by Christopher Gerry
figures by Abagail Burrus

A few weeks ago, a nurse took six gallons of blood out of my left arm; my body only holds about a gallon and a half of blood, so I wouldn’t be here if she had decided to keep it. The blood that was continuously returning to my right arm, however, was missing an important ingredient: peripheral blood stem cells (PBSCs). Blood stem cells are the source of all of the blood cells in the body, including the white blood cells of the immune system. My PBSCs were collected and couriered to a patient to replace the ones that had given him cancer, hopefully curing his otherwise fatal disease. I don’t know who he is, but we’re connected by the cells that now course through both of our veins.

The Match

My PBSC donation story started in 2015 when I joined the Be The Match Registry. Unlike blood donations, which can be given to the millions and millions of people who share the same blood type, PBSC donors are carefully matched to their recipients on a one-to-one basis. To facilitate matchmaking, organizations like the National Marrow Donor Program curate lists of potential donors (like the Be The Match Registry) that doctors can check when their patient needs a blood stem cell transplant. But because this procedure is so dangerous for the recipient, it is reserved for patients with life-threatening diseases that compromise the blood, bone marrow, or immune system.

Figure 1: HLAs are the key to finding a good match for blood stem cell donation. In order to donate blood stem cells, the HLAs (shown as small, colored dots) found on the donor’s cells (left) must very closely resemble those on the patient’s cells (right). There are so many possible combinations of HLAs, however, that many potential donors will never match a patient-even the complex scenario depicted above is a dramatic simplification. The more HLAs that are shared between donor and recipient, the better the match.

The key to finding a good match is a set of molecules called human leukocyte antigens (HLAs), which decorate the surface of PBSCs and most other cells (Figure 1). These “markers” distinguish your cells from potentially dangerous trespassers like viruses, bacteria, or cancer—it’s as if all of your cells share the same fingerprints. Every person harbors their own intricate set of HLA markers, and most of the donor’s markers have to be the same as the recipient’s to be deemed a match. There are so many possible combinations of these markers, however, that the vast majority of potential donors on the registry will never be able to donate (only about 1 out of 430 will do so). Thankfully, the registries contain enough potential donors that most patients find a match—nearly 30 million people are registered worldwide—but thousands still die every year due to unsuccessful searches.

HLA markers may be complicated on a molecular level, but joining the registry couldn’t have been simpler. I attended a local registration drive where volunteers took my contact information and swabbed the inside of my cheek a few times to get a high-level snapshot of what my HLA markers look like. About two years later, I learned that I had been flagged as a potential match; only 1 in 40 registry members ever receive that call. A subsequent blood test which took a closer look at those all-important HLA markers confirmed that I was the best possible match—I was going to donate.

The Preparation

As a brief aside, you might be wondering why PBSC donors register with the National Marrow Donor Program. Is PBSC donation the same as bone marrow donation? Not quite, but because bone marrow is the body’s main source of blood stem cells, the two procedures are simply different ways to achieve the same goal. The P (peripheral) in PBSC simply refers to the stem cells found in the bloodstream (i.e. not trapped in bone marrow).

Blood, however, typically doesn’t contain many blood stem cells, so my body needed to make more before I could donate successfully. For five days leading up to the donation, I received injections of a drug called filgrastim, which is typically used to treat chemotherapy patients suffering from neutropenia (low white blood cell levels). It also causes the blood stems cells in your bone marrow to make more copies of themselves, many of which get secreted into the bloodstream where they can be collected during the donation process (Figure 2). Even though filgrastim makes many patients feel as if they have the flu, the drug has been shown to be safe.

Figure 2: PBSC donation requires amplification of blood stem cell levels. 1) The amount of blood stem cells typically circulating in the bloodstream is not sufficient for PBSC donation; 2) a drug called filgrastim stimulates blood stem cell replication, which causes their levels to increase significantly.

My experience with filgrastim was less unpleasant than I had anticipated, but it certainly wasn’t enjoyable. The first two days were fine, and I was able to go about my day without disruption. As each day progressed, I developed a dull, achy feeling of “bone pain,” but it was mild and I always woke up the next day feeling better than I did the night before (the body destroys and removes filgrastim quickly). While never serious, I experienced more intense symptoms after the third and fourth injections. The achiness increased by about two notches, especially in the bones in my head and face, and I felt much more fatigued as the day shambled on. By the morning of the fifth day, I was very much ready to get rid of those blood stem cells that my bone marrow had worked so hard to produce.

The Donation

“Make yourself comfortable—you’re going to be here for a while.”

PBSC donation relies upon a technique called apheresis that continually draws blood from a donor, collects a specific part of it, and returns the rest (Figure 3); this process is also used for donations of another type of blood cell called platelets, which control bleeding by forming clots. Blood is a complicated mixture of different substances, so it must be separated into its constituent parts by a technique called centrifugation. This process separates materials of different densities into distinct layers by spinning them at very high speeds—a carnival ride called the Gravitron is essentially a human-sized centrifuge. The apheresis machine can then collect the layer that contains the blood stem cells and direct the rest of the blood back to the patient.

Figure 3: A continuous, multi-step process called apheresis makes PBSC donation possible. 1) Blood is drawn from the donor; 2) the blood is rotated rapidly (thousands of times per minute) via a process called centrifugation that separates liquids of different densities; 3) layers containing blood’s different components (PBSCs shown in bright red) form; 4) The PBSC layer is collected; 5) the rest of the blood is returned to the patient. Steps 1-5 are repeated for several hours to collect enough PBSCs for transplant, and all of the steps are continuously taking place-blood is constantly being drawn from one arm and put back into the other.

Apheresis isn’t perfect, so all of the blood in my body had to pass through the machine about four times to ensure enough PBSCs would be collected for the recipient. I couldn’t bend my elbows for the entire seven-hour procedure because I had an IV line in each arm—departures left, arrivals right. Blood cools quickly when it’s outside of the body, so the tubing just before the “arrivals” needle was snaked around a heating coil to warm the blood back to ~98 °F. This setup made normally mundane tasks, such as eating a sandwich and using the restroom, much more exciting. I was grateful that my dad and girlfriend kept me company all day and made sure that I got home safely. Although I was the only person donating, it took a team of supporters to guarantee the procedure’s success.

Any discomfort of mine, however, likely paled in comparison to that of the recipient. Soon before PBSC transplantation, he received doses of chemotherapy and/or radiation that destroyed most or all of his bone marrow and immune system. This grueling process both kills residual cancer cells and prevents the patient from rejecting the transplant. Doctors then introduced the freshly harvested stem cells into his bloodstream, allowing them to colonize the recently vacated marrow and start producing blood cells within a few weeks (Figure 4). The most serious, and sometimes fatal, complication of this procedure is graft-versus-host disease (GVHD), in which the newly generated immune cells start to attack the patient (the “host”). Avoiding GVHD is one of the many reasons why it’s important to find a close HLA match. Conversely, just as a fresh pair of eyes can notice details that have been overlooked, a new immune system can sometimes kill residual cancer cells via a poorly understood process known collectively as the graft-versus-tumor effect. Wherever, and whoever, my recipient may be, I hope my immune system is serving him well.

Figure 4: Donated blood stem cells populate the transplant recipient’s bone marrow to re-establish blood cell production and the immune system. 1) Blood stem cells are introduced into the recipient’s bloodstream; 2) these cells find their way into the patient’s bone marrow, which prior treatments of chemotherapy and/or radiation had destroyed; 3) after a few weeks of stem cell replication, the bone marrow is sufficiently re-populated to resume normal blood cell production.

The Aftermath

My recovery was brief and uneventful. Most PBSC donors fully recover within a week, and I felt normal just two days later. The donation procedure removed only the blood stem cells in my bloodstream, so my immune system was never compromised. Overall, my experience was extraordinarily positive, and I wouldn’t hesitate to do it again if given the opportunity.

You can find information about enrolling in the Be The Match Registry here. It’s free (if you’re between the ages of 18 and 45), quick, painless, and you’ll probably never have to think about it again. But if you do, it’ll be because you’ve given someone hope when they need it most. Sounds like a good deal to me.

Christopher Gerry is a fourth-year graduate student in the Department of Chemistry & Chemical Biology at Harvard University. He currently serves as Co-Editor-in-Chief of the Science in the News blog.

For More Information

A recent RadioLab episode in which PBSC donation plays a prominent role

A detailed primer from the National Cancer Institute regarding blood stem cell transplantation (both bone marrow- and PBSC-based)

Government data detailing the composition of donor registries and the growth in registry-based transplants

57 thoughts on “Never Tell Me the Odds: A first-hand account of blood stem cell donation

  1. Christopher, this is very well written. I manage a donor center for Be The Match and would love to use your graphics in educating volunteers about PBSC donation. Please contact me.

  2. Oh Christopher!
    Consider yourself hugged. I felt so much more informed
    after reading this great life saving journey. You are so

  3. My husband needs a stem cell transplant. We meet witj the transplant Dr this Friday. All I can say is thank you!

  4. This is incredibly helpful. Be the Match just contacted me about being a PBSC donor and this makes me feel a lot better.

  5. My brother 53 is doing a clinical trial for cml starting next week since meds didn’t work as hoped and I am starting the steps to see if I am able or match. I am 48 and have a few issues so I am concerned but will learn soon if I can help. Like another said previously in their comment to you…….BIG HUGS to your kindness and thoughtfulness. This world needs more stories and people like yourself. Thank you

    1. Torri,
      I was not a complete or perfect match for my brother, but I guess I was close enough and the procedure worked for him.


    2. I am a woman who just turned 49 years old.

      I found out I am the match for a 20 yrs old young man.

      Today March 19th, 2020 I will get my 1st of 5th filligratism shot and Monday I will start the donation.

      I am concerned about the “after” donation, if I will recovery and if I will stay healthy just the way I am.

      I want to go back to my kickboxing class, cycling and lifting but……we will see.

      My husband and 3 children are supporting me even though my little ones are too.young to really know what mommy is doing, and how she is jeopardizing probably her health for a …..stranger.🙏

      1. Eva, I hope this went well for you. I donated 17 years ago when I was 34, and have had no ill effects of the donation.

        Hope you and your family are well and that your recipient is holding up.

  6. I did this procedure in 2013 for my brother who had AML Leukemia when he was 60 (and I was 53). His prognosis was not very good even with the stem cell “transplant,” I think because of his age and the severity of the leukemia.

    I had no noticeable reaction to the filgrastim and the apheresis was completed in one day (they obtained enough stem cells and them some for the procedure.
    I was on my way back home (across the country) the next day, or maybe the day after (hard to remember now).
    Absolutely no side effects, and I am happy to report that my brother has made a full recovery and is doing very well almost 6 years later.
    By all means I would encourage someone to do this, it could very well save someone’s life.

    1. Thank you for posting your brother’s success story. It is very encouraging as I contemplate my friends’ upcoming procedures (see post below).

      1. Thank you for your words on this moment because Inreally need a positive word about being a donor.

    2. Thank you for your story! I am 53 and will be donating to my brother who is 68 in a few weeks. This gives me so much hope!

  7. Thank you for this excellent piece. I have a friend who will receive blood stem cells from his brother (also my friend) a week from now. While it is dismaying to learn that the influx of new blood stem cells is dangerous and perhaps fatal for the recipient, it is good to know the truth. I’m sure their eyes are wide open, and now mine are too.

  8. My husband is the recipient of Chris Gerry’s stem cells. He is 57, was diagnosed with Myelodysplastic Syndrome (MDS) at 55. He is now almost 14 months post transplant and is doing great! We just can’t express how thankful we are to Chris. While we were spending 4 months at the Mayo Clinic in Minnesota for the transplant, my husband’s first grandson was born. Because of Chris, he has the opportunity to watch him grow up. Without the transplant, he would only have had a few years of life here left. What an awesome gift to give to a total stranger! God bless Chris and all the donors.

    1. Hi Robbie, it’s been so wonderful to connect with you and your family. Best wishes for Keith’s continued remarkable recovery!

    2. My brother, aged 21, has MDS. We have just started the process of consulting with doctors about the stem cell process. Reading this article and this comment has given me so much hope for what my brother and I are about to embark on.

  9. Thank you for the amazingly detailed post! I recieved a call early this month saying I might be a match and just had my blood drawn today to see if I we are. Your post answered all the questions I had and have put my mind at ease! Thank you for donating

  10. Thank You Christopher for donating! I hope that you will get to meet your recipient later in your journey…
    Knowing that you have given another human being a second chance at life should fill your heart with warmth and joy.
    We can never thank the person who donated bone marrow that saved our son’s life 17 years ago from leukemia… We are forever grateful for his personal gift…
    Lam Do, MD

  11. Thank you Chris Gerry for this post and for your kind generous donation. I am researching this treatment option for my aplastic anemia (or leukemia) and came across your post. I am grateful for anyone who donates (any thing) because I’m living on blood transfusions until the next Step. I have four siblings so I hope one will be a PBSC match and be a willing donor. I just read from another site how people are disappointed when they find a match but later the donor backs out. So this post gives me hope. Thank you all for your kind Remarks. God bless all.

  12. My brother was diagnosed with acute B cell lymphoblastic leukemia a few months ago. I wasn’t his doctors first choice of a donor because of my age. I was disappointed because there was never a second thought about doing this for him.
    The registry did not provide the match they were looking for so I was tested and turns out I am a 50% match. We have completed all of the initial testing and the transplant process begins in one week.
    I have been trying to read as much as possible on the transplant process and came across your webpage. Thank you so much for sharing your experience. May my brother be a success story and one of the fortunate ones who beats this awful disease.

    1. Just signed up with Be The Match. This was incredibly helpful insight to what one may experience with the entire donation process. Thank you so much for sharing! What a wonderful thing to do, I hope I can match with someone in need.

  13. I’m about to donate mine in two weeks and this kind of eased my mind. I want to do it 100% but there’s still that fear. Thank you for this article!

  14. Thank you for sharing. It’s really inspiring for me since I have received a call from the local medical institution, telling me that there is a match.

    I think I could move on after reading your experience.

  15. My nephew received the call from BTM today that he is a match. His Dad passed at the age of 55 two years ago this month, his recipient is a 56 year old man

  16. I received a stem cell transplant from my brother 18 months ago….I am doing well. Quite a gift! I am continuing to recover, life is beginning to return to normal. I was 67, my brother was 57 My cells have 100% flipped to donor cells and my bone marrow biopsys have been normal! God is good!!

  17. I donated for a family member four months ago, at the age of 64, and so far it has worked out very well. My relative, close to me in age, is doing well. And it was a gift to be able to help.

    As a family donor, I had to inject myself. I practiced on an orange first, and used my thigh instead of my belly fat. It was easy to give a firm jab there. I don’t recall any major side effects from the filgrastim injections, and continued my normal workouts while taking them.

    My procedure also took seven hours. I went alone which was not the greatest. I had no appetite and didn’t eat lunch or snacks. But I sipped water throughout.

    Normally I can’t go seven hours without peeing during the daytime. After four hours on the machine I thought it was time, but it was barely worth the trouble. One of my IVs stopped working afterwards and had to be reinserted, causing a slight delay. Peeing with needles in each arm is more complicated for women than for men, I think. Wearing a loose longish dress or skirt (maybe with no underwear) would have been a good idea.

    I was able to fly home the following evening. I felt tired after the procedure, but after ten days was back to normal. After 30 days I had my blood rechecked and apparently all was good.

    Thank you for sharing your experience Chris. Your article is the best thing I’ve read from a donor perspective.

  18. Just found out today my brother is a perfect match. Called him and were looking at his schedule so as to make this as painless as possible. He is in NC and I am in Atlanta were having the procedure done at the Seattle Cancer Center. I know if everything goes well l will be out there for about 4 months. Your first hand account makes me feel better…..for my little brother😉

  19. I am a 65 year old physician and 8 months post transplant for AML. My cellular genetic profile was a recipe for disaster even with a SCT. I may well not be cured, time will tell, but I count every day a precious gift from the still anonymous donor who enabled me to walk with my wife and my daughter down the aisle months ago. I hope I will survive long enough to personally thank the person who stepped up to the plate allowing me to see a future that would not have happened and to reciprocate this kindness in mindful ways every day. As a donor the odds are small that you will be required to endure the transplant preparation process but please know that even the act of registering sends ripples that makes the world a better place.

    1. Christopher:
      I have no words to say other than THANK YOU from the bottom of my heart for sharing your story.
      Two years ago, life as I knew it changed.
      I was diagnosed with Smoldering Myeloma-High Risk based on Cytogenetics.
      Day to day, sometimes, moment to moment, my emotions change.
      One second I find myself laughing with friends, the next, overwhelming panic tries to take over-most of the time I do not allow it.
      The last bloodwork in March 2020 has changed drastically.
      My LDH has gone to 327, my MPV has increased as well as my platelets decreased, my Basophils has gone sky high.
      The doctors think perhaps there was a misdiagnosis, based on the above, as well as my Aberrant CD117+.
      I have also had from initial Bone Marrow Biopsy- significant Bone Marrow Fibrosis with the word GUARDED next to it.
      I asked the doctors based on the above and a few other things that have come to light in the past two years, if it were possible that I have Primary Myelofibrosis.
      I was told NO last year, don’t thing about it.
      The doctors now feel perhaps I may have been correct, and that a Bone Marrow Transplant is required in order to save my life.
      I am a 59 year old female who has a husband who is legally blind for the past 15 years, that needs me.
      I will NOT say I am not afraid of the thought of a BMT, however, I will say I am TERRIFIED I WILL NOT FIND A MATCH.
      You have taken some of the fear I have been holding onto, away.
      For this, I can never thank you enough.
      My age was also a factor, or so I thought, but seeing that at 65 years old and a High Risk AML, or so it appears, that you received YOUR GIFE OF LIFE and are doing well.
      I wish you a Full Recovery and a Long, Happy, Healthy Life.
      Thank you all.

  20. I am a healthy 65 y.o., a half match for my 37.y.o. son.
    I donated to my son 2 days ago.
    I has a good collection and 24 hours post transplant his WBC is going up.
    Unlike the writer, I was harvested via a central line.
    I would not hesitate to do it again.
    Blood is LIFE!!

  21. I joined the Bone Marrow Registry in 2013. Five years later, summer of 2018, I got the phone call. Ended up completing the PBSC donation. The filgrastim made my bones feel very achy. With each heartbeat came a shocking jolt to my back and sternum areas. But like you say, a small price to pay compared to those who suffer from cancer and blood diseases.

    This week, almost exactly two years later, I was finally able to contact my recipient. I’m floored that she is doing well. Science is a miracle.

  22. My wife was has leukima and is need of a Bone Marrow Transplant. Her sister had 5 out of 10 margin match and a outside donor has an 8 out of 10 match. The Dr. advised the sibling with a 5 out of 10 match is most desirable for a perfect transplant. We were moving full steam ahead with my wife’s sister as the donor, but was notified by the hospital today, my wife immune system was built up from all the blood transfusions, that her sister cannot be used anymore. We are stuck and do not have a donor in sight at this time. With your research or anyone reading this, is there any different avenues we could look at for a successful do not for transplant? Lost right now and looking for help.

    Thank you,


    1. Bob, just wanted to say I’m praying for y’all! I was matched last year (in August) and the woman I am to donate to has a very similar story to yours, we are only now (June the following year) able to set the date for the donation! It may take some time but I believe help is on its way! I hope this gives you some peace and hope that her match is out there!

  23. Christopher – your well-written description of your experience and how it relates to the current PBSC technology was awesome! One can research this topic all day long and receive tons of data but your article sums it up very nicely. I am a donor scheduled for these stem-cell inducing shots to hopefully help me sister battle and overcome her leukemia and am hopeful and confident that I’ll have a similar successful result as many of these posts.

  24. Thank you for your well written account. I have a donation scheduled in a few weeks and I have been very nervous. Your post has helped calm my nerves – thank you!!!

  25. I’m reading this while on my way to donate. I’ve been supported every step of the way with what to expect but to read a first hand experience is incredibly reassuring. Thankyou

  26. After joining the registry in 2013 (a relative needed a transplant and so all family/friends joined the registry in solidarity), I received the call last month that I was a preliminary match to someone. This week I found out that I’ve been cleared for PBSC donation. While I’m nervous (I’m the person who can’t watch herself get stuck with a needle), after reading this article I feel a lot better. Sounds like any side effects will be manageable and like others have said, it’s a small price to pay when you think about the person on the other side who is going through so much more. Thank you for being candid about your experience as it’s always better to hear about it from someone that’s actually been through it.

  27. Dr told me take Claritin while going through filgrastim shots. She said many patients have said helped with bone aches. So started the Claritin night of first shot and very fortunate did not have bone aches. Did experience headache, which went away shortly when PBSC donation started. Being able to help complete strangers is the most amazing feeling. I didn’t donate to boost my ego or be able to brag so as of now only few know about my donation. 40th Birthday and 2021 Mother’s Day will always be very rememberable for was the start of preparing for donation by getting my first filgrastim shot. I did fall in the 19% of women who needed central line. After donating kind glad did have to have central line , comforting being able to move arms and eat unassisted. D Day was 5/13/2021. Chris your article is very well written. Thank you putting information out there and big thanks being a donor.

  28. Hi Chris,
    I’m not sure if you still are active on this board or not but I’m hoping that you, or any other 26-38 y/o males, could answer some first hand questions about the entire process and its relation to trying to start a family, but from the male’s side of things. There is basically no research available at all on the matter and I am weary of what the Filgrastim might do physically to my chances of conceiving with my wife. I would love any and all first hand accounts from any younger males who have gone through this and went on to have successful pregnancies. I so appreciate any replies! Thank you all!

  29. Succeed! It could be one of the most useful blogs we have ever come across on the subject. Excellent info! I’m also an expert in this topic so I can understand your effort very well. Thanks for the huge help

  30. Took me time to read all the comments, but I really enjoyed the article. It proved to be very helpful to me and I am sure to all the commenters here! It’s always nice when you can nor only be informed, but also entertained!

  31. Thank you for his post. I am on my way back from my first injections to begin mobilising my stem calls to donate to my sister, and this has explained the process more clearly than I have seen so far in my reading. I pray that my sister’s transplant is also successful too! Very well done to you for your bravery.

  32. I am come here first time, I locate the ideal article. A debt of gratitude is in order for sharing fascinating and enlightening post.

  33. I just want to say thanks to all the donors. I had two stem cell transplants. They were back in 2003 and 2004. The first was at the beginning of my 9th grade year of school and the second was, I think, eight months later. I didn’t engraft on my first transplant, meaning it didn’t work. I was mostly stuck with no immune system for at least half a year because I had almost no immune system from all the pre-transplant chemo, so I was stuck in the isolation of my home. I did get a bad case of graft vs. host disease. I have a bunch of contractures in almost all of the joints from tightened tendons, so I am pretty weak. The doctors scared me so much because they had to let me know all the possibilities. It was also the first time my parents let me make a decision on my own treatment plan, so that didn’t help. I would still recommend it to anyone. It’s also been almost two decades since then, so lots of improvements have been made.

  34. Thank you for this very insightful of what you the donor goes through and what it means for the recipient. My nephew donated last August and today he was asked if he would now donate to the same patient through PBSC. This will take place next week and I will once again be accompanying him as his plus one. God Bless you Chris for what you and others do. Prayers for your recipients full recovery

  35. Great post! This is a very nice blog that I will definitively come back to more times this year! Thanks for informative post.

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