As you all know, I like to report on studies done in humans whenever possible, so here goes! Scientists at Memorial Sloan Kettering Cancer Center, In New York City, conducted really interesting research on patients who had received bone marrow transplants as part of their treatment for cancers like leukemia and lymphoma.[i] During treatment for these illnesses, chemotherapy and radiation are used to destroy the cancerous bone marrow – where many of our immune cells are produced – and then this is replaced with stem cells. Over time, the donated stem cells restore the bone marrow but while it is recovering, these patients need to take antibiotics to prevent infection, as they are hugely immunologically compromised and vulnerable. Once the bone marrow is restored, they can stop taking antibiotics, allowing their bacterial microbiomes to also recover. This set of unavoidable circumstances gave researchers the opportunity to watch, in incredible detail, how the microbiota affect the immune system.
On a daily basis, they tracked (via blood and stool samples) the changes in the microbiota and the number of immune cells in the blood of more than 2000 patients. They also collected information about the patients’ medications as well as side effects. This resulted in, as you can imagine, thousands of data points, allowing them to spot patterns in the data. Said one of the senior researchers, “The parallel recoveries of the immune system and the microbiota, both of which are damaged and then restored, gives us a unique opportunity to analyze the associations between these two systems…”[ii]
The results may end up being incredibly useful in helping patients recover more quickly. They found that Faecalibacterium, Ruminococcus, and Akkermansia were associated with increased levels of neutrophils, a kind of immune cell, in the blood. Other bacteria (Rothia and Clostridium sensu stricto) were associated with reduced neutrophil levels. Thus, the hope is that further research provides a means of more rapidly recolonizing, via a customized probiotic, the damaged guts of these patients: “Simulations predict that microbiota enriched in these genera accelerate immune reconstitution, and reduce the time until neutrophils reach a [normal] level…”
Of course this research is not only relevant to those who’ve had bone marrow transplants. The fact that they were able to clearly isolate species that specifically boost immune levels and normalize functioning may well be highly significant in countless diseases. Their concluding sentence: “Our demonstration that the microbiota influences systemic immunity in humans opens the door towards an exploration of potential microbiota-targeted interventions to improve immunotherapy and treatments for immune-mediated and inflammatory diseases.”
Amen to that, right?!
[i] Schluter, J., Peled, J.U., Taylor, B.P. et al. The gut microbiota is associated with immune cell dynamics in humans. Nature (2020). https://doi.org/10.1038/s41586-020-2971-8