immuno - lec 20

7/31/2019 Immuno - Lec 20

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Inflammation

Dua'a Herzallah

Ziad Al-Nasser

Sunday, 31/7/2011

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7/31/2019 Immuno - Lec 20


Immunology- Lecture #20

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Peace up colleagues Ramadan Karim! I tried to make this lecture as easy as I could!

Study it thoroughly, & remember that nothing we learn in this world is ever wasted.

A very BEAUTIFUL saying of the prophet (PBUH) to start with:

"Acquire knowledge. It enables its possessor to distinguish right from wrong; it

lights the way to heaven; it is our friend in the desert, our society in solitude, our

companion when friendless".

The professor completed chapter 21, finished chapter 22, and started with 23, so

let’s get going:

We will continue with the innate immune system, we talked about macrophages and

natural killer cells, and how do they play a role in defense.

Natural killer cells use the same mechanisms of the cytotoxic T cells, they have

small granules in their cytoplasm contain proteins such as perforin and proteases known

as granzymes, but NK cells are non-specific. The role of NK cells start when there is

suppression or there is no presence of the MHC antigens. NK cells have two receptors

that sense the presence/absence of the MHC antigens, so the one the we call KIR

(Killer-cell immunoglobulin-like receptors) and the CD94 (or NKG2), if the MHC

antigen is present it will give a negative signal and won’t be activated and vice versa.

The activation of the NK cells is through a mechanism called Antibody-dependent

cellular cytotoxicity (ADCC). NK cells express the Fc receptor (FcR) molecule whichis an activating biochemical receptor that binds the Fc portion of antibodies. When

antigen binds to an antibody, this antibody will bind to the NK cell through its receptor,

if this happens and MHC was there, then the NK cell will be activated, pores will

develop in the cytoplasmic membrane, granzymes will enter inside and induce the

process of apoptosis.

We talked about Apoptosis and its importance in many aspects in the body.

We also said that in our body we have anti-apoptotic pathways in order to keepthese cells alive for a longer period of time like the BCL-2 gene, that interferes with the

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function of the cascades enzymes and no destruction to the DNA is going to take place.

And sometimes we need these cells to stay in our body for a longer period of time, like

memory cells for example. You should know what triggers the activation of BCL-2

mechanisms; one of them is the production of IL-2 which is very important in cell

development. It has to be produced for a while then it has to stop otherwise the reactionwill keep going on for a longer period of time.

Binding of IL-2 to its receptor is going to activate the cell to express more of the BCL-2

to keep the cell alive for a longer period of time. Any problem related to the expression

of BCL-2 anti apoptotic pathways keep the lymphocytes proliferating abnormally

which will lead to lymphoma.

Do you know that BCL-2 has been implicated in many cancers and diseases

such as schizophrenia, as wiki says: Apoptosis plays a very important role in

regulating a variety of diseases that have enormous social impacts. For

example, schizophrenia is a neurodegenerative disease that may result from an

abnormal ratio of pro- and anti-apoptotic factors. There is some evidence that

this defective apoptosis may result from abnormal expression of Bcl-2 and

increased expression of caspase-3.

We talked about parasites; they have to be destroyed by mast cells in an acute type of

inflammation. Some parasites like schistosoma are so evasive that they cover

themselves with body antigens, red blood cells, & MHC antigens so the body will

recognize them as self so they stay in the body without even noticing them. Theproblem comes when the female of the schistosomal couple lays down so many eggs,

so these eggs will be washed back to the liver through the venous blood where a

chronic inflammatory process takes place.

So in parasitic infections, you could end up with a chronic inflammation that is going to

induce lots of interferon gamma & TNF that will lead to liver damage and failure.

Sometimes these eggs lodge in the urinary bladder or in the bowl and while trying to

get out into the lumen they get trapped there and induce severe inflammatory type of

reaction. So eosinophils play a major role in that and we talked about the molecules

that we have inside, the cationic proteins, peroxidases, and beside all of the vasoactive

amines. They play a major role in that. I want you to remember that sometimes the

killing process and the presence of hyperesoniphelia could induce a chronic

inflammation and we could die as a sequel of that chronic inflammation.

Finally he finished, and I am sure this is the 15th

time he repeats what he said on the

same subject, so study it from the previous lectures.

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Chapter 22:

So this will bring us into the process of inflammation

Inflammation is a non specific immune response that will call upon inflammatory cells

to come into the area, any tissue damage in our body will induce the process of

inflammation. These inflammatory cells we are talking about are mainly neutrophils &

macrophages. Macrophages will be stimulated first because they are in the tissue and

then chemotaxis will bring the neutrophils into the area, the products of the granules of

the inflammatory cells in general will activate macrophages and seal the area to clear

the infectious process.

We have two types of inflammation: Acute & Chronic inflammations.

1- Acute inflammation:

(I gathered all of what the professor mentioned about it throughout the lecture)

Acute inflammation is an innate response mediated by neutrophils, or mast cells. So

when we have an infection or injury to the tissue, we start with the acute inflammation

process, it is an innate response mediated by neutrophils mainly, complements, &

interferons and this is going to activate the adaptive immune response.

So if the acute response manages to clear the infection we’ll stop here, but if it couldn’t

then we’ll go to the chronic inflammation which has a different mechanism. In the

acute inflammation we see pus, if it is yellow then it indicates the granules in the

neutrophils.

In influenza for example, it is well known that it doesn’t cause chronic type of

infection, 10 days maximum and the virus is cleared, nobody stays infected for a longer

period of time.

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And when I talk about the process of inflammation I talk about hotness, redness, edema

(because of the vasoactive amines) and tenderness (painful and itchy area).

And here is what I want you to know concerning the acute response in the viral,

bacterial or worms infection. Each has a different mechanism and different moleculesand cells responsible for the acute response. The professor only read the figure below

because it is more than clear.

Acute viral infection here to start with, if it manages to clear the viruses, if it fails

change to chronic and chronic type of inflammation leads to tissue damage.

2- Chronic Inflammation:

It is mediated by macrophages and the formation of granuloma and the delayed typehypersensitivity and the hypereosinophilia that we have talked about before. In chronic

inflammation we have activation of macrophages, granuloma or what we call delayed

type hypersensitivity reaction (DHR and granuloma are synonyms of the same thing.)

While in the chronic inflammation we don’t see pus, we see thickening (granuloma) or

the PPD (we’ll talk about it).

Examples on the chronic inflammation that I want you to remember:

Tuberculosis in the lungs, Hepatitis B in the liver when we get acute hepatitis and jaundice, around 10-20% of these cases could develop into chronic Hepatitis B that

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leads to liver damage, and the Schistosomiasis that I have talked about in the

entrapment of eggs in the liver, urinary bladder or the GIT.

The signs and symptoms of the inflammation: hotness redness, edema tenderness,

swelling, pain, white blood cells, & tissue infiltration. Remember that neutrophils are

not present in tissues; they are called upon so the stimulation starts with the

macrophages.

We have the physical stimulation, & the immunological stimulation (TNF which comes

mainly from macrophages and it causes necrosis to tumors in animals but it raises our

body temperature and plays a major role in apoptosis.) If stimuli could not be removed

by the acute process, then it changes into the chronic. And macrophages will take

release here.

So we start with pyogenic (pus forming) infection in the acute, ends up with activated

macrophages and granuloma.

Acute viral infection here to start with, if it manages to clear the viruses, if it fails

change to chronic and chronic type of inflammation leads to tissue damage.

Edema comes from mast cells and we talked about that and the diapedesis of the plasma

into the area and the eosinophils and how can they damage the parasite and the

vasoactive amines in these eosinophils also induce tissue damage. I want you to

remember that the ultimate goal of these inflammatory cells is to get rid of the invading

microorganisms but sometimes if they fail, if you have immunocomplexes and thesecomplexes are adherent to the basement membrane of the kidneys, so the macrophage

will come and try to phagocytose the immunecomplexes but they can’t because they are

so stuck to the B.M of the kidney, so they release their vasoactive amines mediators to

the basement membrane and this causes damage to the kidney. so this is an outcome, it

was not designed to damage our tissues but the process lead to that.

In chronic bronchitis in smokers, why do they cough? Because macrophages come to

the area trying to clear the carbon molecules in the respiratory tract, and they fail!! So

they release their hydrolytic enzymes and cause damage to the mucosal lining of the

respiratory tract because of the stimulation of mucous secreting glands and so on.

So remember the term Delayed-type hypersensitivity reaction, here we are talking

about TH1 cells and macrophages. And we know that we have (DTH) by performing

skin tests, like the PPD skin testing & lepromin testing.

Here the doctor READ the following table:

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So when we talk about inflammation, we are talking about a network of cytokines that

induces all of these changes that occur in our body. In acute inflammation we have a

cytokine network, it is supposed to clear the infection and if it fails it changes into a

chronic inflammation. So the cytokines that are involved:

IL-1, and IL-1 is present within macrophages and many other cells as well, suchas ) and it is needed to activate the macrophages & T helper cells.

TNF (tumor necrosis factor), remember it is involved in fat metabolism, fever &

apoptosis.

GM-CSF, which recruit more neutrophils and monocytes into the area of

infection.

IL-12 to which will stimulate the differentiation of T helper into TH1.

IL-18, it is almost the same as that of IL-12.

Remember that NK cells produce Interferon gamma ( it is secreted by Th1 cells, Tccells and NK cells) which is important in MHC Ag expression, Ag processing,

Macrophage activation, NK cell activity, TH2 suppression, and has an antiviral effect.

IFN-γ is the primary cytokine which defines Th1 cells: Th1 cells secrete IFNg, which in

turn causes more undifferentiated CD4 cells (Th0 cells) to differentiate into Th1 cells,

representing a positive feedback loop - while suppressing Th2 cell differentiation.

Always we have a balance, when TH1 is activated then TH2 is suppressed and vice

versa.

So, here we talk about cytokines network, here macrophages will be activated first,

production of IL-12 which will stimulate the differentiation of T helper into TH1, here

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in this case for example interferon gamma and how interferon gamma will act on the

NK cells and NK cells can produce interferon gamma which will act on cytotoxic T

cells which to perform the killing and the activation of macrophages and formation of

granuloma.( please refer to the figure below to understand the idea more thoroughly).

Tuberculosis is a classical example of chronic inflammation and the development of granuloma (what we call delayed - type hypersensitivity reaction), we are talking about

lymphocytes of TH1 and activated macrophages. Tuberculosis is a reemerging

infectious disease, nowadays because of using immunosuppressive drugs, radiotherapy

& cytotoxic drugs; we can see the M. tuberculosis is on the return again, so we have to

be aware that patients might be getting this infection. Simply, here what we are getting

in this chronic inflammation is activated macrophages and this will occur through the

toll-like receptors like TLR-2 & TLR-4 for example, and the warning signals that will

come out of the macrophages, IL-1, IL- 12, IL-6, IL-8 & TNF all of these come from

macrophages.

In M. tuberculosis, the bacteria structurally have mycolic acid, waxes and so on that

they can stay in our body in a longer period of time and stimulate the delayed-type

hypersensitivity response, so it changes into a chronic inflammation with granuloma

and activated macrophages, epitheliod & giant cells that will kill the mycobacterium

tuberculosis.

We call the infection when we are firstly infected the primary infection, and usually it

occurs in the lungs so alveolar macrophages are going to phagocytose those bacteria

and they resist killing here.

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If we are already vaccinated with the BCG vaccine or exposed to antigens of M.

tuberculosis then things will be different, we will have more of the activated

macrophages that will clear the site of infection. So when the macrophages are

activated through the cytokines network that we have mentioned, macrophages will

come into the area, activated macrophages will change into epitheliod cells and multi-nucleated giant cells. TNF will be produced, necrosis in the center of the lesion will be

found and it is a cheesy necrosis we call it casiation necrosis.

Tuberculosis outcomes:

1- If the granuloma was near a bronchus for example,and we had excessive production

of TNF, then it will open into the air and the microbes would have access into the

environment, we call this open TB.

2- The bacteria could be taken with these macrophages through the circulation into

anywhere of the body, we call this military TB or tuberculosis meningitis if it

reached the CNS. Widespread primary TB occurs in a small proportion of young

patients, with dissemination all over the body.

And wherever bacteria go to the body, to the brain, kidney or bone, granuloma will be

formed and this will damage the tissue that granuloma is landing on!

In most patients, the primary infection heals to leave a small scar visible on radiograph.Mycobacteria remain alive inside the phagocyte.

Mild immune deficiency leads to reactivation, as we said in losing a spouse for

example usually in the upper parts of the lung.

Severe immune deficiency leads to more widespread infection which is likely to

spread beyond the lungs.

Remember in M.tuberculosis it is TH1 activity, it means INF gamma in particular is

going to be produced here. Milliary tuberculosis (dissemination) and reactivation if the

bacteria present in the macrophages could not be killed and they stayed in our body.

We call that latency it is “delayed” somehow, and if our immune defenses for one

reason or another dropped like for example we get exposed to chronic stress, and here

we talk about the old man who lost his wife or the old wife who lost her husband

“losing a spouse” we call that then Mineralocorticoids will be released and so our

immunity will be suppressed so we get what we call reactivation of a primary TB or

latent TB and so the disease will start to be open and damage will take place in the area

where those were located in the beginning.

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So here when we talk about M.tuberculosis we are talking about pulmonary

tuberculosis mainly. And those micros they can be hanged in the air as I said for a

longer period of time that’s why we have to have what we call respiratory isolation,

we should be using masks all the time because we could be inhaling those organisms

that could go to the into the alveoli and induce the chronic granuloma, and usually wesee those in the upper part of the lungs, where oxygen concentration is high.

When we are exposed to those, a granuloma develops (activation of macrophages), then

we can test for those in a test we call it the PPD – the Purified Protein Derivative. This

is one example to see if we are sensitized or not, and if you remember in the

microbiology course we talked about what does it mean to have a positive PPD testing,

how we do the PPD testing, we inject the PPD protein, the Purified Protein Derivative

intradermally, why interdermally? Because we do have Langerhans cells

(macrophages) there, we want them to be activated and then we just draw a circle &

write the date and time and we read that from 48 to 72 hours- two to three days- till thechronic inflammation develops and the granuloma. so you will see a thickening and

then you will measure the diameter of the thickening, if it is 10 or more, it is positive, if

it is 5 or less then it is negative, and between 5 and 10 it is intermediate, and nowadays

any thickening they consider it positive but you have to take it in consideration with the

case of the patient, if the patient is on steroids, weather you are vaccinated or not,

infected in the past or not.

And at the same time you can measure even the level of cytokines; IL-1 and IFN

gamma which is produced when TH1 cells are activated. If the level of IFN gamma is

so high, this is an indication that you have granuloma and a chronic inflammation. So

remember M.tuberculosis and the destructive effect to the tissues is because of the

granuloma rather than the direct effect of the organism itself .

Remember what a granuloma is, macrophages in the centre with the bacteria

engulfed and TH1 cells producing cytokines INF gamma to activate the

macrophages to kill the mycobacteria.

So this is the whole process how the granuloma develops when we get infected with

M.tuberculosis, the bacteria is going to bind to toll-like receptor on macrophages and

then the cytokines are produced and we can follow that up in 12-24 hours and how theycall upon the macrophages to come into the area, TH1 cells produce cytokines (INF

gamma), IL-6, IL-8 and the granuloma is formed.

So this is the test I was telling you about here to check for the presence of INF gamma,

here mycobacterium peptides are added to a blood sample, so if you have the

macrophages, then you will be seeing lots of INFs that are produced in a patient

exposed to M.tuberculosis. In a patient who has never been exposed, there are no

suffiecient numbers of TH1 cells to produce INF gamma, so measurement of INF is an

indication of TH1, exposure to antigens of M.tuberculosis.

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So this is the PPD testing, it has to be intradermal, and we have to use vita

international units; we call that vita international tuberculin units, we inject them

intradermally, then we wait for 48 or 72 hours then we measure not the redness but the

thickening, you touch it and see the thickening and the measurement of the thickening

indicates here the granuloma.

Hepatitis is exactly the same as tuberculosis. Here we have viruses the infect the

hepatocytes, they increase in number within the hepatocytes, cell-mediated immunity

will call upon T-helper calls to come into the area and macrophages, and T-cytotoxic

cells that will start to get rid of that, so the infection will be cleared by the T-cytotoxic

cells and many interferons (particularly interferon alpha) and other cytokines will be

produced and they are going to damage the liver, leaving behind liver failure.

In hepatitis treatment we start by giving interferon alpha hopefully that we interfere

with the growth of the virus; it inhibits viral replication and have fewer inflammatory

effect than the interferon gamma which is the one the comes out of the activated

macrophages as an outcome and it is supposed to produce MHCs and more of T-

cytotoxic cells but one of its side effects is the damage of hepatocytes (by TNF) but

with interferon alpha the effect is much less, that's why we use interferon alpha for the

treatment of the chronic hepatitis caused by hepatitis virus B. OR we can vaccinate; we

can give antibodies against the hepatitis B surface antigen hopefully that the virus will

be neutralized; the antibodies are going to bind to the virus preventing its attachment to

the liver cells. So if we are injected accidently with a needle from a patient who has

hepatitis, the passive vaccine is the only thing that we can do; antibodies against the

hepatitis B surface antigen, so these antibodies are going to bind to the virus and

neutralize.

One student asked: can hepatitis B cause granuloma? In the sense of the mechanism of

the delayed type hypersensitivity YES! where here we are talking about activated

macrophages and the production of interferon gamma and those are the ones that are

going to damage the liver, maybe the mechanism is a little bit different because they are

viruses (we have T-cytotoxic cells) but activated macrophages can damage cells yes.

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Chapter 23

Cytokines in the immune system

So now the integrated from that we have an innate immune response and we have an

adaptive immune response. The innate the one that is fast, do not have memory, notspecific, complement can be activated, phagocytosis and so on, and gives warning

signals to the adaptive immune system that we have been attacked. So we have a

relationship between the innate and the adaptive and there must be some

communication pattern between them which occurs by molecules and these molecules

are cytokines.

If cytokines are produced from lymphoid cells we call them lymphokines, if they are

produced from WBCs we call them interleukins, we have interferons which interfere

with viral replication, we have Tumor Necrosis Factor which causes, as its name

implies, apoptosis of the virally infected cells and tumor cells, but the overall name forthese are cytokines.

Cytokines are mediators, cells communicate through those between the innate and the

adaptive immune system. Macrophages in the innate, for example, when they get

stimulated by the toll-like receptors they produce these cytokines that will act on the

adaptive, so the adaptive can be stimulated warning the we have been attacked, so the

signaling that takes place on the innate and the adaptive cells because of the cytokines.

So cytokines are the molecules that do the communication between the cells; in the

adaptive and the innate.

Cytokines are proteins, usually they are produced when the cells are stimulated, and

they act upon receptors; when the molecule binds to its receptor the cell will be

activated and produce the act. Some of these receptors are not there, but the minute

these cytokines are produced they activate the production of the receptors. Those

cytokines could act on the same cell that has produced it, we call that autocrine

reaction or on the neighboring cells and we call that paracrine reaction.

Chemokines are cytokines involved with chemotaxis. Chemokine receptors are

receptor on cells where the cytokines which are involved in chemotaxis act upon.

Cytokines can be activators or suppressors. Activators: cause up-regulation like IL-2,

IL-4. Suppressors: cause down-regulation like IL-10, TGF-beta, with temporary

receptors to perform the suppression then these receptors disappear; we don't want the

effect continuously.

We have the interferons (alpha, beta and gamma) which are also cytokines. Interferons

alpha and beta are involved in controlling viral infections and gamma in the activation

of macrophages, expression of MHCs.

TNF: in fever and causes damage to cells and apoptosis as well.

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Cytokines are not just produced by inflammatory cells, they could be produced from

non-inflammatory cells, so when a cell is damaged those could be produced as a sequel

to that.

Very important point to remember is that cytokines are secreted at low levels when

needed and the low levels usually like a maintenance dose for those cells for the

interaction. The minute we see them produced at high levels, that means that we have

an extraordinary interaction is taking place.

Redundancy: it means that we have cytokines that share the same function like TNF

and interferons. One form of the clinical significance of knowing that the cytokines are

redundant is that in many autoimmune diseases I need to block the production of TNF.

If I use monoclonal antibodies against TNF, I'm supposed to clear the problem because

in autoimmune diseases this is where we are going to have chronic inflammation where

it's not needed, but you'll see when we block the TNF, things will improve but it will

not be cleared completely because we have other cytokines that perform the same

function like IL-1. So till now things are not perfect as we want it to be.

Pleotropism: it means that one cytokine can act on many cells.

Finally the professor decided to stop

Dear colleagues, find a way to live your life, that it doesn’t make a mockery of YOUR

values, it’s better to be hated for what you are than to be loved for what you are not!

And remember to carry your personality with you wherever you go! " ... "

Dua’a Herzallah ™

(You can skip this part if you want :P):

Dima BaniEssa, Dima Dima Dima <3 I can’t thank you enough my dear sister <3, youare absolutely one of your kind Thank you for everything!

& to my everyday partner and soul sister, Samah Abu Omar (SEAomar), I dedicate

this special dabsheh for you: <3<3

W a5eeran wa laysa a5eran, my dear little cute loquacious Mais Z3ieter ;)) thank you

for helping me and tolerating the agony of summarizing with me, lots of love!

Best of luck to you all my lovely friends <3Thanks folks!

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