Immunology – Immune Response Towards Bacterial and Viral Infections Page 1
Dr. Stan G. Louie
October 5thth, 2009
Immunology
Notes by Tony Dao
Immune Response Towards Bacterial and Viral Infections
Objectives
These are today’s objectives. We will talk about how the immune
system is activated and also how to prevent it and how to respond to
it. Don’t think that the immune response working is always good. If
you get overreaction you can die from septic shock. This is why when
you talk about this, you want an orchestrated response that is
accurate. One of the misconceptions is that if you have cells, it’ll
work. Just because you have the cells, it doesn’t mean it works. You
have to make sure the cells work properly. For example, in leukemia,
you have a lot of white cells but they don’t work well. People who die
from leukemia die from infections because the immune response is
not working properly.
Diagram
If you remember correctly, the best immune system is
your barrier system (your skin). If you pick open a scab,
you will have infection. There are some of you who have
a mucosal layer that’s thick. If it’s thick, is it good or bad?
Depends. If it’s too thick, it can gag you to death. If you
have enough, it will be able to cough up bacterial stuff.
When we turn on a heater, it dries up our mucosal
membrane so the layer gets thinner and thinner, but the
constituency is thicker so it can transported through the
skin for infection. So this is why you need a mucosal
barrier.
Also, the mucosal barrier is continually exchanged. Why is that? Well, if you don’t poop every day, it’s not good. So the
bacteria will stay. This is why these people are at higher risk of getting colon cancer.
Also, it depends on what you eat. If you have a carb diet you won’t move along that
much.
Just because the fluid goes out one way, it can’t go out the other way. It does, it has an
osmotic pressure. It’s very important that you have an intact mucosal membrane.
Diagram
You see that these are all lined with mucosal membrane continuously sloughing off. It
becomes a protectant layer and becomes part of your fecal matter that you excrete.
Immunology – Immune Response Towards Bacterial and Viral Infections Page 2
Diagram
Sometimes we forget we have lymph nodes in our oral cavity. Remember back
then when the people wanted to remove tonsils? That’s not a good idea. They
would also give tetracycline, but that has side effects. It changes your floura and
you don’t know the long term toxicity. Remember, we used to think the penicillin
was good, but long term causes hepatic toxicity.
So sometimes when you get strep throat, you get swollen lymph nodes. The
lymph nodes are swollen because they’re trying to fight an infection. Too much
could be catastrophic. The tonsils are inside there. Sometimes your tongue gets
thicker as well. Thick is usually a hypersensitivity reaction. Why is your tongue so
thick? It prevents your allergens from coming in, but it can constrict your
bronchioles and you can’t breathe and die. If you get swollen tongue or face
swelling, you need to go to the ER right away.
Diagram
The mucosal membrane sloughs. Note in the crypts here are intestinal stem
cells. They grow up to be the microvilli of the GI. Why is it there? The
lymphatic tissue runs along to the microvilli. It would come off, so if anything
are toxic it would protect your GI. The other reason is there’s protection of
lymphatics. The peyer’s patch is lymphatic later down the GI. Remember
when you have chemotherapy you don’t eat fresh fruits or vegetables
because of the bacteria. If you ate an apple and you’re on chemo or
neutropenic, then you’d get a bacteria infection. What about strawberries?
Strawberries are grown in fertilizer. Fertilizer is poop, and the reason we had
the hepatitis before is because it was human waste in the fertilizer. Peyer’s
patches are immune cells that secrete antibodies that kill bacteria.
Picture
This is a dome of a Peyer’s patch. Notice here a lot of T cells, and a germinal
center. You have a very good immune system so you can eat a lot of junk. How
many of you eat old pizza, or even cheese? Bread has yeast. These things can all
cause problems if you have a weak immune system.
Picture
This shows M cells. The macrophages
and dendritic cells go through to
suppress bacteria from going into the gut.
Immunology – Immune Response Towards Bacterial and Viral Infections Page 3
Diagram
M cells facilitates dendritic cells to go up. The bacteria cells
will get eaten up if they try to go through. The idea is to keep
the bacteria level as low as you can. So is there bacteria in
your blood right at this moment? Absolutely. You don’t have
clinical syndromes because your immune system is fighting it.
Know the difference between symptoms and clinical
syndromes.
Picture
This shows the M cell protecting the gut. Everyone has to get a colonscopy at age 50. This is
to detect if you have colon cancer. If anyone in your family has colon cancer, we do it at
age 40. This is something you want to think about.
Diagram
This is showing the dendritic cell
reaching up and grabbing the
bacteria. The HIV would use this to
affect. Look at the micrograph; this
shows like a hand reaching out and
grabbing. There are a lot of
pseudopods on these dendritic cells.
Diagram
What happens when the bacteria gets in? Once it gets in the
intestinal cell, it induces a change in the conformation of the
endothelial cells. Remember the endothelial cells can induce
expression of adhesion molecules. So, once the NK cells get close by,
it will eradicate the bacteria. This is how the endothelial cells tell the
immune system that it is being infected. Why is this important? This
is how you prevent systemic
infection!
Diagram
If there’s a bacteria that gets in the system, crypt heart mesenteric.
Inside the gut, you’ll see nodule-like stuff in the intestine. These are your mesenteric
nodes, and they are in your small intestine that prevent infection. They are like filter
blocks, and it also has lymphocytes that will kill the bacteria. So when you have
lymph node enlargement, you know there’s an infection and bacteria is sequestered
there.
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Notice here there’s a lot of activity. The Peyer’s patch are higher up, and they are the first line of defense. If bacteria
gets through the peyer and mesenteric, then it becomes a systemic infection. If you have activation of the mesenteric
nodes or the lymphatic nodes, you get cytokine activation. Cytokines are soluble growth factors and sends systemic
signals. It will recruit more cells to the site, and you will have more adhesion molecules so the cells being recruited will
know where to go.
Detection of Antigen
There are several ways of detecting antigen. We talked about IgM
nonspecific and IgE specific. The IgE would come 3-5 days after the IgM.
The complement factors then come. We assume the nonspecific are
already localized. If there is endothelial damage, there is release of IL-1.
The α IL-1 is intracellular, the β form is the one that circulates all
around. The IL-1 then increases expression of IL-8, aka neutrophilic
chemotactic factor. This turns on neutrophils, and causes localization of
neutrophils and macrophages. These are key elements to tell infections
where to localize and how to neutralize the effects.
Types of Antigens Will Determine The Type of Immune Response
If this is the first time you see an antigen, it takes time. Once the
antigen is seen, it has to be broken down by the macrophage and
present it to the T cells that activate a set of systems that cause IgG
formation. Then you get memory cells, so these will have pre-formed
antibodies of IgG (more specific). Why is IgG more specific? It has the 3
amino acids and it also has the FC region that can recruit immune cells.
These will be able to know where to localize. The Primed T cells have
primed TCR.
If you have a viral vaccine and bacterial vaccine, which one is longer
acting? It’s the virus vaccine. Why is this? The lymphocytes are in
charge of viruses, but more importantly lymphocytes are longer living
than neutrophils. Lymphocytes can have a 30 year lifespan, but then you don’t really know the answer. This is why a
viral vaccine may be life long. The bacterial vaccine you probably have to give it every year. How do we know this? The
pneumococcal vaccine has to be given every year.
Diagram
Here, there’s inflammation stimulation and rolling. We
showed you this a lot so it’s important. Then there’s
activated integrin, firm adhesion, and transepithelial
migration. Why do you have to have the cells go from
vascular to extravascular? Because that’s where the
pathogens are. The cells can clear the pathogen (total
clearance) as opposed to only neutralization by antibiotics.
Two pt, one gets steroids, one gets antibiotics. White blood
count goes up. Which is better? The steroid pt goes from 5 to
Immunology – Immune Response Towards Bacterial and Viral Infections Page 5
11 thousand in numbers of the white blood cells. Where is it coming from? It’s coming from the blood vasculature. You
have cells already on the wall of the vasculature. They are holding on. When you are giving steroids, what happens is it
decreases the adhesion molecules, so all the white blood cells drop off from the walls. However, steroids reduce
immunity, so just because you have more white blood cells doesn’t mean you have better immunity. If you get steroids,
B cells are of no value. The cells you get are not functional white cells.
Why would you give steroids? Remember patients who can’t breathe. The steroid would reduce the inflammation by
lowering the adhesion molecules and reducing the immunity. So note that steroid pt are susceptible to pneumonia. So
notice that steroid pt have high white blood cell count. If you know the pt can be infected, then give them antibiotics,
too.
Immune Response to Antigens
This is your bacteria and macrophage. There’s
antigen presentation with MHCII, turns on T cells or
B cells. Same old slide we’ve seen over and over.
This is a very important paradigm, we need to
memorize.
Functions of Blood cells (important)
You have all these blood cells in your body. The first thing you see when you puncture your finger is red blood cell. The
red blood cells are for oxygen and CO2 transport. The platelets
are important for platelet aggregation.
White blood cells have several types.
Granulocytes have neutrophils. These are defense against
bacteria and fungal infection. If you have a depletion of
neutrophils (cycloneutropenia, goes up and down), they die
from inability to fight off bacteria infections. The eosinophils
are important for host defense against parasites and allergic
reaction. Dysentery, amoebas, tape worms, etc. are the
parasitic ones. They are also important in allergic reactions,
such as hay fever. The eosinophilia is high if you have hay
fever.
Example of questions: Increase in neutrophils (usually at picnics with a lot of mayonnaise) is usually from bacterial
infection. No increase (with traveler’s diarrhea) could be parasitic. Caesar salad you get raw eggs, hollandaise sauce.
Basophils we don’t know what they do. We know it’s involved in inflammation and allergies. We think mast cells belong
to eosinphils (will not quiz us on this).
Macrophages are dendritic cells (gut), monocytes, Langerhans cells (tissues, skin), astrocytes/microglia (brain), and
Kuffer cells (liver). These are involved in antigen presentation, immune regulation, and tumor lysis.
B cells are involved in antibody production. What kind of infections are you susceptible to if you don’t have B cells?
Remember these make antibodies. If you don’t have antibodies, you can’t bind to encapsulated bacteria. So pt with B
Immunology – Immune Response Towards Bacterial and Viral Infections Page 6
cell elimination will be susceptible to encapsulated bacteria infection. Babies don’t have many B cells, so they are also
susceptible to the same thing. This is why I want you to learn this; these are the pt you see.
T cells are very important for viral and fungal infections! The T cells are critical. You can probably see 1 or 2 questions
coming from this slide alone.
Hematopoietic Paradigm
All the cells in your body come from the pluripotent
stem cell (-many cells). This comes from the bone
marrow. We first thought it was just for your blood
cells. I can tell from the cytokines what cells come
from what. Note the myeloid cells on the left. These
are good for bacteria and fungus, and some
parasites. The lymphoids, particularly T cells, are
virus and fungus. Red blood cells are for oxygen
transport, repair, and clot formation. Eosinophils we
know for sure are for allergic reactions and
histamine release.
How does the cell know to make a myeloid or T
lymphocyte?
Inflammation: Neutrophils vs. Monocytes
This sort of gives you what is what. Monocytes/macrophages
are what we call cytokine producing. The two important ones
are monocytes and naïve T cells (aka helper T cells). Know all
the macrophages.
Neutrophil Phagocytosis of Streptococci sp.
What is this? This is a picture of neutrophil phagocytosis of streptococci.
This is a macrophage eating it up. What is the stuff around there? It’s
granule release.
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Phagocytosis and degranulation
So you have the granules and phagocytosis. Why are granules
in little pockets? So they won’t destroy the cell. What’s inside
the granules? Lysozymes are inside the granules that break
stuff down, lyse the bacteria. The degranulation leads to the
phagolysosomem to kill the bacteria.
Types of Neutrophilic Granules
What kind of granules are they? The key ones are myeloperoxidase.
What is myeloperoxidase? It’s a peroxidase that forms peroxide. Dr.
Shen probably already talked to us about lactoferrin. These are
important; they are iron containing regiments that kill bacteria. If
you get burned, you will get a drop in the level of lactoferrin and
you can die because of this. Iron in itself is also an antiseptic.
Why do you have gelatinase in granules? This gelatin is a rat tail
collagen. One thing is it degrades the capsule. The other thing is
that it breaks down the basement membrane.
Neutrophil Granules
You don’t need to memorize everything.
Notice here the monoperoxidase are microbicidal proteins. The
gelatinase and collagenase are there to gain access to the
infection. If you get a mosquito bite, there’s histamine release.
Lactoferrin and B2-microglobulin are very important. The B2
microglobulin is an activator of the interfeuron.
Progression of phagocytosis
The oxygen forms peroxide that kills. This is critical.
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Major oxidative microbicidal pathways in neutrophils
How does oxygen get converted into peroxide? This has O2 form
to superoxide, then it forms peroxide. The monoperoxidase
converts peroxide to perchloric, which is bleach. The bleach is
the best antiseptic you will ever have. Bakin’s solution is a
teaspoon of bleach and a lot of water, and this is best for fungal
infection. Take half a teaspoon of bleach in warm water and soak
feet in 5 minutes, then you shower.
Nitrite is toxic and kills locally.
[Missed what he said at 4:09 PM]
Effect of S nitrosopenicilllamine on cutaneous
leishmania ulcers
These lesions usually go away. This shows that if you
gave nitric oxide donors, you can kill bacteria and
parasites. What I’m trying to do is get you to use basic
understanding of this to change the world. This is an
epidemic disease outside of the United States.
Biological Effect of Nitric Oxide
If there’s too much NO, there’s vasodilation. Now Viagra is
used in ocular hypertension for women. They usually see blue
in their eyes, but now they will see normally because the
Viagra would inhibit PDE in the eye. Now we’re developing ear
drops to cause dilation to cause drainage of the ears. Ear
aches is number 1 cause of meningitis in kids.
NO is also used as a neurotransmitter. It inhibits aggregation
of platelets. If you have too much NO, what would happen?
There will be a drop in blood pressure. Remember, you make
NO in your body. If you make too much, you get hypotension.
If you have it long enough, you faint and don’t get enough
oxygen.
Biological activity of nitric oxide
Here’s how it works. You got arginine, and there’s two type of nitric oxide
stuff. There’s NOS (nitric oxide synthase). The iNOS stands for “inducible”.
When you feel faint after an infection, that’s because the cytokines in your
body activated this to cause more NO. You basically vasodilate.
If you go too far, there’s septic shock. This is because there’s too much NO.
You vasodilate too much and your body will increase your heart rate.
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Stuff written in class:
Equation: BP = CO x TPR (aka SVR, systemic vascular resistance)
This is also = (SV x HR) x TPR
If you have NO, the TPR will go down. Therefore the BP goes down. What’s the first thing you notice? You will get light
headedness. If you get that, before you faint, your body will want to compensate. Therefore, your HR will go up. You are
trying to compensate for the lowering of the TPR because of the increase in the NO. How hard can your heart pump
before you die? 140 bpm because once this happens your blood will swash back and forth, and you have blood stasis
and you will clot and you will die. If you have septic shock when you’re sick, what is the first thing we tell you to do? We
say you need to drink a lot of fluids because you need to increase your stroke volume. When you are sick, you evaporate
so that’s why you need to increase the water intake. Don’t use caffeine because SV will be lower even though it increase
HR. Remember epinephrine and dopamine is similar as well. This is basically teaching you how to handle septic shock.
Hematopoietic compartments
What happens in the bone marrow is… you have
increase of all the cells. This essentially shows you that
the myeloblast forms neutrophils and macrophages.
These are key; when you have a bacterial infection,
you need to increase this part.
Cytokines and chemokines affecting
granulopoeisis and monopoiesis
You would increase the cells by increasing the
cytokines. The GM-CSF (colloid stimulating
factor) is important. The G-CSF on bottom
should be called N-CSF because it’s for the
neutrophils. This is used to reduce bacterial
infections as well as recovery after
chemotherapy. In a bacterial infection, you will
see increase of G-CSF and GM-CSF because it’s
a response to bacterial infection.
Effect of G-CSF on Neutrophil Production (Slide won’t reproduce on PDF)
Note the left side is normal. This looks quite long. If you see an infection or G-CSF stimulated side, the mitotic is faster
because the body needs to make more cells to fight off the bacteria.
Immunology – Immune Response Towards Bacterial and Viral Infections Page
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Endogenous cytokine levels in febrile and afebrile
patients
Afebrile means they don’t have fever. Febrile
means fever. Note the control is low in cytokine.
The afebrile neutropenia has low G-CSF and GM-
CSF. The nonneutropenic bactermia pt has elevated
G-CSF, but not GM-CSF. The febrile neutropenia has
a skyrocket in G-CSF, which shows how important it
is in bacterial infection fighting. Note M-CSF and IL-
6 also skyrocket, which shows their importance as
well.
Effect of pathogen type on cytokine levels
Let’s look at the levels of the cytokines in different
pathogens. This is a box and whisker plot. Note here gram
negative has a substantial increase, an there’s a huge
increase of cytokine for G CSF. The GM-CSF hardly even
moves, so it’s not that important in response to pathogens.
IL-6 only increases in gram-negative and fungal. Gram
negative has LPS, and gram positive has exotoxins.
So basically, the two major effects are on G-CSF and M-CSF.
Anyone who has elevated IL6, we usually tell you have a less
than 5% chance of living.
This data is not new data, it’s pretty well established.
Endogenous G-CSF levels in febrile and afebrile patients
Notice that only when you have bacterial infections that
you see an increase in G-CSF. Predominantly, the
infections are gram negative infections. Take home
message: 2. If you have low G-CSF levels, there’s alow
cha [4:31]
How do you treat a pt with cycloneutropenia that have
no G-CSF levels? Give them G-CSF (Neutrogin?). This is
supplementation.