Scott Hoeckele sets up HLA typing using molecular methods.
The success of an organ transplant depends on many factors, but results from the HLA lab can be critical in the final decision. Find out why this particular lab has such a major impact on transplant clinical outcomes.
Getting Down to the Basics
Human leukocyte antigens (HLA) are proteins that serve as markers on most cells in a person’s body. The immune system uses these markers to recognize which cells belong in your body … and which don’t. Antigens also play a part in stimulating the development of antibodies, which seek out and destroy foreign matter. While this action acts as a defense against pathogens, it can also lead to rejections of organ transplants.
“Let’s say a transplant patient has antibodies directed at antigen A1 and A2,” explained Jane Kearns, MT(ASCP), CHS
, technical manager of the HLA Laboratory. “Transplanting an organ that’s positive for these antigens would lead to a more difficult post-transplant course … and the patient might ultimately lose the graft.” In other words, the closer the match between a patient’s HLA markers and those of the donor, the lower the potential for developing donor-specific antibodies and the greater the chance for a successful outcome.
Determining which antibodies a transplant patient has -- and doing a crossmatch to determine if they would have a detrimental effect on the donor organ -- is the main responsibilities of the HLA lab, one of the 26 clinical laboratory servicesoffered by the Department of Pathology and Laboratory Medicine. This typing is part of a transplant patient’s initial evaluation and continues through post-transplant follow-ups. The lab’s 17 technologists perform these screenings for every one of HUP’s transplant patients with the exception of those waiting for a liver. “HLA supports all of the other transplant services, including kidney, pancreas, islet cell, heart, and lung, as well as autologous and allogeneic bone marrow transplants.”
Malek Kamoun, MD, PhD, director of the Immunology Lab, said these regular screenings are critical because, while a person’s antigens never change, antibodies can. For example, he said, “women develop antibodies through pregnancy and people who undergo transfusions and transplants can also develop antibodies.”
The results of these antibody screenings are saved in both the HLA database as well as that of the United Network for Organ Sharing (UNOS), which manages the country’s organ transplant system.
HLA typing is also performed on all donor organs. Gift of Life (the region’s organ procurement agency that coordinates distribution of organ material) sends blood samples of every donor organ to the Hershey Medical Center for testing, the results of which are also uploaded on the UNOS data base. As a result, when a request for a crossmatch comes in to the HLA lab from a transplant coordinator, “we already have a fairly good idea if the recipient-donor pair will be compatible or if there’s a possibility of incompatibility,” Kearns said.
Crossmatching to Confirm Compatibility
Still, crossmatching is never taken lightly. It’s a slow process –- each crossmatch takes up to six hours -- and there are no shortcuts. “We’re very vigilant,” said Marilyn Eisenstadt, HLA technologist. “There are serious ramifications of making any mistake.”
It’s a huge challenge, Kamoun agreed, “ with no tolerance for errors.”
The call for a crossmatch can occur at any time -- day or night. “Once a donor becomes available, we drop everything and proceed with the donor crossmatches,” Kearns said.
Generally, the transplant coordinator sends the lab a list of potential recipients to be crossmatched with a single donor organ. For each crossmatch, the tech uses patient sera stored in one of several large freezers in the lab and harvested cells from donor blood specimens. In most cases, the crossmatch is done prior to the actual transplant. However, when there are time restrictions, such as with a heart and lung transplant, “we perform a virtual crossmatch before the transplant, which is based on the antibody screening information entered into the UNOS database,” Kearns said. The actual crossmatch is done post-transplant.
In addition to running the crossmatch, the tech checks a patient’s historical data and antibody profiles. “How the patient developed antibodies is important,” Kamoun said. “It’s of more concern if it’s from a previous transplant than a blood transfusion.”
Kamoun said that, for heart transplant candidates, when test results indicate an increased risk of rejection, the transplant team works closely with the HLA lab to make a final decision. “Generally speaking, if the patient has a high risk of rejection due to HLA incompatibility but is stable, the transplant won’t be done,” Kamoun said. However, if that same patient were in dire need of a transplant, “we’ll work with the transplant team to define compatibility criteria based on more aggressive treatment aimed at decreasing the antibody level.”
Recently, the lab switched to a new data base (HistoTrac). Kearns and her team worked tirelessly for months to create a mechanism for moving data from the old database system to HistoTrac without corrupting it in any way. “We didn’t want the change in our database to impact our ability to support the transplant team.” The new system automatically transfers patient information directly from instruments into the lab’s database, thus eliminating errors from manual data entry. It also automatically uploads into UNOS and the National Bone Marrow Registry.
On average, the HLA lab performs typing on more than 2,700 samples and antibody screening on more than 5,600 patients each year. “The work is hard,” Kearns said, “but there is much satisfaction when a high-risk patient gets a transplant and has a successful outcome.”
HLA Lab Rises to the Occasion
When it comes to compatibility between donor and recipient, bone marrow transplants have much more stringent requirements than solid organs. As a result, matches are often difficult to find, even in the National Bone Marrow Registry which keeps a list of over 18 million donors throughout the world. Once a potential match is found, the confirmatory HLA (human leukocyte antigen) testing can take up to 10 days; the transplant occurs within a few weeks of confirmation. As Joanne Hinkle, RN, BSN, OCN, CHTC, Unrelated Bone Marrow Donor Coordinator, noted, “A bone marrow transplant is not normally an emergent situation.”
But that was not the case earlier this year for a leukemia patient at HUP in dire need of a bone marrow transplant. Hinkle found only one potential donor on the Registry but there was a big problem: he was in another country and in a place where having his blood drawn would be extremely difficult. “The situation was absolutely critical. We couldn’t put it off because who knew when another matching donor might become available.”
Working with the donor center in the originating country, Hinkle was able to have the donor brought to a donor center in this country within a couple days, but he could only stay for a week. His blood sample was Fed Exed overnight to HUP and Jane Kearns, MT(ASCP), CHS, technical manager of the HLA lab, and her team went into overdrive to do the necessary typing.
“They worked around the clock and got results back within two days,” Hinkle said. “Their flexibility was amazing.”
Their efforts were not for naught. The donor was a match. Within a week, the bone marrow donation was hand carried to HUP and the transplant went ahead.
“The patient got through his transplant and continues to recover,” Hinkle said. “And we could not have done it without the efforts of the HLA lab.”
Maria Tague does sample processing in preparation for the HLA testing.