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My name is Herman Waldmann,
I'm from the Department of Pathology, Oxford University.
I'm going to be introducing this course on immunology.
Very timely, given the pandemic we have,
that people understand what the immune system can do and what it can't do.
The immune system is complicated,
but its main role is to sense and eliminate dangerous microbes and then enable healing.
It has to do this without causing lasting damage to the host.
The cells that participate in this immunity are blood cells and a variety of proteins.
The blood cells are able to migrate around the body,
which makes them able to go anywhere where danger is operating.
Because the cells are circulating around the body,
they also provide a tremendous asset to
cell biologists who can look at single-cell function instead of tissue function.
The way the immune system is organised is first of all,
to sense that something is there,
that it shouldn't be and that it might be dangerous.
Let's call that sensing danger.
Then the immune system has to trigger
a whole series of mechanisms called innate immunity,
which offer the first line of defence.
In fact, in some invertebrates,
it's the only line of defence.
For them it was sufficient to protect and obviously for their evolution.
In humans, it's sometimes sufficient to protect against the infection.
But the whole idea of the innate immune system is it holds the fort
until the so-called adaptive immune system can react.
Well, if you think about the organisation,
we've got an unpredictable enemy or enemies.
We never know who's going to attack us,
so we need a choice of many weapons that might be appropriate to the enemy.
What's remarkable about the immune system is that generally speaking,
it seems to be able to select the weapons that are best suited to the invader.
Of course, those weapons have got to get access to where the invader is.
That means if they're proteins, they have got to get
there through the circulation and if they're cells,
they've also got to get into the tissues where they might be required.
An important thing about the immune response,
the so called adaptive immune system,
is that once you've encountered your enemy,
you adapt and you expand the weapons based on your past experience.
Which means that you're better able to defend against that enemy next time.
We adapt to the enemy in the adaptive immune system.
In the innate immune system,
we just react in the hope that that will hold the fort.