Immune system is the protection mechanism inside our body, made up of complex network of specialized cells and organs, designed to defend us against millions of bacteria, microbes, viruses, toxins and parasites that would love to invade our body. When functioning properly, it fights off infections by agents such as bacteria, viruses, fungi and parasites. When it malfunctions, it can unleash a number of diseases from allergy to cancer to AIDS.

Immune system is as complex in intricacies as of brain and nervous system and displays more characteristics. It can distinguish between ?self? and ?non-self?.
 
 
How the Immune system works:

Basically, the blood circulating with in our bodies consists of RBC, which mainly carry oxygen around the body; and WBC, which defend us. With in those WBC is housed a variety of cells that make up of immune system-

• Macrophages (big eaters) : are the generals of the army, highly intelligent and also great scavengers.
• Lymphocytes : are the second in command, are formed with in our bone marrow (jelly like substance in long bones, where blood is formed). However, a remarkable phenomenon occurs as they leave there and moves either to our Thymus or to our intestine, where they will start to mature. Thus we have T-lymphocytes and B-lymphocytes, each carrying out quite different functions.
  1. T-lymphocytes-   they mature in Thymus (a gland behind the chest bone). There are actually different types of T-cells and they not only organize many immune functions but also major factor in protecting us against the development of cancer ,autoimmune disorders such as Rheumatoid arthritis, allergies etc.
  2. B-lymphocytes-they mature in intestine and go on mature into cells that secrete a number of different proteins, known as antibodies.
• Natural killer cells: are small and armed with granules inside the cell,  which, like bullets, penetrate the cancer cells and destroy it.
   

Internal communication
                                            
Internal communication is done by a complex method of chemical messengers. When the macrophages recognize bacteria, viruses or cancer cells, they release numerous chemicals known as Cytokines. Among these a yet another family called, Interleukins which cause immune cells to mature quickly. They also produce Inflammation, which increases blood flow and heat to the affected area, leading to those aches and pains.

B-lymphocytes produce specific chemicals, or antibodies, which will fight disease. There are 5 different kinds of B?cells?

IgG, IgA, IgM, IgE and IgD

 
(Ig  -- abbrevation of Immunoglobulin. Which is synonym for Antibody)

Once an attack on the body has been successfully repelled, not all the Immunoglobulin or Antibody disappears. Some of them will stay around, rather like a peacekeeping force after a war. Immune system never forgets an encounter and the information on how it dealt with it is stored away. If at a later time that some invader appears again, it knows exactly what to do.

What happens when the immune system breaks down?
This we will discuss in next issue.