Just Seeing Another Sick Bird Can Jump-start a Bird’s Immune System

That 2010 research study, Love informed me, “sort of blew my mind,” due to the fact that it didn’t follow the common trajectory of the body immune system responding to a continuous attack. Rather, the cells were internalizing visual hints and strengthening themselves preemptively—raising guards versus an attack that hadn’t yet taken place, and possibly never ever would. It was what you may call spectator resistance, and it was absolutely unusual.

Love chose to attempt her own variation in domestic canaries, amongst the numerous bird types prone to a pathogen called Mycoplasma gallisepticum. She contaminated 10 canaries with Mycoplasma, then put them in sight of microbe-free birds. In parallel, she had 2 other cadres of healthy canaries scope each other out, as a symptomless point of contrast.

Throughout the 24-day experiment, the uninfected canaries served as a lot of songbirds do, feeding, chirping, and bopping cheerily around their cages. However about a week in, the birds dosed with Mycoplasma ended up being mopey and sluggish, and established a nasty kind of pink eye. “I could approach the cage and just pick them up,” Love informed me. (Some Mycoplasma types can trigger illness in people; this one doesn’t.)

The birds viewing their beleaguered peers never ever got contaminated themselves. However when Love and her associates analyzed the canaries’ blood, they discovered that a few of the birds’ immune actions had actually swelled in near lockstep with the ill birds’ signs. Cells called heterophils—inflammation-promoting foot soldiers that fight on the front lines of many avian infections—had flooded the bloodstream, similar to how they would in the presence of Mycoplasma, Love said. The birds’ blood was also rife with so-called complement molecules, which can shred bacterial cells, or flag them for other types of destruction.

The uptick was temporary. As the symptoms of the sickened birds abated, their observers’ immune cells quieted down as well. Love told me she suspects that these little flare-ups might have primed the watchful birds for a possible tussle with the pathogen—perhaps cloaking them in a light layer of armor, akin to a very crude and very ephemeral vaccine.

To confirm that idea, Love would have needed to expose the onlooker birds to Mycoplasma while their immune systems were still raring to go, an experiment she is working on now. Without those data, “it’s hard to know what this means,” Jesyka Meléndez Rosa, an immunologist at Humboldt State University who wasn’t involved in the study, told me.

The immunological surge did seem driven by the disease cues that the other birds emitted, because samples taken from the canaries who’d peeped on only healthy birds stayed comparatively inert. But what the researchers discovered could have just been a blip—noticeable, yet not strong enough to alter the trajectory of a subsequent infection. A bystander immune response could even be a net negative for the witness, wasting precious bodily resources or unnecessarily damaging healthy tissues. Heterophils and complement molecules also comprise just a small subset of the immune system’s arsenal, much more of which would be marshaled into quelling a Mycoplasma invasion. Letícia Soares, a disease ecologist at Western University who wasn’t involved in the study, told me she wished she’d been able to see how well the observer birds’ immune actions mimic what occurs in contaminated birds who ultimately recuperate.

Jobber Wiki author Frank Long contributed to this report.