Luba Vikhanski’s graceful biography of Elie Metchnikoff is the first English study published in twenty-five years. Through extensive archival research she has [End Page 140] provided the most intimate portrait available of this remarkable scientist, and in celebration of the centennial of his death, it is a timely account. In 1911, a public poll ranked him among the world’s ten greatest men. Not to gainsay “greatest,” clearly he was an international celebrity for at least two well-publicized contributions. The first, and the one firmly grounded in his research, concerned the discernment of how animals combatted microbial pathogens. He argued that phagocytes composed the first line of immune defense, while his German competitors maintained that immunity rested with the passive action of antitoxins. The debate became polemical, not only on the basis of scientific arguments, but it also included prideful nationalism, where Metchnikoff’s French supporters paired off against the German representatives of the chemical school. The argument finally abated after twenty years of controversy with the 1908 Noble Prize jointly awarded to Metchnikoff and Paul Ehrlich, the key champion of chemical immunity.
Metchnikoff’s second major claim to fame, a theory about prolonging human life span, arose as a corollary of his “phagocyte theory.” He believed that bacterial toxins secreted from resident microbes in the bowel were important contributors to aging and maintained that reparative mechanisms were insufficient for ensuring vitality. He prescribed yogurt, rich in lactobacillus, to replace deleterious resident bacteria and thereby eliminate their toxins. His idea took the health-conscious public by storm. Through his advocacy, yogurt became popular in France (he took no financial benefit for his efforts) and, more generally, the translation of bench science for public welfare was greeted enthusiastically. Not only had antitoxin serum therapy recently proved an effective treatment against diphtheria, an application of immunological principles would putatively prolong life as well.
Both contributions may be viewed as early applications of ecological ideas to the clinic; however, few understood the basis or implications of Metchnikoff’s thought. And here the story assumes both historical and philosophical complexity. Metchnikoff creatively engaged Darwinism, both in the particular investigative problems he addressed, but more basically as the source of his theories. For him, phagocytes were agents attending to any state of “disharmony”—whether infectious or injurious. That part of the theory is always highlighted and closely follows the host-defense version of immunology’s history. But these adult processes originated in a developmental context: He inserted Darwinian struggle between species into the developing animal body and regarded the phagocyte as mediating the competition between cell lines, each of which promoted their own self-aggrandizement. So when he added the expected consequences of aging to the spectrum of immunity, that is, addressing the ordinary “disharmonious” state arising from the appearance of effete and malignant cells, “physiological inflammation” became a general normalization process for seeking “harmony,” or balance.
The fertility of Metchnikoff’s broad phylogenetic survey of phagocyte functions yielded a common, primordial conceptual denominator: Immunity was those processes that established the boundaries of animal identity by mediating a balanced ecology (ergo, immune defense, and yogurt). With prescient insight he assigned immunity the function of gatekeeper (to reject or assimilate) the animal’s ever-changing challenges and opportunities in a complex exterior and inner [End Page 141] ecology. Identity then becomes a problem, for environmental context, contingency (epigenetic effects), and history (immune memory) aggregate to determine the immune response and the resultant contours of individuality.
Today, despite a century of dormancy, Metchnikoff’s ecological-developmental synthesis has reappeared in the study of ubiquitous symbiosis that has redefined organismal individuality in terms of development, physiology, immunity, and evolution. In a collective consortium, immunity regulates the balance of species that permits mutualistic benefit or effects elimination. So to claim that Metchnikoff “changed the course of modern medicine” must be understood not only in terms of the immediate impact of his theory of cell-mediated immunity, but also in regard to the long-term influence of his broader hypothesis concerning how the animal copes with its ecological demands. This latter aspect of his thinking has reemerged as a major theme of contemporary biology and historians should take note of its genesis.