Why Daylight Boosts Immunity

Summary

Short Wave: Why Daylight Boosts Immunity
Podcast Episode Summary
Release Date: May 30, 2025

Short Wave by NPR delves into intriguing scientific topics with a blend of creativity and humor. In the episode titled "Why Daylight Boosts Immunity," hosts Regina Barber and Burleigh McCoy, alongside guest Ari Shapiro from All Things Considered, explore three captivating stories: the circadian rhythms of the immune system, innovative infrared-contact lenses, and the cunning hunting strategies of a Cooper's hawk in New Jersey.

---

1. Immune System's Circadian Clock

Overview:
The episode kicks off with an exploration of how our immune system operates differently depending on the time of day. Scientists have discovered that our bodies are better equipped to fend off infections during daylight hours.

Key Points:

• Day vs. Night Immune Responses:
  Burleigh McCoy explains, “...we're actually better at mounting preventing an immune response in the daytime” (02:19). This adaptation aligns with our evolutionary patterns of being more active during the day, increasing the likelihood of injuries or infections that the immune system must address.

• Neutrophils and Circadian Rhythms:
  Immunologist Jennifer Hurley discusses the role of neutrophils, crucial immune cells that "show up with all the energy, they try and kill off everything that they can, and then they book it out of here, and then they die" (02:59). Despite their short lifespan, neutrophils possess a built-in circadian clock that dictates their activity levels throughout the day.

• Research Using Zebrafish:
  To study these rhythms, researchers employed transparent baby zebrafish, allowing them to observe interactions between fluorescent bacteria and neutrophils. Immunologist Chris Hall notes, “...during the day, they killed the bacteria faster” (03:47). Disrupting the neutrophils' circadian clock impaired their ability to respond effectively.

Implications:
Understanding the immune system's timing opens avenues for enhancing disease treatment. For instance, scientists aim to "freeze neutrophils in the daytime state" to bolster immune responses during severe infections (04:22), or alternatively, adjust clock genes to reduce excessive inflammation (04:27).

---

2. Infrared-Seeing Contact Lenses

Overview:
The second story delves into cutting-edge contact lens technology that enables wearers to perceive infrared light, a feature reminiscent of high-tech gadgets seen in espionage films.

Key Points:

• Technology and Functionality:
  Regina Barber explains that these prototype lenses "embed tiny microscopic particles... to convert certain wavelengths of infrared light to specific wavelengths of visible light" (05:09). This conversion allows infrared light to be seen as different colors, expanding human vision beyond the visible spectrum.

• Current Limitations:
  Burleigh McCoy acknowledges, “...these prototype lenses aren't very sensitive. They can only pick up infrared light sources in the lab” (04:41). Additionally, the conversion process can result in blurred images, although pairing the lenses with specialized eyeglasses helps mitigate this issue by focusing the infrared light to clarify shapes and letters (05:24).

• Novel Discoveries:
  A remarkable feature is the ability to "see infrared light when their eyes were closed" (05:48). This occurs because infrared wavelengths can penetrate eyelids, offering unique observational capabilities even without direct eye contact.

Potential Applications:
While still in development, these lenses could revolutionize various fields:

• Enhanced Visibility in Low Light:
  Drivers could benefit from improved vision in foggy conditions where infrared light travels farther without scattering (06:08).

• Security and Communication:
  In crowded or high-security environments, individuals could communicate discreetly using infrared signals visible only to those wearing the lenses (06:29).

• Medical Imaging:
  Doctors might use infrared vision to detect the edges of tumors marked with infrared dyes, enhancing diagnostic accuracy (06:29).

---

3. The Tactical Cooper's Hawk

Overview:
The final story recounts the observation of a Cooper's hawk in New Jersey exhibiting strategic hunting behavior influenced by human traffic signals.

Key Points:

• Hawk's Hunting Strategy:
  Zoologist Vladimir Deniz describes a hawk waiting near a traffic light at a family's home known for attracting small birds with leftover crumbs. The hawk "would cross between two cars and grab a bird from that flock" (07:25), effectively using vehicular traffic as cover for its ambush.

• Anticipating Traffic Signals:
  Vladimir noticed that the hawk timed its attacks based on the beeping sound of the crosswalk button, which extended the red light duration. "It seemed to know in advance when the line of cars would become particularly long" (07:36), providing the hawk with the perfect moment to strike unnoticed.

• Expert Skepticism:
  Behavioral ecologist Petra Zumutzkutner expressed excitement but remained skeptical about attributing the hawk's behavior solely to the crosswalk sound, highlighting the need for more observations to confirm such intelligence in raptors (08:28).

Outcome:
The hawk's prey-attacking behavior ceased when the crosswalk button was silenced and crumbs were no longer available, leaving hopes that the hawk may have relocated or adapted its hunting methods (08:49).

---

Conclusion

In this episode of Short Wave, Regina Barber, Burleigh McCoy, and Ari Shapiro illuminate the intricate ways in which biology and technology intersect with daily life. From the immune system's internal clocks optimizing our defenses during the day, to revolutionary contact lenses expanding human perception, and the intelligent strategies of urban wildlife adapting to human patterns, the episode underscores the profound and often subtle interplay between natural processes and human innovation.

As Ari Shapiro aptly puts it near the end, "It's amazing" (05:59), reflecting the wonder and potential that these scientific discoveries hold for the future.

---

Produced by Jordan Marie Smith and Burleigh McCoy, edited by Rebecca Ramirez and Christopher Intagliata. Fact-checked by Tyler Jones with audio engineering by Jimmy Keeley and Tiffany Vera Castro.

Transcript

[Sponsor Announcement]

This message is from NPR sponsor Spectrum Business. From one employee to thousands, Spectrum delivers connectivity solutions at a great value for any size business. And it's all backed by the Spectrum commitment. Learn [e-mail] business.

[Regina Barber]

You're listening to Shortwave from NPR. Hey Shortwavers. Regina Barber here and Burleigh McCoy with our bi weekly science news roundup featuring the hosts of All Things Considered. And today we have one of our favorites, Ari Shapiro.

[Ari Shapiro]

Only one of your favorites. It's always an honor to be here.

[Regina Barber]

One of one of our five favorites.

[Ari Shapiro]

Well, let's get to the stories I hear today. We've got one on the immune system.

[Burleigh McCoy]

Telling time, contact lenses that allow you to see infrared light and a hawk.

[Regina Barber]

They may be using traffic to hunt for prey.

[Burleigh McCoy]

All that on this episode of Short Wave, the science podcast from npr, foreign.

[Edward Jones]

Support for NPR and the following message come from Edward Jones. What does it mean to live a rich life? It means brave first leaps, tearful goodbyes and everything in between. With over a hundred years of experience navigating the ups and downs of the market and of life, your Edward Jones financial advisor will be there to help you move ahead with confidence. Because with all you've done to find your rich, they'll do all they can to help you keep enjoying it.

[Sponsor Announcement]

EDWARD jones, Member, SIPC this message is from Spectrum Business. From independently owned storefronts just open for business to established professional services run from large offices, Spectrum is committed to delivering connectivity solutions for any size business. Create a plan made for your business with fast, reliable Internet, TV packages, phone, mobile services and more, all backed by the Spectrum commitment. From one employee to thousands, Spectrum keeps your business connected. Learn [e-mail] Business all right, Ari, where.

[Regina Barber]

Do you want to start?

[Ari Shapiro]

It sounds to me like your immune system may be in overdrive right now, Gina. So out of solidarity and sympathy, you want to tell us about the immune system telling time?

[Regina Barber]

Yes. I'm going to let Burleigh start though, but yes, that's sweet.

[Burleigh McCoy]

Yeah. So scientists have known that our immune responses are different depending on what time it is and that we're actually better at mounting preventing an immune response in the daytime. And this makes sense since we evolved to be more active in the day and so more likely to get an injury or infection. So by day the immune system is primed to fight potential invaders which it does by causing inflammation and at night it goes anti inflammatory to recover wild.

[Ari Shapiro]

How does the immune system know whether it's day or night time?

[Regina Barber]

Yeah, many immune cells have a built in circadian clock Like a lot of cells in our body, but there's some immune cells that don't even live a full day. Scientists wanted to know if they could tell time.

[Jennifer Hurley]

They're the frontline responders, right? They show up with all the energy, they try and kill off everything that they can, and then they book it out of here, and then they die.

[Burleigh McCoy]

This is immunologist Jennifer Hurley at Rensselaer Polytechnic Institute. She's talking about a special immune cell called a neutrophil that's really important at fighting off infections. And she says scientists hadn't really studied circadian rhythms in neutrophils because they die so fast.

[Jennifer Hurley]

Why even bother having a circadian rhythm in something that's not going to be very long lived?

[Ari Shapiro]

Fascinating question. How did scientists go about trying to answer it?

[Regina Barber]

Well, a different group of researchers used baby zebrafish, which are transparent, to watch how fluorescent bacteria interacted with fluorescent neutrophils. And they found that neutrophils can indeed tell whether it's day or night. We talked to immunologist Chris hall, who was part of that research team.

[Vladimir Deniz]

So during the day, they killed the bacteria faster, but if we removed components of the neutrophil circadian clock, that removed their ability to kill the bacteria faster because the neutrophils didn't know that it was daytime.

[Burleigh McCoy]

The team published their work in the journal Science Immunology.

[Ari Shapiro]

How could this knowledge be useful for people trying to fight diseases?

[Burleigh McCoy]

Yeah, so Chris says they're interested in seeing if they can freeze neutrophils in the daytime state. In the case, for example, you have a really bad infection and need all hands on deck.

[Regina Barber]

Or scientists could look at how to do the opposite. So, like, how to modify these clock immune genes to lower inflammation.

[Ari Shapiro]

Cool. Okay, next up, let's talk about these contact lenses that let the wearer see infrared light, which sounds to me like something out of James Bond or Mission Impossible. Are we talking about, like, night vision goggles in a contact lens?

[Burleigh McCoy]

Kind of, but with some big caveats. So right now, these prototype lenses aren't very sensitive. They can only pick up infrared light sources in the lab, so not out in the real world from a person or a car engine. But the lenses do have some advantages. They're less bulky than night vision goggles, and they can be worn in the daytime. And the big difference is that the contacts convert infrared into color vision instead of the mainly green or gray that night vision goggles do.

[Ari Shapiro]

How did scientists make them?

[Regina Barber]

Yeah, they embedded tiny microscopic particles in contact lenses. That convert certain wavelengths of infrared light to specific wavelengths of visible light. So using a few versions of these particles, they could convert a range of infrared light into different colors, but the.

[Burleigh McCoy]

Images they saw were blur. And that's because the direction the infrared light was originally traveling Gets lost when the contact lenses convert it to visible light. So that means making out the shape of the object also gets lost. So the researchers coupled the contact lenses with eyeglasses, and the eyeglasses were able to focus the infrared light In a way that participants can make out letters and shapes. And they described all this in the journal cell and ari.

[Regina Barber]

One really cool thing, it kind of blew my mind about these contact lenses, Is that participants could see infrared light when their eyes were closed. And this is because the long wavelength can actually go through eyelids.

[Ari Shapiro]

Wow, that's amazing. Now, it sounds like these might not be ready for prime time yet, but once they are on the market, what do you think people are going to do with them?

[Regina Barber]

Well, as we mentioned before, these won't pick up infrared in, like, the environment just yet. So scientists need to work on their efficiency, like turning infrared to visible light. But if they could do that, one advantage of wearing them Would be able to see when it's foggy or if there's low light. For example, if you're like driving across a bridge when it's foggy, Infrared light can travel farther, like, without scattering on fog particles.

[Burleigh McCoy]

You could also use this in, like, a security setting, so a concert or any other crowded place. If communication systems went down, security guards could communicate with each other quickly by shining infrared light that only they could see. Or doctors could use these to see edges of tumors that have infrared dyes.

[Ari Shapiro]

Wow. Okay, for the third story, you've got this hawk that I'm personally obsessed with. I've read all about this young Cooper's hawk in New Jersey set the scene for us.

[Burleigh McCoy]

Right? So there's a house in New Jersey near an intersection with a big front lawn. And. And sometimes the family that lives there eats outside, and that leads to crumbs. And the crumbs attract little birds that peck around at the leftovers. And those little birds attract this cooper's hawk, which preys on them.

[Regina Barber]

But if the hawk just swoops in, the prey will fly away. The hawk needs cover for this ambush. And that's when the story, like, really starts. Zoologist Vladimir Deniz observed a hawk waiting for a long string of cars to line up at this traffic light, and.

[Vladimir Deniz]

Then at the last moment, it would cross between two cars and grab A bird from that flock. But what was really interesting is that it seemed to know in advance when the line of cars would become particularly long.

[Ari Shapiro]

Yeah. So explain how this hawk knew in advance when the line of cars would become long.

[Regina Barber]

Yeah. So Vladimir noticed that whenever the crosswalk button was pushed, it would make this, like, beeping sound, and the hawk would position itself in a tree down the street from the crumb house, like, staging this attack. And he says that when the crosswalk button was, like, activated, the red light lasts a bit longer. And this would make the line of cars get, like, just long enough to give the hawk proper coverage for this, like, surprise attack.

[Burleigh McCoy]

So Vladimir spent a couple weeks watching this and saw the hawk attack six different times. And Vladimir's theory here is that the hawk just listens for the beeping sound to know when it can launch its attack. He wrote about it in the journal Frontiers in Ethology.

[Ari Shapiro]

So what's the takeaway here? Just, like, hawks are smart.

[Burleigh McCoy]

Well, so people who train raptors like hawks wouldn't be surprised by this behavior.

[Regina Barber]

Yeah. Still, it's important to keep in mind that this is, like, one hawk. This was only observed by Vladimir. It's not been filmed. So when we talk to Petra Zumutzkutner, a professor of behavioral ecology at the University of Vienna who didn't work on the study, she was excited about this behavior, but she was skeptical that this hawk was being cued by this crosswalk sound. She does. Welcome more observations.

[Burleigh McCoy]

Unfortunately, Vladimir says the crosswalk button no longer makes sounds and the family no longer leaves crumbs. So the hawk hasn't returned.

[Ari Shapiro]

Oh, that's such a sad ending. But I hope the hawk is living a fulfilling life wherever it is.

[Regina Barber]

We're all hoping for that. But, you know, we might not see the hawk again. But we're probably going to see you again. Ari, thank you for coming and hanging out with us.

[Ari Shapiro]

Thank you for having me. I always love this.

[Burleigh McCoy]

Come back anytime.

[Regina Barber]

You can hear more of Ari Shapiro on consider this NPR's afternoon podcast about what the news means for you.

[Burleigh McCoy]

Also, make sure you never miss an episode of our podcast, Short Wave by following us. It really helps the show out, just like sharing it with a friend.

[Regina Barber]

This episode was produced by Jordan Marie Smith and Burleigh McCoy. It was edited by Rebecca Ramirez and Christopher Intagliata.

[Burleigh McCoy]

Tyler Jones checked the facts. Jimmy Keeley and Tiffany Vera Castro were the audio engineers. I'm Burleigh McCoy.

[Regina Barber]

I'm Regina Barber. Thank you for listening to Short Wave, the science podcast from npr.

[Sponsor Announcement]

This message comes from Mint Mobile if you're tired of spending hundreds on big wireless bills, bogus fees and free perks, Mint Mobile might be right for you with plans starting from 15 bucks a month. Shop plans [e-mail] Switch upfront payment of $45 for 3 month 5 gigabyte plan required. New customer offer for first 3 months only, then full price plan options available, taxes and fees extra. See Mint Mobile for details.

[Edward Jones]

This message comes from U.S. bank. Simplify how you do business with Business Essentials, a powerful combination of no monthly maintenance fee, checking and card payment processing. Deposit products are offered by US Bank national association member fdic.

[Sponsor Announcement]

This message comes from Mint Mobile. Mint Mobile took what's wrong with wireless and made it right. They offer premium wireless plans for less and all plans include high speed data, unlimited talk and text and nationwide coverage. See for [e-mail] Switch.