Title: Innate immunity: The first line of defense How does your
1Innate immunity
- The first line of defense
2How does your body know whats dangerous?
- Your body is constantly exposed to foreign
agents - on the surface of your skin
- when you breathe
- when you eat
- your body comes into contact with many things
that are not made of the same materials as you - Sometimes you come into contact with things that
are dangerous, like influenza virus, or the
salmonella bacteria - A functioning immune system is able to sort out
what is safe and what is dangerous
3Self vs non self
- Your bodys innate immune system is able to
detect things that are dangerous - Things your immune system sees
- Things that are normal and part of your body
self (ex your DNA, your proteins) - Things that are not part of your body non-self
- Not dangerous (ex a carrot that you eat, grass
on your skin, perfume that you breathe in) - Dangerous (ex components of bacteria, viruses,
parasites and fungi)
4The innate immune system
- This is the first line of defense in your immune
system - The innate immune system is a little bit like a
look-out system, it is only alerted when
something different and dangerous comes along
- The goal of the innate immune system is to detect
pathogens and trigger an immune response
5Analogy
- The innate immune system is like a traffic cop
parked on the street waiting to catch people
speeding. The police officer has a detector that
can calculate the speed of passing vehicles.
When someone speeding passes by that, the
detector measures it, and the cop issues a ticket
to the speeder. - Cars passing by at legal speeds are normal, so
the police officer doesnt stop them - these cars are normal, they are like the normal
DNA and proteins in your body - The police officer needs a detector to be able to
determine who is speeding - your innate immune system has pattern recognition
receptors that determine whats dangerous and
whats not) - Cars that are speeding are different and
potentially dangerous, so the cop stops them. - When the cop stops the car, a series of steps are
taken - a ticket is issued
- the drivers information is registered in a
database so that there is a record of the
speeding. - When pattern recognition receptors detect
something dangerous, and a series of steps occurs
inside your cells to try to stop the dangerous
agent from spreading and to warn your body
6Info about innate immune system
- If you did not have an innate immune system, your
body would have no way to detect an infection! - The goal of the innate immune system is to detect
pathogens and alert the adaptive immune system. - Characteristics of the adaptive immune system
- adapts to generate specific immunity, get rid of
the pathogen and remember what that pathogen
looks like if it ever sees it again in the
future. - Characteristics of the innate immune system
- You are born with an innate immune system and it
does not change or adapt as you encounter
pathogens. - The innate immune system has no memory.
- It is not specific to individual pathogens (ex
does not specifically recognize the specific cold
virus you had last winter, but it can recognize
viruses in general) - The innate immune system can recognize patterns
that are the same in many kinds of microbes.
7Detecting patterns
- All the cells in your body have Pattern
Recognition Receptors (PRRs) - These PRRs are responsible for detecting
dangerous foreign agents. How? - Different classes of microbes share certain
characteristics that do not exist in human cells
these are Pathogen Associated Molecular Patterns
(PAMPs) - Example human cells have nucleic acids that are
normal (DNA, mRNA, tRNA). Bacteria and viruses
often have different nucleic acids.
8The pattern recognition receptors in your cells
can tell which nucleic acids are dangerous and
which are normal.
9There are PRRs in your cell membranes and inside
the cytoplasm of your cells. Scientists have
identified around 15 different PRRs in humans,
each of which is specific for a different
pathogen associated molecular pattern. That way,
viruses, bacteria, parasites and fungi can be
detected by the innate immune system.
10- When a microbe infects a cell, the PRRs can
detect a PAMP from that microbe - This recognition activates a cascade of events
involving cellular proteins. - At the end of this cascade, a protein is sent to
the nucleus which signals the DNA to make
proteins that start an immune response - These proteins can
- Create an anti-infection state in the infected
cell so as to slow the grow of the microbe - Warn surrounding cells that there is an invader
nearby - Recruit cells from the immune system to come help
clear the infection - Help activate immune cells that are specific for
that particular microbe
Click once for the animation
11Where is the innate immune system?
- All your cells have PRRs, because all your cells
are susceptible to infection! - Some cells have more types of PRRs and can
respond quicker (ex dendritic cells)
12- When a virus infects a cell, a PRR detects it,
triggering a cascade of signals. - Immune proteins are made
- Some of these proteins are secreted and can warn
surrounding cells that theres an infection
nearby. Some proteins can recruit other immune
cells to the site of infection.
- The infected cell can break down viral proteins
and show them to the newly recruited immune cell
(a T cell)
- The T cell is now activated and can recognize the
specific piece of protein from that specific
virus. Because of the signals from the innate
immune response, the adaptive immune system can
now generate a specific response against the
virus, can clear the virus and remember that
specific virus so it cant infect you again in
the future.
Click once for the animation
13You need both!
- In order for the human immune system to work you
need - An innate immune system
- An adaptive immune system
- Without either of these, your immune system would
not work
14Other species
- Most multicellular organisms have an innate
immune system - Other mammals have both innate and adaptive
immune systems - Butinsects and plants only have an innate immune
system! - Did you know
- Pattern recognition receptors were first
discovered in fruit flies - Sea urchins have over 200 different types of PRRs
to defend themselves
http//www.news.wisc.edu/newsphotos/images/fruit_f
ly_research03_6801.JPG,
http//www.alaskaunderseatours.com/photos/Red-Sea-
Urchin.jpg
15Conclusions
- The innate immune system is the first line of
defense against pathogens - Your cells have Pattern Recognition Receptors
that can detect elements that are conserved in
many kinds of microbes Pathogen Associated
Molecular Patterns - Recognition of something dangerous leads to a
signal that warns other cells and the immune
system that there is an invader - Without the innate immune system, your body could
not fight off infection!
16Extra information
- Pathogens are often able to trick the innate
immune response
17- Many microbes are able to block the innate immune
response. - Some are able to block this cascade of events at
various stages - Examples
- Influenza virus has a protein that is able to
hide its RNA so that PRRs cant detect it. - Hepatitis C virus is able to break apart a
protein involved in the innate immune cascade - Mycobacterium tuberculosis can prevent gene
transcription
18If a microbe blocks the innate immune response,
what happens?
- Case 1 Immune system wins.
- Microbes arent usually able to fully block the
innate immune response. Therefore, a immune
response is generated and the pathogen is
cleared. - Ex Influenza virus. The virus cant block the
whole innate immune response, and the infection
is resolved. - Case 2 Pathogen wins.
- In some chronic infections the immune system is
never fully able to clear the pathogen. - Ex Hepatitis C virus. Microbes that cause
chronic infections are able to block the innate
immune response at many stages, and have methods
to deter the adaptive immune response as well.
Hepatitis C is a lifelong illness with no cure.
The current treatment involves stimulating the
innate immune system.
19Made possible by
www.immunologymontreal.ca
www.cihr-irsc.gc.ca/synapse
www.mcgill.ca/hostres/training