The immune system is a complex network of cells and organs that protects the body from foreign invaders. It recognizes and remembers millions of antigens like bacteria, viruses, and fungi. The immune system differentiates between the body's own cells and foreign cells to target the latter for destruction. Infections are a major cause of disease, as microbes try to enter through openings in the skin or internal passages, but the immune system provides defenses against such pathogens.

1. How our Immune System Works?
Summary
The immune system is a complex mechanism that can recognize and remember millions of
different antigens, and subsequently can produce secretions and cells that could match up
that particular trigger and thus, can destroy them. The key to a healthy immune system is
its noteworthy ability to differentiate between the body’s own cells- self, and foreign cells-
non-self.
The most common cause of human disease is infections. They range from common cold to
weakening conditions such as chronic hepatitis and life-threatening diseases such as AIDS.
Microbes (pathogens) causing disease that try to get into the body must first move past the
external armor of the body, usually the skin or cells lining the internal passages of the
body. The skin provides an impressive barrier to microbes invading. It is usually only
penetrable by cuts or small abrasions. Both the digestive and respiratory tracts are
entrance portals for a number of microbes. They also have their own protection levels.

3. What is Immune System?
The immune system is a complex network of cells, tissues, and organs working together to defend our body against
the attacks by “foreign” invaders, known as antigen that triggers bodies’ immune response. These antigens primarily
include microbes (germs), infection-causing organisms like bacteria, viruses, parasites, and fungi.
The duty of the immune system is to protect us from theses invading microorganisms. This vital task falls to a complex
range of highly expert cell types spread throughout the body but working together as an integrated system.
How Immune System Works?
The amazingly complex immune system can recognize and remember millions of different antigens, and can produce
secretions and cells that could match up that particular trigger and thus, can destroy them. The key to a healthy
immune system is its noteworthy ability to differentiate between the body’s own cells- self, and foreign cells- non-self.
The organs, responsible for the immune system are located throughout the body. They are known as lymphoid
organs, which are home to lymphocytes or white blood cells. They are the key players in body’s immune system.

4. Immunity might be strong or weak, short-term or long-lasting, dependable on the sort of antigen, the volume of antigen, and the path through
which it enters the body.
Immunity is also influenced by inherited genes. When we are faced with the same antigen, some of us will respond forcefully, others feebly,
and some not at all.
An immune response can be generated not only by infection or antigens but also by immunization with vaccines. Vaccines contain a particular
amount of microorganisms or parts of microorganisms that have been treated, so that they can provoke an immune response but not the full-
blown disease.
Immunity can also be transferred from one person to another by injections of serum rich in antibodies against a particular microbe
(antiserum).
What is Immune Tolerance?
Immune tolerance is the affinity of T or B lymphocytes to ignore self-tissues of the body. Maintenance of tolerance is necessary because it
prevents the immune system from attacking its fellow cells. Tolerance occurs in minimum two ways- central tolerance and peripheral tolerance.
Central tolerance occurs at the time of lymphocyte development. At the very early stage of immune cell’s life, it is visible to many of the self-
molecules in the body. If it encounters these molecules before being fully matured, an internal self-destruct pathway is activated and the
immune cell dies.
In case of peripheral tolerance, circulating lymphocytes can recognize a self-molecule but cannot make response because some of the chemical
signals, necessary to activate the T or B cell remain absent.

5. Key Points
• The immune system protects us from invading microorganisms,
known as antigen.
• The antigens primarily include microbes (germs), infection-causing
organisms like bacteria, viruses, parasites, and fungi.
• The organs, responsible for the immune system are known as
lymphoid organs that contain lymphocytes or white blood cells.
• Immunity might be strong or weak, short-term or long-lasting.
• Immune tolerance is the affinity of T or B lymphocytes to ignore self-
tissues of the body.
Published by Brainware University