Speaking of bratwurst and bone marrow transplants…

After working at the Hutchinson Center for nearly 20 years, I know quite a bit about bone marrow and stem cell transplantation. But some recent conversations about this miraculous process of introducing a new immune system as a treatment (and hopefully cure) for blood cancers and diseases surprised me.

Recently, I was chatting with my sister-in-law, Jenny about her pending allogeneic transplant to treat her multiple myeloma.

Since Jenny didn’t have a relative who was a close enough match, she’d just found out that her transplant donor is a 23-year-old German male. We joked about whether she might have a sudden affinity for lederhosen and bratwurst along with her new blood-forming system.

His stem cells would be flown from Europe to the Seattle Cancer Care Alliance, the Hutchinson Center’s treatment arm, where Jenny’s receiving her care.

Jenny’s oncologist said that in addition to having a new blood type after the transplant, her blood would be male. Wait a minute. What? Blood has gender? And matching a donor and patient doesn’t begin with the same blood type? Really?

Clearly I know a lot less about transplants than I thought.

Since one of the best parts of my job is having an all-access pass to brilliant minds who don’t usually mind my pesky questions, I assuaged my curiosity by sitting down with Dr. Hootie Warren, one of our oncologists.

Dr. Hootie Warren

He shared several eye-opening transplant facts:

Matching by blood type—If you need bone marrow or stem cells donated and don’t have a compatible family member, a global search for a match is undertaken through registries.

We know that blood type (A, B, AB or O) needs to match for a blood transfusion to be successful. But Warren said that isn’t necessarily true with a transplant.

The basis of the A, B, AB, and O blood types are specific proteins (antigens) that are found on the surface of red blood cells. Type A has A antigens, type B has B antigens, type AB has A and B antigens, and type O has neither. If the donor’s red blood cells carry an antigen against which the recipient makes an antibody, that’s a potential recipe for trouble. So if we mix blood types A and B together, the antibodies attach themselves to the red cells, causing them to clump together.

While matching blood types are preferable for a transplant donor and patient, if the red blood cell count of the donation is low enough, the two blood systems can peacefully coexist until the patient’s red cells are replaced and/or destroyed by the donor’s.

Turns out the most important matching feature is…

Histocompatibility—That mouthful simply means the ability to share tissues. About 40 years ago, Hutchinson Center founders and other researchers around the world discovered that in order for transplants to work, genetic characteristics on the short arm of chromosome 6 need to match. This game-changing finding ushered in the modern age of transplantation.

Those characteristics are human leukocyte antigens, or HLA. HLA typing is the process of testing blood or tissue samples from a patient who needs a transplant and from any potential donor to see how closely they match based on 10 HLA molecules. The more HLA molecules two people share, the better the match. Well-matched immune systems will not see each other as foreign and are less likely to attack each other. Jenny’s lucky—she’s a 10 out of 10 match with her donor.

Gender—First, a quick high school biology refresher: In humans, whether a person is male or female is determined by their two sex chromosomes. Females have two X chromosomes and males have an X chromosome and a Y chromosome. Gender is present in the immune system and blood-forming cells, so Jenny’s blood is now male. That conversion needed help, though. If she were not immune-suppressed, she would reject the transplant.

Warren said in these so-called sex mismatches, my sister-in-law’s situation is optimal because a female patient with a male donor has a lower risk of graft-vs.-host disease than other gender combinations. A male patient with a female donor, in contrast, is more likely to get GVHD because the transplanted female cells can recognize the male recipient’s tissues carrying a Y chromosome as foreign and attack the tissues.

Allergies—Transplant patients will inherit their donors’ allergies eventually, but it may take many years to manifest since patients are initially immune-suppressed and allergies are immune responses.

Immunizations—Since the new immune system supplants the old one, transplant patients have the same disease risks as babies and must redo childhood immunizations about six to nine months after transplantation. Jenny must wait to get certain “live virus” vaccines (like measles, mumps, rubella and chickenpox) until two years post-transplant.

Transfusions—If a current or former transplant patient needs a blood transfusion, regular blood won’t do. They typically need blood treated with radiation to kill off certain white blood cells that can cause a potentially deadly reaction.

Do you have any other questions we didn’t answer? Let us know and we’ll run them by our experts.

By Colleen Steelquist
Quest science writer