The chemokines are chemotactic cytokines, but
they have multiple other effects as well.
And they are secreted by
many different types of cell.
There are four families that are grouped according
to the arrangement of cysteines in their structure.
The C family chemokines, an
example would be lymphotactin.
CC family, an example would be
RANTES, CXC - interleukin-8.
And you can see here an example of the fact that things
don’t often fit neatly into the little boxes we’d
like, because interleukin-8 is both an interleukin,
obviously that’s its name, but it’s also a chemokine.
And then finally the CX3C chemokines, and fractalkine
would be an example of that particular family.
So each family has a number of members and I’m
just highlighting one example for each one.
The tumor necrosis factors, there are two main types
- TNF alpha (α) and TNF beta (β) (lymphotoxin).
This is actually another good example, there
are mul-- I’m afraid there are multiple
examples in immunology of things that
actually, their name isn’t great okay?
So you would imagine from the name that these factors are
really good at inducing necrotic cell death of tumor cells.
Well, they can do that, you know.
But if they were so magnificent at
doing that, you’d expect that we’d be
using TNF to treat lots and lots of
tumors, and that’s simply not the case.
It’s named because that was the
first activity when it was first
discovered, it was found that it could
cause necrotic cell death of tumors.
It’s actually better at causing apoptotic
cell death of tumors than causing necrosis.
And in fact, it’s not particularly
good at doing either of those things.
It’s an inflammatory cytokine, that’s what its
main function is, to promote inflammation.
And the two main TNFs, TNFα and TNFβ
are produced by multiple cell types
including macrophages, monocytes, T-cells,
B-cells and natural killer cells.
And there are many different things that these TNFs do, they
can activate macrophages, they’re good an inducing endothelial
cell adhesion molecules in acute inflammation, and they’re
good at stimulating the production of other cytokines.
Transforming growth factors; the main
one that is of importance in immunology
is transforming growth factor β, which
is mainly an inhibitory cytokine.
Secreted by regulatory T-cells and also
by monocytes, it inhibits macrophage
and dendritic cell activation, and can
also inhibit both T and B-lymphocytes.