK cells, of endothelial cells etc.
So, there are a tonne of effects
related to these protein mediators
coming out of an
activated T cell.
Most important T cell
for these CD4-positive,
although other cell
types can do it.
And with that, we've concluded a brief
run through of adaptive immunity.