Prologue: The Term “Immunity” over the Course of Time

Abstract

In the Prologue of Part I, the long way of the term “immunity” is briefly sketched, ranging from its first registered use in the context of health and disease 2000 years ago up to the description of the self/nonself discrimination theory in immunology in the mid-1990s. Originally, the term was mainly employed by non-physicians and understood as a passive exemption from diseases provoked by gods or demons. After the introduction of “variolation” and Jenner’s “inoculation” of cowpox in Europe in the eighteenth century, the term began to be widely used by physicians. Soon after, the germ theory of disease and the first immune mechanisms of defense were launched which promoted the use of the term. “Immunity” was now understood as a protective battle against the germs. At that time, however, at the late 1800s, two competing immunological theories were born: the “cellular theory” proposed by Metchnikoff in Russia holding that phagocytes play the dominant role in immune defense and the “humoral theory” proposed by Paul Ehrlich and Emil von Behring in Germany holding that a soluble substance in the body was mainly responsible for mediating immunity. Today it is known: both the “cellularists” and the “humoralists” were correct.