INTRODUCTION TO IMMUNOLOGY

Inside our body, we have an amazing protection mechanism called the immune system, which is

designed to defend us against millions of bacteria, viruses, fungi, toxins and parasites.

However, this system is not perfect, and sometimes it fails.

For instance, a germ can sometimes invade successfully, making us sick.

Or, instead of getting rid of pathogens, our immune system may sometimes attack our own body

components by mistake, if this happens in your joints, you may develop rheumatoid arthritis.

Alternatively, our immune system may overreact to certain antigens such as pollens.

If this happens in your respiratory tract, you may develop hay fever, which is one of the most

common type of allergy in developed countries.

One important thing to remember concerning the immune system is that it is a system, but not a

single entity.

As you may realize by listening to my talk, our immune system is actually a collection of

many different organs, special cells, and substances, which collectively help protect you from

infections and other diseases.

So, in order for the immune system to function well, it requires balance and harmony among the

various cell types and humoral factors that comprise the immune system.

First of all, let me remind you what "immunity" means.

This word actually derives from the Latin "immunis", which means exemption from military

service, tax payments and other public services.

But nowadays, immunity means more like exemption or protection from disease.

In other words, immunity is defined as resistance to disease, specifically infectious disease.

Now, let us look at the importanc
e of the immune system.

First of all, the immune system is important because it defends us against infections.

This point becomes clearer if you look at the people who have been born with problems with

their immune system, a condition called "immunodeficiency".

These immunodeficient people can become infected very easily and often die of such infections.

So, this tells us how important it is to have an intact immune system.

Second, the immune system is important, because it works as defense against newly arising

transformed cells, such as malignant tumor cells.

The fact that the immunodeficient patients are also prone to develop various types of tumors

underlines the importance of the immune system.

Third, elimination of non-self, such as newly introduced substances or molecules, or tissue

grafts is another important task of the immune system.

Tissue grafts are normally rejected, because the recipients' immune system attacks them and

finally eliminates them.

However, if the recipient is given immunosuppressive drugs to blunt his/her immune response,

tissue graft rejection is delayed or sometimes completely inhibited, indicating the importance of

the immune system.

Finally, if the immune system works excessively, it leads to tissue injury or inflammation, as you

will see in the case of allergy and autoimmune disease.

This slide shows you an amazing capability of our immune system.

By properly stimulating the immune system using part of pathogens or vaccines, we have been

able to dramatically reduce the incidence of certain infectious diseases in developed countries.

This is particularly the case with childhood diseases, such as measles, rubella, mumps and

polio, which were highly prevalent among children some decades ago.

However, subsequent to the development of specific vaccines against them, these diseases are

declining very rapidly, and you hardly see them among properly vaccinated children.

So, this clearly shows the strength of the immune system.

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