Juz wanna ask a question about immunology. Was studying immunology these few days, as it is one of my exam topics for Biology. our immune system produces antibodies in the presence of antigens, until one of them is able to fit the protein of the antigen. i noe that for the first exposure to the antigen, it would take some time. however, why is it that diseases like cancer cannot be countered by the body's immune system?
Immunology
Well, it's not that simple for everything.
Cancer, if I'm not mistakin and I don't feel like googleing right now, is when your cells don't stop repdocuing, thus causing a tumor. What they have to do is find a way to slow those cells without stopping them, if they stop then tissue and everything else begins to decay.
Im not sure, yet again, but Cancer isn't really the immune systems fault. Now, with most viruses and bacterium, the method you mentioned is what is employed and scientists are able to artificially create the proteins needed in most instances.
Theres a lot of factors and a lot of ifs, it takes time.
Cancer, if I'm not mistakin and I don't feel like googleing right now, is when your cells don't stop repdocuing, thus causing a tumor. What they have to do is find a way to slow those cells without stopping them, if they stop then tissue and everything else begins to decay.
Im not sure, yet again, but Cancer isn't really the immune systems fault. Now, with most viruses and bacterium, the method you mentioned is what is employed and scientists are able to artificially create the proteins needed in most instances.
Theres a lot of factors and a lot of ifs, it takes time.
OK - Cancer for beginners
You need to understand a cell before it makes sense.
A cell is made up from various things - fats, proteins sugars and DNA to be specific. The important bits are protein and DNA.
DNA (DioxyRibonucleic Acid) is the famous double helix discovered by Crick and Watson (and Rosalind Franklin who never gets due credit). It is made up of two intertwining strands of matter forming one large molecule. The molecule is built from 4 bases (called nucleotides) and these are adenine (A), guanine (G), cytosine (C) and thymine (T).
Now DNA is a big molecule - the DNA from a single cell could be stretched to about 2 metres in length. For this reason it is tightly wound up (around proteins). The DNA is divided into Chromosomes - 46 in humans - which are lengths of DNA wrapped tightly round proteins to form little beads called nucleosomes. The combination of the nucleosomes in a cell is together known as chromatin and is a densly packed structure of these little beads of tightly wound DNA chromosomes.
With me so far ?
OK each chromosome is firther split into Genes. A gene is trhe fundamental unit of DNA and each gene is responsible for telling the cell how to make 1 protein. The cell functions by combining amino acids in different combinations to form proteins and these proteins control the cell and its environment. Each of the 46 chromosomes has around 30,000 genes. Each gene can be listed as a series of the 4 bases which it is made of and the listing would be something like :
AAAGCTGCTAAAGGCTA - just a long string of the letters of the bases A, G, T and C.
The order of the bases is the blueprint which tells the cell how to make the proteins and can be imagined as a pattern or a recipe book. The sequence of letters for the entire 30,000 genes and 46 chromosomes makes up the Genetic Code for a human.
Now, cancer happens when one of the proteins does not work correctly. The gene which produces the protein gets damaged and the code gets out of sequence. Instead of GGCCA, for example, it might now read GGGCA - 1 base different. This screws up the recipee and the protein doesn't work.
There are 4 types of gene in particular involved in cancer. These are :
Suicide genes - they are involved in a complex process which tells the cell to comit suicide to avoid damaging it's neighbours. The process is correctly called Apoptosis. Damage to these genes can mean the cell does not die when it should.
Oncogenes - these produce the proteins which control when a cell starts dividing and how fast it does so. Like the throttle on my motorbike controlling the speed. Damage here can mean a cell going into rapid division (replication) and producing too many copies too quickly.
Tumour suppressor genes - these produce proteins which do the opposite - they shut down cell replication. Damage here can mean the cell just carries on replicating after is should have stopped.
DNA-repair genes - these repair the damage to the DNA that happens routinely from outside sources - chemicals, physical damage etc. If these genes are damaged, the DNA becomes damaged more and more and may get corrupted enough to produce duff proteins which then interfere with the cell replication.
Cancer is, therefore, basically a malfunction in cell replication which means that the cell reproduces to fast or for too long. This often leads to a tumour which is a visible sign of the over production of cells but in some cancers the effects are more subtle.
The genes can be damaged by viruses (virii ?)i, by chemicals, by physical damage (a bang on the hand could possibly damage a cell's genes for example). If the damage is to one of these 4 types of gene then cancer can develop as the cell replicates out of control.
I hope that helps.
Here is a link to a fantastic workbook on cell structure and DNA that I found a while ago. It covers all of this in more detail and has exercises using web sites to really examine how geneticists work.
http://camres.frih.net/resources/biology/cell-structure-workbook.pdf
Regards
Chris
You need to understand a cell before it makes sense.
A cell is made up from various things - fats, proteins sugars and DNA to be specific. The important bits are protein and DNA.
DNA (DioxyRibonucleic Acid) is the famous double helix discovered by Crick and Watson (and Rosalind Franklin who never gets due credit). It is made up of two intertwining strands of matter forming one large molecule. The molecule is built from 4 bases (called nucleotides) and these are adenine (A), guanine (G), cytosine (C) and thymine (T).
Now DNA is a big molecule - the DNA from a single cell could be stretched to about 2 metres in length. For this reason it is tightly wound up (around proteins). The DNA is divided into Chromosomes - 46 in humans - which are lengths of DNA wrapped tightly round proteins to form little beads called nucleosomes. The combination of the nucleosomes in a cell is together known as chromatin and is a densly packed structure of these little beads of tightly wound DNA chromosomes.
With me so far ?
OK each chromosome is firther split into Genes. A gene is trhe fundamental unit of DNA and each gene is responsible for telling the cell how to make 1 protein. The cell functions by combining amino acids in different combinations to form proteins and these proteins control the cell and its environment. Each of the 46 chromosomes has around 30,000 genes. Each gene can be listed as a series of the 4 bases which it is made of and the listing would be something like :
AAAGCTGCTAAAGGCTA - just a long string of the letters of the bases A, G, T and C.
The order of the bases is the blueprint which tells the cell how to make the proteins and can be imagined as a pattern or a recipe book. The sequence of letters for the entire 30,000 genes and 46 chromosomes makes up the Genetic Code for a human.
Now, cancer happens when one of the proteins does not work correctly. The gene which produces the protein gets damaged and the code gets out of sequence. Instead of GGCCA, for example, it might now read GGGCA - 1 base different. This screws up the recipee and the protein doesn't work.
There are 4 types of gene in particular involved in cancer. These are :
Suicide genes - they are involved in a complex process which tells the cell to comit suicide to avoid damaging it's neighbours. The process is correctly called Apoptosis. Damage to these genes can mean the cell does not die when it should.
Oncogenes - these produce the proteins which control when a cell starts dividing and how fast it does so. Like the throttle on my motorbike controlling the speed. Damage here can mean a cell going into rapid division (replication) and producing too many copies too quickly.
Tumour suppressor genes - these produce proteins which do the opposite - they shut down cell replication. Damage here can mean the cell just carries on replicating after is should have stopped.
DNA-repair genes - these repair the damage to the DNA that happens routinely from outside sources - chemicals, physical damage etc. If these genes are damaged, the DNA becomes damaged more and more and may get corrupted enough to produce duff proteins which then interfere with the cell replication.
Cancer is, therefore, basically a malfunction in cell replication which means that the cell reproduces to fast or for too long. This often leads to a tumour which is a visible sign of the over production of cells but in some cancers the effects are more subtle.
The genes can be damaged by viruses (virii ?)i, by chemicals, by physical damage (a bang on the hand could possibly damage a cell's genes for example). If the damage is to one of these 4 types of gene then cancer can develop as the cell replicates out of control.
I hope that helps.
Here is a link to a fantastic workbook on cell structure and DNA that I found a while ago. It covers all of this in more detail and has exercises using web sites to really examine how geneticists work.
http://camres.frih.net/resources/biology/cell-structure-workbook.pdf
Regards
Chris
That sounds like what I said...I think.
| HoboBarticus wrote: |
| That sounds like what I said...I think. |
Hey, man, no criticism of your answer was intended or justified. It is accurat and concise. I banged out my answer off-line as I sometimes do when busy so it was not meant to suggest yours was faulty or insufficient..I just didn't see it until I was ready to post and then I thought I may as well, if only for the link
chris
| orcaz wrote: |
| Juz wanna ask a question about immunology. Was studying immunology these few days, as it is one of my exam topics for Biology. our immune system produces antibodies in the presence of antigens, until one of them is able to fit the protein of the antigen. i noe that for the first exposure to the antigen, it would take some time. however, why is it that diseases like cancer cannot be countered by the body's immune system? |
So, I hope I can reply knowledgeably to this, since I am doing research in this area now.
(1) Your statements about antibody production are correct.
(2) The body DOES produce antibodies against tumor cells.
(3) Previous posts have addressed an important part of cancer biology: the deregulation of cell growth. Another important aspect of cancer biology is brought up by your question: the deregulation of a normal extracellular environment.
Now to expand on those three points.
#1 and #2: Tumors make different proteins than healthy cells in order to stimulate blood vessel growth and in order to propagate their own growth. These molecules, when exposed to dendritic cells, macrophages, or lymphocytes (all parts of the immune system), can be recognized as "abnormal" or "foreign." Sometimes it is the quantity of a molecule and not just the type of molecule that activates the immune system. This would lead to activation of the immune system and destruction of the abnormal cell. This is going on right now in all of us. Sometimes, however, the abnormal cell has further mutations. The abnormal cells can secrete chemical messengers that upregulate those cells that suppress immune responses and downregulate those cells that carry out the immune response. They can also downregulate the molecules (known as major histocompatibility complexes, or MHC) that normally present "foreign" things to the immune system, thereby avoiding the immune system.
Since the 1990s, researchers (including my lab) have worked on changing these effects on the immune system and giving people "vaccines" that activate their immune system to respond to tumors. For example, PC6.1 is a drug that kills regulatory T cells. Regulatory T cells normally suppress immune response and do so more avidly in the tumor microenvironment. Vaccines are then applied that essentially deliver molecules commonly found in certain tumor types (such as "carcinoembryonic antigen" or CEA in colon cancer) to the body coupled with a piece of virus that won't hurt you but will trigger an immune response. While these therapies are effective to an extent, they are not 100% effective. Anything less than 99.999% efficacy in killing tumors allows for the possibility of recurrence. Current research is underway in my lab and other labs to identify more ways to enhance this strategy.
#3 Another way tumors change their environment to thrive is by increasing blood vessel growth. Oxygen only diffuses so far through tissues. Tumors cannot grow beyond 1-2mm in size without new blood vessel growth to get oxygen to them. So, successful tumors produce the chemical messengers necessary to cause new blood vessel growth. One of them, vascular endothelial growth factor (VEGF), has been targeted by medications for a number of years, the most common being Avastin. Avastin in combination with other chemotherapies has shown pretty good (but clearly not completely adequate) success against several types of cancer. Here's an interesting spin. VEGF produced by tumors not only increases blood vessel growth but decreases the ability of macrophages and dendritic cells to activate the immune system in response to tumor cells. Some researchers have begun studying whether inhibiting VEGF with Avastin can help the immune system fight off the cancer or help improve the work of the cancer vaccines.
As someone in the field properly please feel free to chuck rocks or otherwise dismantle abuse or deride my efforts above. As a non biologist I haven't got much clue about genetics etc but I thought that a broad picture was needed to get a handle on the various bit of terminology and various concepts. I'm aware that it is probably over simplistic or even wrong, so I'm always very happy to be corrected by a pro in the field
Chris
Chris
I feel smarter after reading this thread! thank you : )
I was wondering though (a little of subject but) what is holding scientest and doctors back from creating a cure for disease caused by viral infections such as hiv and or aids?
It just sounds like it should be much simpler considering the nature of the disease compared to problems like cancer.
A little more on subject, what have doctors and scientest found to be the cause of such mutations as those present in cancer?
I could probably look this up myself, but then the oportunity for my more educated frihost alies to make an educational post would be lost : )
I was wondering though (a little of subject but) what is holding scientest and doctors back from creating a cure for disease caused by viral infections such as hiv and or aids?
It just sounds like it should be much simpler considering the nature of the disease compared to problems like cancer.
A little more on subject, what have doctors and scientest found to be the cause of such mutations as those present in cancer?
I could probably look this up myself, but then the oportunity for my more educated frihost alies to make an educational post would be lost : )
| Quote: |
| I was wondering though (a little of subject but) what is holding scientest and doctors back from creating a cure for disease caused by viral infections such as hiv and or aids? |
Once viruses enter our bodies, they attach to cells, find their way inside (sometimes by tricking the cells), and use the stuff inside the cells, usually reserved for the cells' own function, to replicate themselves. There are many variations on this theme. Some viruses replicate quickly and burst open the cells they have infected so that they can spread to other cells. Some viruses replicate slowly and do not burst out of cells as quickly. Some viruses do not destroy the cells at all, but have special ways of budding from cell to cell. Viruses also have different ways of storing and replicating their information and different ways of using the host cell's functions.
As you can see, there is a wide variety of ways that viruses operate in our bodies. As a result, it's not simple to have one way of responding to them. Our immune cells need to see some sign that there is an enemy there - either encountering the virus in the blood when it is outside a cell or encountering something on the surface of a cell that indicates it has viruses inside. Even with that recognition, there is no guarantee that we can clear all the little virus particles as long as they are replicating quickly and hiding inside our cells.
It may interest you to know that we only have a few good ways of treating most viral illnesses - the major one being vaccinations. We inject people with the parts of the virus that the body would recognize in an infection. This way we give the immune system the chance to prepare in advance for an infection, allowing us to fight it off much more efficiently before the virus replicates so much that there is a lot of virus to clear. We also have medications that inhibit the way the viruses reproduce themselves. The viruses have a trick though. You see, the processing of reproducing genetic material, especially for viruses, is not a perfect one. Errors happen. Sometimes these errors change the proteins that virus is made of. If it's a protein that the immune system was targeting, a change means that now the virus won't be recognized by the immune system. Similarly, changes in the virus that change the targets of our medications will lead to the medications not working.
In the case of the human immunodeficiency virus (HIV), we have a virus that uses proteins on its surface to bind to a receptor commonly found on several cells in our immune systems. This tricks the cell into letting the virus inside. Normally, our cells have DNA, from which they make RNA, which is then used to make proteins. DNA can also be replicated. HIV carries only RNA. It has a special molecule that changes the RNA into DNA. Once it has done that, the normal cell process of DNA --> RNA --> Protein can take place, replicating the proteins and RNA of the virus. HIV is one of those tricky viruses though that will hide for a very long time inside cells, so not only does it use a non-traditional mechanism to replicate itself, but it also is hard to clear from the blood because it hides so well. To make matters EVEN worse, because it attacks immune cells, it actually reduces the effect of the immune system.
So how are we treating it? We have several classes of medications that target different parts of the HIV's lifecycle. However, HIV undergoes these errors rapidly (also called mutations) and can become resistant to our medications.
The modern course of HIV infection goes like this:
* An initial infection causes flu-like illness and a drop in CD4 T cells (the ones that are targeted the most by HIV).
* Everything rebounds slightly after the first few weeks, but not back to normal.
* For years and years, HIV replicates slowly and the number of CD4 T cells declines very slowly.
* When the CD4 count drops below 350 (for most physicians, some still stick to 200), treatment begins. This is because that is a point where there is enough virus activity to actually be affected by the drugs, rather than just hiding.
* We treat with 3 medications at a time, using some different classes of medicine, so that lines of mutated virus can't develop as quickly. A virus might get a mutation that protects it from one drug, but as long as another drug keeps it from replicating, that mutation never survives.
* If someone's condition progresses, we can test for resistance to our medications and try new medications
* If a person's disease progresses enough where they get sick because their immune system is very depleted or if their CD4 count drops below 200, they are considered to have AIDS (acquired immunodeficiency syndrome).
Right now, a patient with good healthcare can live with HIV for 10, 20, maybe 30 or more years before developing AIDS. Since we have medications for the sicknesses that most commonly affect people with AIDS, called opportunistic infections, we can often keep them from dying as soon even if they do progress to AIDS.
But the virus still hides and it hides very well. We just don't have anything that is effective enough to eliminate every last one. Perhaps there will be a cure in the future, but the encouraging thing now is that if we can teach people how to avoid spreading it and get the medications we do have to the people who need it, we could drop the death rate from HIV/AIDS dramatically.
| Quote: |
| A little more on subject, what have doctors and scientest found to be the cause of such mutations as those present in cancer? |
Cells in our body replicate all the time. They do this by replicating their DNA, the molecule that encodes the basic genetic information, and then dividing it into two new cells. They replicate because cells get old and eventually die and need to be replaced by new cells or they replicate because the body needs more cells in some area. In either case, they receive messages that this is the case from molecules floating around in the body. Cells can also receive signals that they should die and not grow.
So what goes wrong in cancer? It takes a combination of things:
* Normal regulation of when to replicate is replaced by uncontrolled replication (signals to grow are constantly activated or signals to die are blocked)
* Cancer cells don't respond to their environmental signals as well, so they lose control
* Cancer cells don't form the appropriate formations
* Cancer cells learn how to move to other locations by breaking their linkages to their current locations and by establishing connections to new locations
It all comes down to how all the little molecules that govern a cell's daily function work. Just like viruses can have mutations, so can our cells. Since our cells are always reproducing *normally*, if there is an error in the process that replicates DNA, then you get mutated DNA. This is thought to be the mechanism behind evolution - where organisms get new traits that help them survive in new ways. However, just the same, if that mutation does something bad, it can lead to death or cancer.
DNA replication errors occur at a frequency of 1 per every 1 billion replications. Considering that we have at least 10 trillion cells in our body, that means if every cell replicated just once, we would get 10,000 mutations. And as I mentioned above, there are just a few key changes that have to take place to lead to cancer. There are parts of the environment that affect this too. When UV rays damage our DNA or when dangerous molecules we've ingested damage our DNA, this increases the number of mutations that can and will happen.
Theoretically, if we all lived long enough we'd probably all develop some sort of cancer because mutations eventually develop. Unfortunately there are parts of our genetic code and our lifestyles that make some of us more prone to having these mutations and therefore more prone to getting cancer.
wow! interesting
cancer is quite a complicated disease huh? i suppose more research on DNA would probably dig up some more efficient
cancer is quite a complicated disease huh? i suppose more research on DNA would probably dig up some more efficient
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