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Will you get sick next flu season? It may depend on how many natural killer cells you have

Scientists at Stanford find a biomarker for flu susceptibility, enabling predictions of if someone is going to fall ill to the virus after being exposed.

Let's imagine it's mid flu season, and a stranger at the grocery store sneezes on you.

Wouldn't it be great to know if you're destined for weeks of sweats and chills; or if, by the grace of your immune system, you might just make it out unscathed?

Purvesh Khatri, PhD, associate professor of medicine at Stanford, has discovered a biomarker in the blood may be able to do just that. It's a gene that codes for a protein that lives on the surface of a type of immune cell known as a "natural killer" cell. The findings of the study, published in Genome Medicine, have been in the works for about four years, and it's the first time (to Khatri's knowledge) that a biomarker for flu susceptibility has been identified.

Our release describes the biomarker:

[It's] a gene called KLRD1, and it essentially acts as a proxy for the presence of a special type of immune cell that may be a key to stamping out nascent flu infection. Put simply: the more of this cell type found in a person’s blood, the lower their flu susceptibility. The research even hints at new avenues for pursuing a broadly applicable flu vaccine.

Khatri pulled data from more than 150 different studies that analyzed the expression of various immune cell genes, keeping a careful eye out for patterns that could link a gene to protection against the flu. Then, Khatri took a closer look at data from two studies in particular, not conducted by his lab, that aimed to better understand how and why individuals got ill with the flu.

Using a computational approach developed in his lab, Khatri and his team parsed the identity and proportion of cells present in participants of two studies — one conducted at Harvard University, the other at Duke University — comprising a total of 52 individuals who volunteered to sniff up live influenza in the name of science. The researchers were looking only at types of immune cells present in each individual just before they were infected with the flu.


KLRD1, when expressed, manifests as a receptor on the surface of natural killer cells. KLRD1 is basically a counting chip. When the score was tallied, Khatri saw that, on the whole, those whose immune cells consisted of 10-13 percent natural killers did not succumb to the flu, whereas those whose natural killer cells fell short of 10 percent wound up ill. It’s a fine line, Khatri said, but the distinction between the groups is quite clear: Everyone who had 10 percent or more natural killer cells stood strong against the infection and showed no symptoms.

It's true, Khatri told me, the findings as they stand are only correlation, but the next steps are to figure out the mechanisms of protection and the overall role of natural killer cells in fending off the flu.

Photo by Kelly Sikkema

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