Innumerable bacteria and viruses constantly attack our body throughout the year. If the body does not fight against these foreign bodies we would have to suffer from so many diseases. The body’s response to these foreign bodies is called the immune response. Our skin and the mucous membrane in the nose provide the first stage protection from these foreign bodies. The stomach has many potent digestive enzymes capable of neutralizing any thing. Our white blood cells are the fighters in our blood that attack the bacteria and virus. The lymph nodes alert the body when a foreign body enters inside the body. All the fighting cells, tissues and organs form the immune system of the body.