Innate immunity and microbiota

Although Elie Metchnikoff studied the link between the good health, diet and flora of certain populations (see The Microbiota Chronicle p .15), immunity, or the idea of immunity, was deeply marked by Pasteur's vision; microbes are considered to be "harmful" and the main purpose of immunity is to eliminate them.

Since the 1950s, research efforts have focused particularly on adaptive immunity, ultimately presented as the final stage of the evolution of the immune system. During this period, when the microbe was the enemy and theories drawn from Pasteur were applied at a clinical level, infectious diseases saw significant regression, a commendable outcome. But paradoxically, the incidence of immune disorders such as inflammatory diseases, allergies, diabetes and other autoimmune diseases has exploded.

It was in the 1980s that the hygiene hypothesis advanced the link between immune disorders and the microbiota. But it was the progress of analytical tools, the discovery of innate immunity receptors (PRR) capable of recognizing the conserved patterns of microbes, and the use of germ free mouse models that demonstrated the major role of the microbiota in the development and control of immunity and its ability to adapt to the environment. Our view of immunity has therefore evolved into one of a system whose goal is to seek balance between an external and internal environment, and in which the microbiota is a primary interface for communication, exchange, regulation and, consequently, balance. The view of adaptive immunity has also evolved from a system “supplanting” innate immunity to a system that is in fact an “effector” of innate immune response. The special report that we present today illustrates the essential role of the microbiota and innate immunity in immune homeostasis and the interview with Dr. Jehane Fadlallah, whom I thank, completes this feature by focusing more specifically on adaptive immunity.

I hope you enjoy reading it.

Cyrille Hoarau
Editor in chief of this issue