The antibody.

An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shape protein produced by plasma cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. It’s also circulating in the blood, scrutinizing every object that they touch. When they find an unfamiliar, foreign object, they bind tightly to its surface. By this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly, for example, by blocking a part of a microbe that is essential for its invasion and survival.

What compose of antibodies?

Antibodies are composed of four chains, such as, Two long heavy chains, that colored red and orange and two shorter light chains that yellow. The specific binding site that composed of several loops in the protein chain that have very different lengths and amino acid composition, is found at the tips of the two arms, in a pocket formed between the light and heavy chain.

The differences in these "hypervariable loops" form the many types of pockets in different antibodies, each of which bind specifically to a different target. The rest of the antibody--the rest of the arms and the large constant domain that ties the two arms together--is relatively uniform in structure, providing a convenient handle when antibodies interact with the rest of the immune system.

Antibodies are develops through encounters with a virus or bacterium that’s means, if you didn’t get sick or exposed to unhealthy elements, your body would be unable to develop antibodies that will serve as protection.
 
However, we can increase the number of our antibodies by several factors, such as, diet, fitness level and overall state of being.

How we can increase our antibodies?

• Eat foods high in the vitamins and minerals that benefit your immune system, including vitamin C, vitamin E, zinc, carotenoids and omega-3 fatty acids. All of these nutrients help your body in various ways to increase your antibodies and maintain these high levels.
• Exercise at least three or four times at least 20 or 30 minutes at a time, keeping the heart rate elevated the entire time. Exercise can also increase antibody production by up to 300 percent, and it also increases the presence of T-cells--aggressive cells that seek out, attack and kill unwanted viruses and bacteria.
• Maintain a happy, satisfying lifestyle. Being generally happy with our lives also tend to have more antibodies in our system. Happiness through the elimination of stress and anxiety, plus the integration of activities that encourage happiness, can boost antibodies by up to 50 percent.

A happy life can boost our immune system and give us a positive look.

Reference
http://www.rcsb.org/pdb/101/motm.do?momID=21
http://en.m.wikipedia.org/wiki/Antibody
http://www.livestrong.com/article/255696-how-to-raise-antibodies/#page=1