00:01
We can divide immune responses
into innate responses
and adaptive responses.
00:06
and these have
particular characteristics.
00:08
So, you may be wondering
what the difference is between
the innate
and the adaptive response?
Well, I'm going to tell you.
00:16
Innate immune responses have
a very broad specificity
for what we call
pathogen- associated
molecular patterns.
00:26
deviated to PAMPs,
P-A-M-P.
00:29
Pathogen-associated
molecular patterns.
00:32
This is in contrast to the
adaptive immune response,
which has a very high degree
of specificity
for what we refer to as antigen.
00:41
Antigen is essentially
anything that can be recognized
by the adaptive immune response.
00:47
The innate response lacks a
type of immunological memory
seen in the adaptive response
and often exhibits a similar
intensity upon re-encounter
with the same pathogen.
01:00
However, in some cases,
it may mount an enhanced response
when meeting the pathogen again.
01:07
A phenomenon known as
trained innate immunity.
01:12
We talk about the
primary and secondary
immune response.
01:16
This is due to something referred
to as immunological memory.
01:21
And we will learn a lot more
about immunological memory
later on
in these lecture series.
01:29
And then, finally,
the innate immune response
is a rapid response.
01:35
It occurs within minutes or hours.
01:37
It's very quick.
01:38
The cells already present
in the body tissues,
or are recruited directly and very
quickly from the blood circulation.
01:47
So, you can happen very, very soon.
01:49
In contrast,
the adaptive immune response
is initially rather slow
to get going.
01:55
It takes a few days before
it really gets off the ground
and is fully effective.
02:01
And this is because
the cells need to proliferate.
02:04
They need to expand up in number
in the secondary lymphoid tissues.
02:10
So, on the left hand side here,
you can see that
the innate immune response cells
alive are already in the tissues
at the bottom there on the left,
you can see a tissue macrophage.
02:25
Already sitting in the tissues
lying in wait,
in case an infection comes along.
02:30
And above that, you can see
the multi-lobed neutrophil cell
that is leaving a blood vessel
and entering to go to the place
where the infection is present
in the tissues.
02:45
In contrast,
for the adaptive immune response,
you need cell proliferation to occur
in the secondary lymphoid tissues.
02:54
As we've already heard, this can
take several days to curve fully.
02:59
And then those cells, once they have
proliferated and become activated,
can leave the secondary
lymphoid tissues,
and then themselves
go to the location
where the infection is present.
03:13
So one thing that should already be
coming quite clear to you actually
is that the immune system
needs to detect
that there is a threat.
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It needs to recognize the enemy.
03:25
The immune system is there
to attack harmful pathogens.
03:30
A pathogen,
something that generates pathology,
something that is
going to cause disease.
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So the immune system
needs to be able to detect
these harmful pathogens.
03:43
But there are many things that the
immune system should not respond to
that we don't want it
to respond to.
03:50
It does not attack our
own healthy body components.
03:54
What?
Immunologists refer to as self.
03:59
Also, we've already mentioned
the beneficial
commensal microorganisms,
or microbiota,
as they're often called.
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These also should not be attacked.
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Also, food antigens.
04:13
You probably had
something to eat already today.
04:16
You don't want to attack
the antigens
that are present in
the food and so forth.
04:20
So there are many things that the
immune system should not attack.
04:24
But there are other things
that are harmful,
that the immune system does
need to mount a response against
and eliminate from the body.
04:33
So how does the immune system
actually detect
that there's a threat?
Well, it has a number
of different molecules
that we refer to as receptors.
04:46
And one important
group of receptors
are the pattern
recognition receptors.
04:52
These are sometimes also referred to
as pathogen recognition receptors.
04:56
I'm afraid as you'll see,
there are many alternatives terms
that are used in immunology
for the same thing.
05:03
Pattern recognition receptors,
pathogen recognition receptors.
05:07
They both have BVA to PRR.
05:09
And they both recognize
what are referred to
as Pathogen-associated
molecular patterns or PAMPs.
05:18
That are molecules that are present
either on the surface of pathogens
or sometimes inside pathogens.
05:24
So, pattern recognition receptors
recognize pathogen
associated molecular patterns
in order to determine
that there is a threat
that needs to be responded to.
05:38
And the pattern
recognition receptor
will bind to the pathogen
associated molecular pattern.
05:45
And this will result
in a signal being sent
into the cell of the immune system,
and it will become activated and
begin to mount an immune response.
05:56
As well as recognizing
pathogen associated
molecular patterns or PAMPs.
06:01
Pattern recognition receptors
can also recognize
damage associated
molecular patterns.
06:07
So, maybe you're wondering
what's the difference between
a DAMP and a PAMP?
Well, a DAMP is something that
is produced by our own body.
06:16
These Damage-associated
molecular patterns
are produced by our own cells,
when they become damaged.
06:23
Whereas, Pathogen-associated
molecular patterns
as the name indicates,
are present either on the
surface or within pathogens.
06:34
And just like the pattern
recognition receptors bind to
pathogen associated
molecular patterns,
so, they can bind to the
damage-associated
molecular patterns.
06:48
In contrast, the cells of the
adaptive immune response
have antigen-specific receptors.
06:55
So, in general,
cells the innate response
have these
pattern recognition receptors.
07:01
Whereas, the cells of the
adaptive immune response
have antigen specific receptors.
07:05
In actual fact, is a little
bit more complex than that,
because we now know
that cells of the adaptive response
also have pattern
recognition receptors
as well as the cells
of innate response.
07:16
That the major way
in which cells of the
adaptive-response recognize engine
is using antigen specific receptors.
07:26
And they will bind to the pathogen
using these receptors,
as you can see here.