What Does the "Immunological Body" Eat? Metchnikoff and Digestion as Warfare

Today we are accustomed to the idea that eating certain foods can help to support the immune system. Over the last two decades, this familiar narrative has been bolstered by the rise of microbial science and the growing popularity of biome-led nutrition, which encourages eaters to nourish the flora and fauna of their guts for the sake of better overall health. While our current preoccupation with the microbiome can be dated to the launch of the Human Microbiome Project in 2007, its origin story can be traced much further back. It begins with work undertaken by scientists and physicians around the turn of the 20th century aimed at understanding the significance of microbes in the digestive system. One of those, the Russian zoologist Élie Metchnikoff (1845-1916), is perhaps best remembered as the founder of modern immunology, and his work on phagocytosis-the capacity of certain specialized cells to engulf and eliminate intruders-earned him the Nobel Prize in 1908. According to Metchnikoff, the gut was the "engine of senility," where pathogenic bacteria multiplied and threatened to overwhelm the body's defenses. Transforming the belly into a battleground where good bacteria went to war with bad, Metchnikoff's influential work extended his theorization of organic immunity as a form of intercellular defense to the vexed question of what to eat and created the foundation for Emily Martin's "immunological body," an understanding of the body that likens it to a nation state, defined through the careful maintenance of the boundary between self and non-self, at this intersection of dietetics and immunology.