Re: Role of white blood cells

In today's society we are constantly exposed to bacteria and viruses.  It 
often appears as if our body is poorly equipped to fight off these 
infections.  While the immune system cannot fight all infections 
equally, _it is_ capable of fighting off many infections.

Some background on antibiotics.  First of all, antibiotics serve an important 
role in treating many bacterial infections.  Indeed, the discovery of 
antibiotics earlier this century truly revolutionized the outcome 
of certain bacterial infections.  However, antibiotics are only effective 
against BACTERIA, NOT VIRUSES.  Moreover, not all antibiotics are equally 
effective against all bacteria.  For example, penicillin works wonderfully 
against certain bacteria, but does not have any effect on other bacteria.  
Unfortunately, today, many bacteria have also become resistant to antibiotics 
used previously to treat bacterial infections.  Penicillin is often not 
effective against bacteria that it used to treat quite effectively.  This has 
prompted great interest in finding new antibiotics.  You can find further 
background on antibiotics at Bugs in the News.

While antibiotics are effective against bacterial infections, they have 
_NO_ effect on viral infections.  Indeed, there are few available anti-viral 
treatments (one such example being the protease inhibitors used in treating HIV 
infection).  Anti-viral therapy has been difficult to develop because viruses 
rely on much of our own internal machinery to survive.  Because of this, it is 
difficult to specifically kill the virus and not harm the person.

Why have antibiotics been so helpful in the past and present? In some cases 
our immune system is not very effective at clearing certain infections.  
Why?  Bacteria and viruses have a much shorter generation time than humans. 
Some bacteria can divide every 20 minutes.  A single virus infecting one 
cell can produce hundreds of new viruses.  This short generation time and 
the large number of "offspring" help bacteria and viruses adapt VERY 
quickly to human defenses.  There are many examples of how a pathogen (a 
pathogen is a bacteria or virus that causes disease) has developed 
strategies to manipulate and subvert our normal defenses.  Some pathogens 
today are EXTREMELY well adapted to surviving within us.  Others are still 
adapting and changing.  HIV, for example, is constantly undergoing slight 
changes which makes it a very difficult target for our body to kill.  This has 
also complicated the development of an effective drug therapy against HIV.  

Because of the adaptations that pathogens have evolved, I consider it 
truly amazing that our immune system can fight off bacteria and viruses.  
Unfortunately, the immune system is not always successful, even with its 
tremendous complexity and multiple lines of defense.  Please realize that the 
immune system is important despite its occassional shortcomings.  Examples of 
the importance of a functional immune system include:

1) Immunization (Vaccination).  
Given the chance, our immune system can destroy pathogens quite 
effectively.  In some cases, the pathogen spreads so quickly that the immune 
system does not have enough time to contain the threat.  Immunization (also 
referred to as vaccination) is a technique that helps our immune system respond 
to a pathogen more quickly and strongly.  Without vaccination, a person's immune 
response might not be fast enough to stop the pathogen.  Through the use of 
vaccination, many diseases that were once terrible threats to human health no 
longer pose significant health threats to immunized individuals.  Smallpox, 
polio, and measles are all examples of diseases which have been diminished by 
the use of vaccination.  A short article on vaccination can be found at ChildSecure.


2) Immune-deficiency.
In the past two decades, people have come to appreciate the importance 
of a functional immune system in order to maintain a healthy everyday 
life.  First, AIDS and HIV infection has created an enormous number of 
people who no longer have an intact immune system.  People with acquired 
immunodeficiency often become sick from infections that do not affect the 
general population.  Many of these infections are considered "opportunistic 
infections", which means that an intact immune system can normally contain 
and prevent such an infection.  For AIDS patients, however, the immune 
system is no longer capable of containing such an infection.  Note that 
AIDS patients don't actually die of the HIV infection.  They die, instead, 
from a secondary infection initiated by a compromised immune system.

Transplant recipients typically receive immunosuppressive drugs to reduce 
the chance of rejecting their transplant.  When on a heavy dose of 
immunosuppressive therapy, these patients have a similar propensity for 
opportunistic infections.

Both of the above situations involve individuals who acquire immunodeficiency 
(through infection or through the use of immuno-suppressive drugs).  A final 
example of the importance of a functional immune system has come from the 
handful of patients with Severe-Combined Immunodeficiency Disorder (SCID).  
These patients are born without a major component of the immune system and are 
EXTREMELY susceptible to infection.  Indeed, SCID patients cannot survive if 
exposed to the normal level of bacteria and viruses that we encounter every day.  
The "Boy in the Bubble" was a SCID patient.  He had to live inside a 
plastic bubble that protected him from the bacteria and viruses present in 
the surrounding environment.  Even with such protection he died at a very 
young age.  More information on SCID patients can be found in a press release 
about possible
therapies for very young SCID patients as well as at a web-site created by 
the mother of a SCID patient
.

I hope that the above examples stress the importance of a functional immune 
system for a comparatively healthy, everyday life.  In the case of 
pathogens which are particularly good at escaping destruction by the immune 
system, tools such as vaccination and antibiotics can help our immune 
system win the battle.


ETC