The old friends hypothesis - Philosophical Concept | Alexandria
The old friends hypothesis, an immunological concept, proposes that our immune systems evolved in a symbiotic relationship with a diverse array of microorganisms, particularly those encountered in early childhood. Its essence lies in the idea that these "old friends," including commensal bacteria, helminths, and environmental microbes, are crucial for the proper education and regulation of our immune responses. Could our obsessive cleanliness be a form of self-sabotage, inadvertently disconnecting us from allies essential to our well-being?
While not explicitly termed as such, the genesis of the old friends hypothesis can be traced to observations made in the late 20th century. Epidemiological studies in the 1980s and 1990s revealed an inverse correlation between exposure to certain infections in childhood and the subsequent development of allergic and autoimmune diseases. This was a period of rising awareness of environmental impacts on health, coinciding with increased hygiene standards and the widespread use of antibiotics. Were we inadvertently disrupting ancient partnerships forged over millennia?
The hypothesis gained significant traction in the early 2000s, championed by immunologists like Graham Rook. Central to its evolution was the understanding that the immune system, rather than solely focusing on eradication, requires chronic but controlled stimulation from these "old friends" to develop tolerance and suppress aberrant inflammatory responses. Research continues to uncover specific mechanisms involving regulatory T cells and innate immune pathways. Intriguingly, some studies suggest that exposure to helminths – parasitic worms – can alleviate symptoms of autoimmune disorders, leading to experimental therapies that challenge conventional medical wisdom.
The legacy of the old friends hypothesis extends beyond the laboratory, influencing public health strategies and sparking a renewed interest in the human microbiome. It prompts us to reconsider our relationship with the microbial world, questioning the wisdom of blanket eradication efforts and encouraging a more nuanced understanding of microbial ecology. As we grapple with the escalating burden of immune-mediated diseases, the old friends hypothesis serves as a reminder that our health is inextricably linked to the invisible world around us, a world we are only beginning to understand. Are we facing an immunological identity crisis caused by a departure from an environment in which we evolved?