241. Immune System

 Have been doing some reading on the immune system and neutrophils - to do with why my Chemo's are delayed.
Thought I'd share the information, particularly as September is Lymphoma Awareness Month...

The immune system protects the body against infection by bacteria, viruses and other parasites. It is really a collection of responses that the body makes to infection. So it is sometimes called the 'immune response'.
The immune system is important to cancer patients in many ways because

• The cancer can weaken the immune system
• Cancer treatment can weaken the immune system
• The immune system may help to fight your cancer

The cancer can weaken the immune system by spreading into the bone marrow where the cells that help fight infection are made. This happens most often in leukaemia or lymphoma. But it can happen with other cancers too. The cancer in the bone marrow stops the bone marrow making so many blood cells.
Chemotherapy and radiotherapy can weaken immunity by causing a drop in the number of white blood cells made in the bone marrow. Apart from bone marrow or stem cell transplants, this effect on the bone marrow is temporary. High doses of steroids can also weaken your immune system temporarily.
Some cells of the immune system can recognise cancer cells as abnormal and kill them. Unfortunately, this is not enough to get rid of a cancer altogether. But some new treatments aim to use the immune system to fight cancer.
There are two main parts of the immune system

• The inbuilt protection we have from birth
• The immune protection we develop from being exposed to certain diseases

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In-built immune protection

This is also called 'innate immunity'. These immune mechanisms are always ready and prepared to defend the body from infection. They can act immediately (or very quickly). This in-built protection comes from

• A barrier formed by the skin outside the body
• Inner linings of the gut and lungs which produce mucus and trap invading bacteria
• Hairs which move the mucus and trapped bacteria out of the lungs
• Stomach acid which kills bacteria that have been swallowed
• Helpful bacteria growing in the bowel which prevent other bacteria from taking over
• Urine flow which flushes bacteria out of the bladder and urethra
• White blood cells called 'neutrophils' which can find and kill bacteria and other infectious organisms

The skin forms a waterproof mechanical barrier. But it is also slightly acidic. This helps to keep bacteria out as they don't like acid. Some skin conditions cause loss of this acidity and people are then much more prone to skin infections.
There are several ways that these natural protection mechanisms can be damaged or overcome if you have cancer. For example

• Something may break the skin barrier (such as a drip or a wound from surgery)
• Chemotherapy may damage to the lining of the gut (severe diarrhoea can break down the gut lining)
• A catheter into your bladder can become a route for bacteria to get inside the bladder and cause infection
• Radiotherapy to the lung can damage the hairs and mucus producing cells that help to remove bacteria
• Antacids for heartburn may neutralise the stomach acid that kills bacteria
• Chemotherapy can temporarily reduce the number of neutrophils in the blood (the 'neutrophil count') which means it is more difficult for you to fight off infection

 

Neutrophils

These white blood cells are very important for fighting infection. They are good at fighting bacteria and fungal infections. They can

• Move to areas of infection in the body
• Stick to invading bacteria or fungi
• Swallow up the bacteria, viruses or fungi
• Kill the bacteria they have swallowed with chemicals

Your normal neutrophil count is between 3,000 and 6,000 neutrophils in each millilitre of blood. When you don't have enough neutrophils you are said to be 'neutropaenic'.
Chemotherapy and some radiotherapy treatments can lower your neutrophil count. So, after chemotherapy or radiotherapy you may be more likely to get bacterial or fungal infections (like thrush).
If you are having cancer treatment, it is important for you to know that

• Infections can become serious more quickly in people with low neutrophil counts
• Antibiotics could save your life, so if you get a fever or feel ill, phone your cancer centre or go to casualty straight away

You are most likely to become ill from bugs you carry around with you normally, not from catching someone else's. This means that you don't have to avoid your family, friends or children when you are sent home after chemotherapy.
You can ask your cancer doctor or nurse what precautions you should take against infection if you are having a lot of chemotherapy or radiotherapy. Look in CancerHelp UK's cancer drug side effects section for some tips.
When your blood counts are low, your cancer specialist may want you to take antibiotics to help prevent severe infection. We don't really know whether this approach works, but results from clinical trials may be available soon.