Gut flora and its function with immunity system

1. Gut flora and its role in
immune function
BY
ST.DR: HARITH RIYADH
AKAKI TSERETELI ATSTE UNIVERSITY

2.  Although the main functions of the digestive
system were once believed to include little
beyond the breakdown of food into usable
energy for the body and elimination of waste,
the digestive tract is also home to 100 trillion
microorganisms, known as the gut flora
 The majority of these microorganisms are
bacteria, with a small percentage consisting
of fungi and protozoa.

3.  1.) Essential Flora: This is the "friendly" bacteria that is found in
the gut. In the healthy individual, essential flora dominates and controls
other types of less desirable microorganisms. When functioning
normally, this type of flora is responsible for conducting numerous roles
that keep the body healthy.
 2.) Opportunistic Flora: This group of microbes is found in the
gut in limited numbers that are strictly controlled by the essential flora
in the healthy individual. This type of flora is capable of causing disease
if the essential flora becomes compromised and is unable to control the
growth and numbers of opportunistic flora.
 3.) Transitional Flora: These are various microorganisms that are
introduced into the body through eating and drinking. When the
essential flora is healthy and functioning normally, this type of flora will
pass through the digestive track without causing harm. However, if the
essential flora is damaged, this group of microbes can cause disease.

4.  Although there is still much to be learned about the role
of gut flora in immune function, it is becoming
increasingly clear that disease (and health) really does
begin in the gut! Studies have shown that the gut flora has
a profound influence on the development and maturation
of the immune system after birth (Bouskra et al., 2008;
Macpherson & Harris, 2004). In addition, it has been
estimated that approximately 80 -85% of the immune
system is located in the gut.

6.  In the healthy individual, the essential gut flora forms a bacterial
layer that covers the entire digestive track. This bacterial layer
acts as a physical barrier to protect against transitional flora ,
viruses, parasites, toxins, and undigested food particles. The
gut flora produces acids that lower the pH of the gut wall and
make it undesirable for microbes that cause disease. The
essential flora also has the ability to neutralize many toxins and
inactivate carcinogens (substances known to cause cancer). It
also plays a direct role in suppressing the processes by which
cancer cells are known to develop and grow

8.  The essential flora has a direct effect on important
immune functions because it is responsible for stimulating
the tissues of the lymph system that are located in the gut
wall to produce lymphocytes, a type of white blood cell
that fights infections. The lymphocytes then produce
immunoglobulins, which are antibodies formed in
response to contact with foreign substances (viruses,
bacteria, fungi, etc). The immunoglobulins destroy and
inactivate invading substances that enter the body through
food and drink

9.  The essential flora also has a direct impact on the function
and/or production of other many other cells of the immune
system. When the essential flora is damaged, immune function is
affected not only in the gut, but systemically as well (throughout
the entire body). Specific to autoimmune disease, essential gut
flora plays an important role in the development of regulatory T
cells, a critical component of the immune system. The types,
number, and balance of regulatory T cells are directly influenced
by the essential gut flora. The dysfunction of the regulation of
different types of regulatory T cells (an imbalance in certain
kinds of T cells) is responsible for the development of
autoimmune disease.

10.  A broader explanation of how the gut flora influences immune function is
by understanding the balance between the two arms of the adaptive
immune response, known as Th1 and Th2 immunity.
 In general, the role of Th1 immunity is to fight infections in the skin,
mucous membranes, and cells. When the essential flora is damaged, the
production and function of Th1 cells becomes impaired, allowing more
invaders into the body. The body responds by overcompensating with a
Th2 response. The overactive Th2 response then predisposes the
individual to allergic-type reactions, chronic inflammation, and
autoimmunity. Healthy essential gut flora is the key to keeping these
arms of the adaptive immune system in balance, thus preventing disease.