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Lecture

Notes taken during lecture


Department
Immunology
Course Code
IMM250H1
Professor
Dana Philpott

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LECTURE January 25
Last weeks class
Commensal flora, mechanical forces, etc. maintain mucusoal surfaces clear of
infection
BARRIERS extremely efficient
Innate and adaptive come into play only when these barriers fail
Two organisms capable of entering bodies, bypassing the barrier
Innate immunity
AKA inborn
Use innate system to defend self against infection
In these lower organisms, innate immunity the only system for protection
Innate immunity
Present in all mutlicellular organisms
VERSUS adaptive system - relatively recent in evolutionary time
oUnique to vertebrate animals
Set number of recognition molecules encoded in genetic material
cannot be modified receptors have evolved to detect patterns of microbes
that do not change in the huge diversity of microbes
VERSUS adaptive system adaptive immune system infinite number of
recognition molecules
immediatley active cells VERSUS adaptive system cells need the
innate system to prime these cells in order to attack
No memory VERSUS adaptive system, memory of infection see an
organism once, see it a second time, body extremely efficient quick to get
rid of the infection
Competent immune system yellow line
The normal response most individuals have to an infection
Infection first controlled by innate system BUT lacking adaptive system –do not clear from
body
Organisms win
Likely will grow to adulthood
Absence of innate immunity most serious consequences
Infections cannot be controlled at all
These people die early in childhood likely
Really, both systems required
Discovery of the innate immune system
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- M looked at invertebrates (ie. starfish) how they react to different insults
- he cauterized the surface of starfish larva
- phagocytes seen going to point of injury engulfing the injury
- raised question about how cells tell something is foreign
Step on splinter body reacting to the microbes on the wood these are
foreign so the body reacts to these foreign microbes
VERSUS
Body reacting to dead or dying cells telling body something is wrong,
come to clear this injury away
Lots of debate
BOTH ARE ACTUALLY CORRECT recently determined
MAMPS and DAMPs signal immune system
Overview of innate immune response
MAMP and DAMP are both danger signals that the body receive
Recognized by pattern recognition molecules
Once reaction takes place, signal transduction occurs allows for change
in cell leading to destruction of microbe barring anything going wrong
ALSO, called PAMPs but not specific to pathogens so prefer MAMPs
These MAMPs represent structural components of microorganism that
cannot be modified, otherwise will wreak the structure of the
microorganism
Bacteria
Stain used to differentiate bacteria into 2 groups
Basis based on cell wall of these bacteria
Have different sensitivity to antibodies
oThe Gram stain
Put culture on microbe slide, pass over heat, thus fixing microbe
onto microscope slide
Stain with crystal violet purplish blue coloured
Treat with iodine fixes the stain into the cell wall
Treat with ethanol to decolourize
In gram negative purpleish blue colour washed away
Counter with safarin gram positive retain the purple blue colour,
so do not pick up counter stain
oBASIS for stain is the different cell wall
Gram positive cell walls
Cell wall structure made of peptidoglycan molecules
crosslinked with lipoteichoic acid and wall teichoic acid
oMeshwork outside gram+ cell wall
oMaintains structure of organism
oIf poke holes in bacteria cannot survive because
cannot maintain structure
oMore efficient?
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Gram negative cell walls
Inner membrane AND outer membrane 2 membranes
Between membranes have peptidoglycan unlike outside of
cell wall like in gram + bacteria
Lipopolysaccharide specific to gram negative bacteria
Bodies react v. strongly against these lipopolysacchardies
Gram positive retain because the peptioglycan hold onto the first
stain
Versus gram negative = cannot hold onto the stain, so it washes
out
Endotoxin = LPS
Peptidoglycan - found in both + and
Are MAMPs that our bodies can use to start an immune response
These are things our bodies recognize
Also extensions flagella enable bacteria to move
Immune system can recognize flagella, the base unite flagelin
These are protein-based
MAMPs also include genetic material of bacteria dn viruses
Some specificity in immune sytem
oDNA immune system reacts to CpG sequences mostly in bacteria
Very few such sequences in our own DNA
If they occur, they are methylated to conceal from our
immune system
Most likely signature of microbial infection
oRNA often associated with viruses
oTHESE ARE NUCLEIC ACIDS and our bodies can respond against
these
Fungus can be recognized by immune system we have evolved to recognize all
sorts of things
Zymosan carbohydrate released from cell wall of yeast
Also recogtnize beta-glucan -
THEse are carbohydrate structures
Now, on to DMAPs….
Include high intracellular levels of reactive oxygen spec ies (ROS)
Normal product produced by phyagocytic cells
Danger signal when produced in such high quantities
2. Release of potassium
oHigh concentrations inside cell
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