Anyone who has had the good fortune to hear an orchestra brilliantly perform a symphony composed by one of the great masters knows that each of the carefully tuned musical instruments contributes to the collective, harmonious sound

produced by the musicians. In many ways, the normally tuned immune system continuously plays an orchestrated

symphony to maintain homeostasis.

The immune system is a “team effort,” involving many different players. These players can be divided roughly into two groups: those that are members of the innate immune system team and those that are part of the adaptive immune system. Importantly, these two groups work together to provide a powerful defense against invaders.

Immunology is a difficult subject for several reasons. First, there are lots of details, and sometimes these details get in

the way of understanding the concepts. To get around this problem, we’re going to concentrate on the big picture. It

will be easy for you to find the details somewhere else. Another difficulty in learning immunology is that there

is an exception to every rule. Immunologists love these exceptions, because they give clues as to how the immune

system functions. But for now, we’re just going to learn the rules. Oh sure, we’ll come upon exceptions from time

to time, but we won’t dwell on them. Our goal is to exam-ine the immune system, stripped to its essence.

A third difficulty in studying immunology is that our knowledge of the immune system is still evolving. As

you’ll see, there are many unanswered questions, and some of the things that seem true today will be proven

false tomorrow.

The term “immunology” is derived from Latin word “immunis” means exempt, i.e., protection from infectious diseases. Extensive work on bacteriology and pathology made their respective workers to find methods to develop resistance against infectious diseases in the latter half of 19th and beginning of 20th century. Although the history of immunology is about 100 years old, cellular immunology dates back to the 1950s

why is immunology so important? The immune system has involvement in almost all fields related to health and disease. Infections continue to confront human health and well-being on a global scale. Inflammation contributes to the

lung, heart and joint diseases, and diabetes mellitus; cancers have to evade immune surveillance, and immune dysregulation leads to allergies that are increasingly prevalent across the world. Only improved understanding of the

mechanisms by which microbes, allergens, and tumor cells cause disease will result in the development of diagnostic, therapeutic, and preventative strategies to combat this threat.However, we are only beginning the voyage of immunology, and there is much we still need to research and understand. The study of basic immunology may provide students with an opportunity to relate the findings of fundamental sciscientific investigations to clinical problems

history

Babylonian Epic of Gilgamesh (2000 B. C.) records the presence of pestilence and diseases. The study of Immunology stemmed out from the Thucydides’ description of individuals who recovered from the plague in Athens. Those individuals, who had already contracted the disease, recovered and became “immune.” Variolation was practiced for many years in China. The process involved exposing healthy people to the material derived from the lesions caused by the disease by either putting it under the skin or, more often, inserting powdered scabs from smallpox pustules into the nose. However, that occasionally resulted in death because there was no standardization of the inoculum. Variolation, later, became popular

in England, mainly due to the efforts of Lady Mary Wortley Montague and the American colonies. In 1796, Jenner inoculated James Phipps with the material obtained from a cowpox lesion, which appeared on the hand of a

dairymaid, and he inoculated the experimental subject with smallpox about six weeks later, without producing disease [1]. In 1875, Robert Koch was able to show the presence of anthrax causing bacteria in the lymph nodes of a dead rabbit that was earlier inoculated with the blood of a diseased animal [2]. In a serendipitous discovery, Pasteur was able to attenuate the virulent chicken cholera bacillus and coined the term vaccination. Later, he developed first viable vaccine for anthrax and rabies while Robert Koch studied hypersensitivity in tuberculosis. Although many consider Louis Pasteur the “father of

immunology,” it is due to his and Koch’s efforts that firmly established the historical germ theory of disease. Then, various scientists contributed to the development of the concept of cellular and humoral immunity. While working on the development of digestive organ in starfish larvae, Metchnikoff became a leading proponent of the “Cellularists.” He believed that phagocytes, not antibodies, played the leading role in immunity. Emil von Behring and Kitasato demonstrated the transfer of immunity against Diphtheria by a soluble “anti-toxin” in the blood whereby, Paul Ehrlich predicted the existence of immune bodies (antibodies) and side-chains from which they arise (receptors). Ehrlich suggested that antigens interact with receptors borne by cells, resulting in the secretion of excess receptors (antibodies).the supporters of alternative theory, i.e., “Humoralists,” believed that a soluble substance in the body was responsible for mediating immunity

OVERVIEW OF THE IMMUNE SYSTEM

PHYSICAL BARRIERS

immunological mechanisms

THE INNATE IMMUNE SYSTEM

THE ADAPTIVE IMMUNE SYSTEM

organ of immune system

cells of immune system

Antigen

Macrophage

what is immune response ?

immunoglobulin

immunotolerance

histocompatibility

immunotherapy

cytokines

complement system

Regulation of immune response

immunity to infection

transplantation immunology

autoimmune diseases

hypersensitivity

immunization

tumor immunology

immunodiagnostics