[RADIOLAB INTRO]

JAD ABUMRAD: Hey, I'm Jad Abumrad.

ROBERT KRULWICH: I'm Robert Krulwich.

JAD: This is Radiolab.

ROBERT: The podcast.

JAD: And before we really get rolling, I just want to say one thing: we're gonna be in LA next week, May 8, 9 and 10. We're gonna be at the Royce Theater for three nights with our live show, In the Dark, which includes Pilobolus, the dance troupe, the singer-songwriter Thao Nguyen, and the comedian Demetri Martin. Awesome lineup. You can still get tickets at Radiolab.org/inthedark. Folks who've seen this show, tell your LA peeps to come check it out.

ROBERT: Yeah.

JAD: I don't know what we're doing today, so you go.

ROBERT: Well, because here's what we're doing: maybe six years ago, I'd just returned to National Public Radio, and for the first story I did ...

JAD: Can we just put that in context? I mean, you started National Public Radio.

ROBERT: [laughs] I didn't start it.

JAD: You did kind of start it.

ROBERT: I was at it near the beginning.

JAD: And then you went away to do great things on TV.

ROBERT: For 23 years I was missing.

JAD: And then you came back.

ROBERT: Then I just popped back again, yes.

JAD: Okay.

ROBERT: When I popped back, I brought this puzzle back with me. It was about motherhood, actually. And it's—we'll you'll hear. Why don't I just play you the piece that I aired back in—gosh ...

PRODUCER: 2006.

ROBERT: 2006?

JAD: That's another time.

RADIO HOST: NPR's Robert Krulwich has the story.

ROBERT: For years, it was thought as soon as a baby is conceived, once it starts to grow inside a mom, it gets its own very private space.

KIRBY JOHNSON: There is. There's a placenta. A placenta was thought to be a fairly impenetrable barrier.

ROBERT: So, says Dr. Kirby Johnson of Tufts University, the baby and its cells stay on the baby's side. The mommy's cells stay on the mommy side, and nature keeps them separate until it's time to go. But here's the surprise: when scientists at Tufts took blood from ordinary pregnant moms ...

KIRBY JOHNSON: We would find, for example, in a teaspoon of blood, dozens, perhaps even hundreds of cells.

ROBERT: From the baby.

KIRBY JOHNSON: From the baby.

ROBERT: So baby cells were slipping out of the placenta into the moms. But because babies do have different genes ...

KIRBY JOHNSON: One would expect them to be attacked fairly rapidly. You would expect them to be cleared within hours if not days. What we've found is that that is not the case, not anywhere near the case.

ROBERT: It turns out that baby cells stay in their moms not for days or weeks, but for decades.

KIRBY JOHNSON: Four to five decades following the last pregnancy.

ROBERT: So 40 years after conception, that son or daughter who can now be a middle-aged pharmacist or something, yet their fetal cells, their baby cells are still floating around inside the mother?

KIRBY JOHNSON: Yes.

ROBERT: Even his 60-year-old mother? 70?

KIRBY JOHNSON: 70, 80, perhaps 90-year-old women.

ROBERT: You're sure of this?

KIRBY JOHNSON: Absolutely.

CAROL ARTLETT: Yeah, these cells last essentially forever.

ROBERT: In the mom?

CAROL ARTLETT: In the mom.

ROBERT: And, says Carol Artlett who studies fetal cells at Thomas Jefferson University in Philadelphia, even if a woman has a miscarriage or an abortion, even if there is no baby, the cells of an unborn child will stay in the mother for decades. But why? What exactly are they doing in there for years and years and years?

CAROL ARTLETT: That's a good question.

ROBERT: [laughs]

ROBERT: Well, one early hypothesis, and it's not the nicest idea, says Kirby Johnson, is that certain autoimmune diseases ...

KIRBY JOHNSON: Such as lupus, rheumatoid arthritis, scleroderma are much more common in women than men. And that's one component of the hypothesis is that this prevalence in women is due to fetal cells.

ROBERT: So later in life, when the mother's joints inflame, maybe it's her fetal cells, her own babies taking a poke at her. In fact, Kirby's mom did have an autoimmune disease. It was a bad one, and for a while Kirby thought well, his cells were responsible.

KIRBY JOHNSON: So I apologized immediately and said, "Well, there's nothing much I can do about it."

ROBERT: Yeah, yeah. But it's like, "Stop it, Kirby!"

KIRBY JOHNSON: But you know what? I was always doing that to my mother. Always causing problems, and it was just another on the long line of those kinds of things.

ROBERT: But happily, the folks at Tufts proposed an alternative, a second theory to explain what fetal cells are doing in the moms.

KIRBY JOHNSON: Well, theory number two is the polar opposite of theory number one.

ROBERT: The "good" fetal cell hypothesis proposes that the son or daughter's cells stay in mom not to hurt her, but to protect, defend and repair her for the rest of her life, whenever she gets seriously ill. And that's a more attractive idea.

KIRBY JOHNSON: It's such a personal thing, and it does touch the heartstrings of even the most hard-nosed research scientist.

ROBERT: But they all have mothers.

KIRBY JOHNSON: But they all have mothers.

ROBERT: And happily, they now have evidence. More and more evidence, says Kirby Johnson, that looks like the good hypothesis may be correct. For example, here's a case ...

KIRBY JOHNSON: Well, this was a woman who came into a neighboring hospital in Boston with symptoms of hepatitis. She was an intravenous drug user.

ROBERT: And she had had five conceptions. She'd had one child, two miscarriages, two abortions—that's five in all. She could be carrying, therefore, a lot of fetal cells. And they examined her.

KIRBY JOHNSON: And in the process, she had a liver biopsy.

ROBERT: And the doc said, "Well, why don't we send her liver to the lab to see if there are any fetal cells gathering where she's got trouble?" And when they looked ...

KIRBY JOHNSON: We found hundreds and hundreds of fetal cells.

ROBERT: Normally, they'd expect five or ten cells.

KIRBY JOHNSON: But this was a very large—we saw literally sheets of cells, whole areas that seemed to be normal.

ROBERT: Meaning that those fetal cells had gathered at the liver, and like stem cells, they just turned themselves, in this case, into healthy liver cells.

KIRBY JOHNSON: And most interestingly, this woman did not desire to have any further treatment done. In fact, she wanted to get back to her normal life and be left alone.

ROBERT: And she left the hospital with hepatitis, but when they checked months later, they learned ...

KIRBY JOHNSON: That she is completely healthy. No signs of further liver damage.

ROBERT: So no medical intervention, but just a huge number of her baby's fetal cells. Could that lead you to think the poetic thought that she was saved by her kids?

KIRBY JOHNSON: We want to think that.

ROBERT: I know you do. [laughs]

KIRBY JOHNSON: There—it's the most likely explanation.

ROBERT: But in science, there is such a thing as a too-dangerously beautiful idea.

KIRBY JOHNSON: That's right. Right. And we say the same thing to ourselves because it shows such a basic wonderful thing, but it has to be right, and we can't be led astray by our own desire for it to be true.

ROBERT: So they are systematically testing the good hypothesis and the bad hypothesis, all these ideas, on laboratory mice. And when they see mother mice with all kinds of diseases: infectious disease, cancer ...

KIRBY JOHNSON: Ovarian cancer, endometrial cancer, cervical cancers, we find fetal cells there. We know that fetal cells don't ...

ROBERT: Over and over and over and over.

KIRBY JOHNSON: Over and over and over and over.

ROBERT: Suggesting that fetal cells regularly rush to the places where they're needed in the mom, and says Carol Artlett ...

CAROL ARTLETT: There's a lot of evidence now starting to come out that these cells may actually be repairing tissue.

ROBERT: That is, protecting the mom. While the other hypothesis, that fetal cells hurt the moms, there, the more they look the less they find.

KIRBY JOHNSON: I can't recall a single study that's been truly reproduced to verify the bad fetal cell hypothesis.

ROBERT: So while no one knows in the end which way it'll go ...

KIRBY JOHNSON: I think that that's something that we're going to see within the next five years or less.

ROBERT: So far, a sense is building that fetal cells probably stay in mothers for decades to defend and to protect them, which increasingly is a quiet consolation to Kirby Johnson because it's now more likely that his cells and his brother's cells were helping their mom, not hurting. And even though his mother did die, Kirby's beginning to feel differently.

KIRBY JOHNSON: Well, maybe if it wasn't for my brother and I, she may have passed a few years earlier. Maybe we bought her a couple of extra years of time so she could have a few more birthdays and a few more Mother's Days. And that, if I can just say that, that there's some way where I can even have the remotest thought that I contributed to the extension of my mother's life, even if it was a few days, that would make all of the years that I've spent doing this research worthwhile.

ROBERT: Robert Krulwich, NPR News, New York.

JAD: Hmm.

ROBERT: So it's been more than five years, as I said, since I talked to Kirby Johnson, six years, really. So I figured he might have an answer by now.

KIRBY JOHNSON: Hello?"

ROBERT: Hi, Kirby.

KIRBY JOHNSON: Hi, Robert. How are you?

ROBERT: I wanted to know, what do you now know about what those fetal cells are really doing?

KIRBY JOHNSON: Right.

ROBERT: So when we last left it, you were tipping between two possibilities: one is that they do some harm, that they aggravate conditions later in the mother's life, or the opposite, that they help in the mother's life.

KIRBY JOHNSON: Right.

ROBERT: And do you now have a sense of which was right?

KIRBY JOHNSON: Well, I think it's more complicated than we originally thought. Like, you would expect ...

ROBERT: Isn't that always the case? [laughs]

JAD: Yes.

KIRBY JOHNSON: But what we're able to do though now, is more specifically argue for or argue against one of those different hypotheses. For example ...

ROBERT: So here's how he's addressed the question—because this is a completely new development. He's working with mice, and he's taken the glow from another animal.

KIRBY JOHNSON: ... comes from some sort of fish.

ROBERT: A greenish glow ...

KIRBY JOHNSON: The green fluorescent protein.

ROBERT: ... that exists in nature. He's plucked it onto the fetal cells of a pregnant mouse.

KIRBY JOHNSON: Right. Exactly.

ROBERT: So what is that like? Is that if you do a tummy scan on a pregnant lady mouse, can you look inside, and is that like going to the movies and see a little ...?

KIRBY JOHNSON: Absolutely. It is like the movies. It is shiny, glowing green, and it's extremely easy to see. I mean, a child could say that, "Oh, that's green."

ROBERT: So he can look at the mouse, and he can see from the little bits of green glow where the fetal cells are.

KIRBY JOHNSON: And we find these cells virtually anywhere we look, like the lung, the spleen, liver, bone marrow, the heart. We even find them in brain tissue.

ROBERT: Which will help figure out what they're doing.

JAD: So he can track them.

ROBERT: Yeah.

KIRBY JOHNSON: Yes.

ROBERT: Here I am!

KIRBY JOHNSON: And we've removed ...

ROBERT: And now that he has tracked them, he says, "All right, what I said before about fetal cells probably helping moms, I think that in many cases is still true. If you've got a mom who's suffering, say, from some liver disease or something, you can see fetal cells doing something there."

KIRBY JOHNSON: And these cells may be able to contribute to tissue repair after an injury or chemical or environmental assault. So these are helpers.

ROBERT: Helpers.

KIRBY JOHNSON: Definitely, yeah. But ...

ROBERT: But unlike six years ago, now he suspects that if a mother has, let's say rheumatoid arthritis or some kind of autoimmune disease ...

KIRBY JOHNSON: Where the maternal immune system seemingly attacks itself in this autoimmune fashion.

ROBERT: ... now he sees other kinds of fetal cells, that ...

KIRBY JOHNSON: Seem to be causing a problem.

ROBERT: Their behavior seems to suggest that they are attacking the mom.

KIRBY JOHNSON: Actually attacking maternal tissue.

ROBERT: So that's the go-get-Mommy group.

KIRBY JOHNSON: Right. And the unfortunate go-get-Mommy group.

JAD: Wait, so there are some kinds of fetal cells that are good, some that are bad, and it seems to depend on what again? On, like, where it is in the body or what disease?

ROBERT: Well, it seems to depend on a longer and longer list of variables, so including, for example, who the father was. That turns out to be ...

JAD: Why does that matter?

ROBERT: Well remember, every fetal cell is half mom and half dad.

KIRBY JOHNSON: We actually do see differences in the cells that are present in the mother, depending upon the genetic background of the father.

ROBERT: Oh, so you can have bad daddies and good daddies?

KIRBY JOHNSON: That is entirely possible. I think we would say good daddies and less-good daddies. But what we're finding ...

ROBERT: [laughs] Is that because you're at a university, and you never like to call daddies bad?

KIRBY JOHNSON: Yes. No one's a bad daddy.

JAD: But wait a second. Does he know how to explain the difference? Like, why one dad would be good and one wouldn't be good?

ROBERT: I don't think he knows yet. No.

KIRBY JOHNSON: We haven't been able to quite delineate why one cell may be doing something good or maybe be doing something bad. It may be the very same cell type.

ROBERT: Ooh, so it might even switch sides during the course of life?

KIRBY JOHNSON: It possibly could. I mean, it's sort of like behavior. You got good kids and you got bad kids.

ROBERT: [laughs] You got good days, you got bad days.

KIRBY JOHNSON: Bad days. You got good cells and you got bad cells.

JAD: This is getting complicated. So the cells can be good or bad, depends on the disease, the location, and the dad, but we're not really sure what.

ROBERT: And that's not the end of the list. It actually gets longer.

KIRBY JOHNSON: There's a number of other variables. The number of pregnancies, also pregnancy loss—whether it's through miscarriage or through termination. Maternal age. That's another very important variable.

ROBERT: So who's your daddy? How old are you when you're pregnant? How many times have you been pregnant before?

KIRBY JOHNSON: Yes. And many other influences. It's impossible to quant ...

ROBERT: Well, wait a second. So this—so when we got to the poetry part of our interview back then, you said to yourself, "My brother and I either roughed up our mother or gave her a few more, you know, birthdays."

KIRBY JOHNSON: Right. It's possible that one of us had a more positive impact than the other. I mean, there's obviously no way of knowing that, but any normally inquisitive mind would start to wander to say, "Well, what if this or under what circumstances ..."

ROBERT: Well see, my mind is wandering wildly now because when we last did this story ...

KIRBY JOHNSON: Yeah. And that's what we want you to do. We want people in our ...

ROBERT: No, I don't want to. It'll be a much better story if it was—if it had been—for me, if it had been—if it had gone clearly one way or the other. But the story you're now telling me is that you and your brother can now meet for coffee, and you can look into each other's eyes, and you will not know between the two of you, whether you helped your mom, whether you hurt your mom, whether you did both, whether your contribution was bigger or less than the happenstance of your dad's genetic makeup, and and and and—this is getting to be a much harder story to tell.

KIRBY JOHNSON: It is much harder to tell.

ROBERT: SO as the story gets blurrier and blurrier, why are you still in the game?

KIRBY JOHNSON: A lot of this is driven, as you know, by the issues that my mother has or had. And I still have that in the back of my mind, and I can't get that out of my mind that a lot of the issues that my mother had recur in the literature.

ROBERT: What that means is that the diseases that killed his mom are the very kinds of diseases that show up in his research.

KIRBY JOHNSON: And then we—towards the end, we had conversations about fetal cells, and it made us closer. And I could share my scientific background and the work that I was doing in a way that comforted her, I think to a certain degree, to know that I was investigating something that was directly related to her health issues. And towards the end, we had a lot of real nice conversations about the work that I was doing and the latest discoveries. And she would always ask—after she would ask how I was, she would say, "How's the work?"

ROBERT: Well, here's what—I think there's a chance that your fetal cells in your mom sometimes helped and sometimes hurt. So you're not gonna come out the hero, you might even come out the villain. Doesn't that sap your enthusiasm for this a little bit at some level?

KIRBY JOHNSON: Well, of course I would want to think that my cells contributed in some small way to some improvement to my mother's health. If I find out that it wasn't the case, well that's the truth. And as a scientist, I want to find the truth. Whether or not the truth is wonderful or the truth is horrible, that's what I want to find out, regardless of what the end personal outcome is.

ROBERT: And what if the truth is well, some of the time you helped, some of the time you hurt, much of the time it didn't matter? Doesn't that hurt you a little bit? Can you get up the next morning and say, "Let's find out how unimportant I am?"

KIRBY JOHNSON: [laughs] Well, that's—that is a very difficult question. I know if I were to be able to go to my mother, if I put my best effort forward to finding the truth, and even if it was a negative or was a mixed bag, or perhaps was even not really much of anything, at least I know what the truth is. And both as a son and as a scientist, that would be of value to me. I may feel unfortunate that I wasn't able to do something more than the emotional support that I could provide my mother, but I have to look at it as finding the truth.

ROBERT: Yeah.

JAD: That's nice.

ROBERT: So that's where we at land.

PRODUCER: Yeah. Happy Mother's Day.

PRODUCER: Oh, that's right. This is ...

ROBERT: Oh, Mother's Day.

JAD: Oh, yeah! This is Mother's Day. I mean, kind of.

PRODUCER: That's two weeks before.

JAD: I know that mothers really need a day. They should basically own the calendar, but since here we are chronologically near Mother's Day, happy Mother's Day.

ROBERT: You're welcome.

JAD: You've written about this on your blog, right?

ROBERT: I have, yeah. I should say ...

JAD: You should say where that is.

ROBERT: It's called Krulwich Wonders. So you just write K-R-U-L-W-I-C-H Wonders into any search engine, and there it is.

JAD: Yeah.

ROBERT: And this issue and other things many times a week.

JAD: Yeah, check it out. It's pretty good.

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[LISTENER: Hi, my name's Tom Geffen Jones from Denver, Colorado. I am a Radiolab listener. Radiolab is supported in part by the National Science Foundation, and by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. For more information about Sloan, at www.sloan.org. Thanks.]

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