The immune system is complex, intricate and interesting. The immune system can be described as body's defensive system or a system of biological structures and processes within an organism. It protects against disease by identifying and killing pathogens and tumour cells. Immune system is designed to defend the body against millions of bacteria, microbes, viruses, toxins and parasites that invades in our body.             It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly. Detection is complicated as pathogens can evolve rapidly; producing adaptations that avoid the immune system and allow the pathogens to successfully infect their hosts.             Once immune cells receive the alarm, they become activated and begin to produce powerful chemicals. These substances allow the cells to regulate their own growth and behavior, enlist other immune cells, and direct the new recruits to trouble spots. When the immune system hits the wrong target, however, it can unleash a torrent of disorders, including allergic diseases, arthritis, and a form of diabetes. If the immune system is crippled, other kinds of diseases result.

  There are two main fluid systems in the body: blood and lymph. The blood and lymph systems are intertwined throughout the body and they are responsible for transporting the agents of the immune system.
            The immune system is made up of special cells, proteins, tissues, and organs that work together to defend the body against germs and microorganisms every day. These special cells involve white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.

Factors that Affects the Immune System

            Scientists know that a number of factors can affect the body's immune system: poor diet, certain steroids, chronic stress. Now researchers at Michigan State University have discovered that an appetite-controlling hormone also affects the immune system.
Factors that have Good affect on the immune system:  Natural diet, happiness and serenity, high morale, a positive attitude, adequate rest and sleep, fresh air, physical exercise.
Factors that have adverse affect on immune system:

• Toxemia from dietary errors, constipation;
• Dietary deficiencies, in particular Vitamin C.

• chemicals from different sources including fluoride, chlorine, etc in water supplies, pesticide residues in food, other chemicals in food; mercury in amalgam tooth fillings, and poisons from infected teeth.
• Medicine--aspirin, tranquillizers, cough mixtures, antibiotics, vaccinations etc.
• All drugs used habitually whether taken intravenously, orally or inhaled, including marijuana, etc and antibiotics.
• Alcohol, smoking, overweight, and overwork,
• Fatigue, anger, pain, worry, frustration, grief, fear,
• Excessive athletic training and constant sexual promiscuity.

Dietary and nutritional factors

            For the immune system to be strong a low fat diet is essential. Foods that give a boost to the immune system should be included in diet. Food items including vitamin C rich foods like apples, oranges, broccoli, cantaloupe, brown rice and olive oil make the immune system stronger. Cartenoids such as carrots, yams, tomatoes, and pumpkins are high in antioxidants and fiber neutralizes the free radicals in our body. Shitake and Maitake mushrooms are found to have anti-aging, and immune boosting capabilities. Green leafy vegetables, whole grains, beans, fruit and roots help in making the immune system stronger.
            Include fish and poultry in everyday diet, as they have been found to be beneficial for the immune system. Do not consume too much dairy products. Even red meat and eggs should be taken in moderation.
Soybeans and soy products such as tofu and soy milk have many benefits like they helps in lowering cholesterol levels, reduces risk for cancer, and helps in preventing from osteoporosis, improves diabetes, lowers risk for heart disease

 Recommendations

• ‘Laughter is the best medicine’. This adage holds true in case of immune system too. Try to be happy and laugh as much as you can.
• Proper and sound sleep is very necessary for a healthy immune system. Make sure to have atleast 6-8 hours of sleep every day.
• Do exercise on a regular basis. Walk or jog, for at least 30 minutes, 4 times a week.
• Reduce your consumption of processed and packaged foods as much as possible. Instead, try to stick to fresh foods and vegetables.

• Consume organic food as much as possible.
• Herbal teas, like green tea and black tea, boost the immune system, since they contain antioxidants, bioflavonoid, tannins and indoles.
• Try to avoid the food items that contain polyunsaturated vegetable oils.

• Garlic is very good for the immune system of the body. Take it either raw or in cooked form.
• Herbal medicines like Echinacea which is available in the form of capsules and liquid extracts; this will improve immune system by increasing the production the antibodies and the activities of the white blood cells.
• Herbs like Siberian ginseng and the Indian ginseng are also used to improve immune system.
• A rainforest herb uña de gato found in Peru will improve immune system. It is also called cat’s claw due to its appearance like a claw.
• Junk food, high sugar, high salt, high fat, high cholesterol has a very bad effect on immune system.