Management Aptitude Test 2016 Paper

Passage‌IV
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune system in defending the body relies on a dynamic regulatory communications network consisting of millions and millions of cells. Organised into sets and subsets, these cells pass information back and forth like clouds of bees swarming around a hive. The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate, effective and self-limiting. At the heart of the immune system is the ability to distinguish between self and non-self. When immune defenders encounter cells or organisms carrying foreign or non-self-molecules, the immune troops move quickly to eliminate the intruders.
Virtually every body cell carries distinctive molecules that identify it as self. The body’s immune defences do not normally attack tissues that carry a self-marker. Rather, immune cells and other body cells coexist peaceably in a state known as self-tolerance. When a normally functioning immune system attacks a non-self-molecule, the system has the ability to remember the specifics of the foreign body. Upon subsequent encounters with the same species of molecules, the immune system reacts accordingly. With the possible exception of antibodies passed during lactation, this so-called immune system memory is not inherited. Despite the occurrence of a virus in your family, your immune system must learn from experience with the many millions of distinctive non-self-molecules in the sea of microbes in which we live. Learning entails producing the appropriate molecules and cells to match up with and counteract each non-self-invader. Any substance capable of triggering an immune response is called an antigen.
Antigens are not to be confused with allergens, which are most often harmless substances (such as ragweed pollen or cat hair) that provoke the immune system to set off the inappropriate and harmful response known as allergy. Ad antigen can be a virus, a bacterium, a fungus, a parasite, or even a portion or product of one of these organisms Tissues or cells from another individual (except an identical twin, whose cells carry identical self-markers) also act as antigens; because the immune system recognises transplanted tissues as foreign, it rejects them. The body will even reject nourishing proteins unless they are first broken down by the digestive system into their primary, non-antigenic building blocks. An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes. which protrude from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitope on their surface; some may even carry several hundred. Some epitopes will be more effective than others stimulating an immune response . only in abnormal situations does the immune system wrongly identify self and non self and execute a misdirected immune attack. The result can be a so called automotive diseases such as rheumatoid arthritis or systematic lupus erythematosis. The painful side effects of these diseases are caused by a person's immune system actually attacking itself.