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Introduction to Immunology-Part I

© David Olle

For more than a century, researchers have been intrigued with the idea of treating cancer by means of activating the immune system of the body. The appeal of the method is due to its specificity. When bacteria or virus invade the body, the immune system mounts a very specialized attack on the invader. Research efforts revolve around the thought that if the immune system could be activated against a particular cancer, it could specifically hone in and destroy the cancer cells without harming normal cells. This would be in sharp contrast to current methods of surgery, chemotherapy and radiation which have well-known adverse side effects. Another problem with these methods is that the cancer often recurs after treatment. In order to overcome this problem, immunotherapy could be applied to seek out and destroy those cancer cells that have escaped and have avoided detection. Unfortunately, attempts to develop immunotherapy have a long history of failure. The medical community now has a much better understanding of immunology and the nature of cancer and can identify reasons for previous failures. There are now many promising approaches to treatment under development, but before I discuss them, I will provide a brief two-part introduction to immunology.

Overview

Immunology is the study of the process by which the body develops resistance to invading organisms. This process is known as the immune response and has two primary characteristics. The first characteristic is specificity, in which the immune system can identify a unique feature of a cell or organism and develop the means to react only to that organism. The second characteristic is memory, which is the ability to remember previous encounters and to respond more rapidly and vigorously on second exposure. The immune response depends upon the identification of an antigen. Antigens are proteins and polysaccharides that are found on the surface of bacteria, viruses, body cells and foreign substances such as wood slivers that may enter the body. In my articles, the term antigens could refer to any of these substances. All body cells have the potential to be antigenic, since the surface protein molecules are unique to each person. It is the responsibility of the immune system to learn to distinguish between cells that are natural to the body (or "self") from cells or substances foreign to the body (or "non-self"). The immune system fails in this distinction in the case of cancer cells when it recognizes the cancer cells as "self" and does not attack them. The immune system also demonstrates aberrant behavior in the case of autoimmune diseases such as lupus and juvenile diabetes when it attacks normal cells as foreign. To accomplish its tasks, the immune system has developed a very complex system of communication between its components and the means of responding to this communication with appropriate checks and balances.