Immunology

IMMUNOLOGY

Historical Perspective And Scope Of Immunology

Progress in immunological science has been driven by the need to understand and exploit the generation of immune states exemplified now by the use of modern vaccines. From almost the first recorded observations, it was recognized that persons who had contracted and recovered from certain infectious diseases were not susceptible (i.e. were immune) to the effects of the same disease when re-exposed to the infection. Thucydides, over 2500 years ago, described in detail an epidemic in Athens (which could have been typhus or plague) and noted that sufferers were ‘touched by the pitying care of those who had recovered because they were themselves free of apprehension, for no one was ever attacked a second time or with a fatal result’.

Since that time many attempts have been made to induce this immune state. In ancient times the process of variolation (the inoculation of live organisms of smallpox obtained from the diseased pustules of patients who were recovering from the disease) was practised extensively in India and China. The success rate was very variable and often depended on the skill of the variolator. In the late 18th century Edward Jenner, an English country doctor, observed the similarity between the pustules of smallpox and those of cowpox, a disease that affected the udders of cows. He also observed that milkmaids who had contracted cowpox by the handling of diseased udders were immune to smallpox. Jenner deliberately inoculated a young boy with cowpox, and after the boy’s recovery, inoculated him again with the contents of a pustule taken from a patient suffering from smallpox; the boy did not succumb to infection from this first, or any subsequent challenges, with the smallpox virus. Even though the mechanisms by which this protected against smallpox were not understood, Jenner’ s work had shown proof of principle that the harmless stimulation of our adaptive immune system was capable of generating an immune state against a specific disease, and thereby provided the basis for the process we now understand as vaccination. The cowpox virus is otherwise known as the vaccinia virus and the term vaccine was introduced by Pasteur to commemorate Jenner’ s work.

In 1801 Jenner prophesied the eradication of small-pox by the practice of vaccination. In 1967 smallpox infected 10 million people worldwide. The World Health Organization (WHO) initiated a programme of confinement and vaccination with the aim of eradicating the disease. In Somalia in 1977 the last case of naturally acquired smallpox occurred, and in 1979 WHO announced the total eradication of smallpox, thus fulfilling Jenner’s prophecy. Many vaccine products are now available designed to provide protection against a range of infectious diseases. Their value has been proven in national vaccination programmes leading to dramatic reductions in morbidity and mortality of such diseases as diphtheria, pertussis, mumps, measles, rubella, and hepatitis A and B.

Further progress in the understanding of the complex nature and functioning of the immune system has been gained through the recognition that many varied forms of pathology, beyond that of infectious disease per se, have an underlying immunological basis, including such diseases as asthma, diabetes, rheumatoid arthritis and many forms of cancer. A basic knowledge of how the immune system functions is essential for health professionals involved in understanding the nature of disease and rationalizing therapeutic strategies. This chapter aims to provide a sound overview of the structure and functioning of the immune system and impart the reader with knowledge which will serve as a platform for the study of more complex specialized texts if and when required.