Blood Center–

The Science of Blood

TRALI Update

Every donor is important and very much needed. Recently, blood centers initiated steps to protect transfusion recipients from receiving plasma products that have an increased potential to cause Transfusion Related Acute Lung Injury (TRALI). TRALI is characterized by the rapid onset of mild to severe, and possibly even fatal, lung-related illness following the transfusion of plasma-rich products. TRALI is a fairly new and complicated issue. At Stanford Blood Center (SBC), we aim to keep our donors informed and educated about issues in the blood transfusion industry.

Explaining TRALI»
While the exact cause of TRALI is unknown, research indicates that plasma products from women who have been pregnant are more likely to contain certain antibodies associated with cases of TRALI. These antibodies are formed by the immune system in response to exposure to someone else’s white blood cells. If you have these antibodies, it poses no risk to you. Blood donations from women who have been pregnant are still used to help patients. Donations are separated into red blood cells and plasma. Red blood cells from all donors are safe for transfusion because the plasma content is minimal. Plasma from women who have been pregnant (which has a greater possibility of causing TRALI) will not be directly transfused but will be manufactured into products that prevent or slow bleeding in patients or as blood volume expansion agents.

Change to the TRALI policy for donors who have had a transfusion»
It was previously recognized that donations from people who have received a blood transfusion also contain antibodies that cause TRALI. Emerging research suggests the TRALI risk from these donors is not substantially higher than other donors. Therefore, many blood centers (including SBC) are once again making transfusable plasma products from these donations.

TRALI and platelet donors»
The AABB (American Association of Blood Banks) has recommended that blood centers have a risk reduction plan for platelet donations in place by the end of 2008. We are still formulating a strategy to maximize patient safety and minimize platelet shortages. We are in the process of evaluating testing platforms and donor eligibility screening options.

Every donation counts»
Every blood donor, whether they have been pregnant or not, saves lives. It is important to the community that all donors continue to give and give often. Thank you for your continued support.

If you have questions about TRALI, please call our Resource Nurse at (650) 725-9968.

Increasing the Odds

Most people think of Stanford Blood Center (SBC) as "only" a blood bank. While we certainly do pride ourselves on the quality of the blood products we supply to area hospitals, we are also very much committed to supporting research that saves lives. And our blood donors are an integral part of this commitment. Did you know that every time you donate, a small vial of your blood is reserved for research purposes? It is very likely that at some point, our researchers have used your blood to help people live better and longer lives.

For example, organ and bone marrow transplants are extending the lives of many. In our area, Stanford Hospitals and Clinics, long renowned for their state-of-the-art kidney, heart, liver, and Bone Marrow Transplant (BMT) centers, performs hundreds of transplants every year. Stanford Blood Center’s Histocompatibility Laboratories support the success of these transplants by providing, and developing tests that help determine organ recipient and donor organ compatibility. This collaboration towards providing the best in research and patient can be measured in lives. For example, out of 245 U.S. kidney transplant centers, Stanford’s kidney transplant center has the second-best three-year survival rate, and between the years 2000-2004, Stanford University Medical Clinics had the best one year kidney transplant survival rate in the country.

Matching a donated organ, whether from a living or deceased donor, requires performing a series of intricate tissue-typing tests that are designed to predict if there is a match between the donated organ and recipient. The goal is to decrease the possibility that the recipient will reject the organ. If a donor and a recipient are histocompatible (literally “tissue matching”), the likelihood of a transplanted organ being rejected is decreased.

Histocompatibility can only occur when the genetic material that is expressed as antigens is the same or very similar for both donor and recipient. Other than identical twins, everyone’s biology is unique and this differentiation includes the way a body reacts to foreign invaders. When an unknown substance enters our bloodstream, our bodies’ lymphocytes—a kind of white blood cell—stimulate our immune system to respond to the antigens present in foreign particles by forming antibodies that recognize and attack that specific antigen.

This defense mechanism is very useful in keeping us healthy, but if a donor organ contains human leukocyte antigens (HLA) that the organ recipient has previously formed antibodies to, histoincompatibility between the donor and recipient is almost certain, and rejection of the organ is likely to occur.

A strong HLA match lessens the chance that the recipient's body will reject the organ, so transplant professionals try to find the closest HLA match between donor and recipient as possible. To search for the best possible match, the HLA type of every potential organ recipient is determined before they are placed on an organ waiting list. When a potential donor organ becomes available, the donor's HLA type is determined as well. This data is sent to an organ-matching program called UNOS (United Network for Organ Sharing). UNOS compares the data, and determines the best possible recipient for each organ. Further tests, known as cross matches, are performed to make absolutely sure that the donor organ is suitable for the recipient.

The science of donor organ matching is fairly young, with successful transplants first being performed in the late 1950s. Nearly half of the HLA system was discovered here at SBC’s Histocompatibility Lab by former researcher Dr. Rose Payne. Our current director, Dr. Dolly Tyan, and former director Dr. Carl Grumet, both studied under Dr. Payne and have dedicated their careers towards advancing the science of predicting matches that ultimately result in better organ transplantation outcomes.

One test developed as a result Dr. Payne’s research is a cytotoxicity assay. This serological test involves placing serum containing different known HLA into individual wells on a tray. A sample of leukocytes (white blood cells) from the potential organ recipient is then added to each well in the tray. A specially trained technician examines the cells in each well to determine if the recipient’s existing antibodies have reacted against the antigens in each well. If cell death in a well has occurred, it is likely that the potential donor recipient has developed an antibody for that particular antigen. This data is then collected and used to match potential recipients’ HLA profiles with that of the donor organ.

This serum used in the assay is often produced from the research tubes we collect from our blood donors. Dr. Grumet explains that our donors’ normal variations in antibodies help the lab by providing the material necessary to perform the assays: “having access to a large normal population is important in allowing us to pick out individual components of patients’ serum.”

For years, cytotoxicity assays have been used to determine compatibility, and have resulted in countless successful matches. However, because of error in reading results, and possible pollution of the assay with other reactive molecules, these tests are not entirely sensitive or specific in absolutely defining an organ recipient’s HLA reaction profile. New tests that are more effective at detecting antibodies have recently been developed and are fast replacing the cytotoxicity assay method.

One test, called Luminex, works by attaching a single known antigen to a microscopic bead. Serum from the organ donor is then reacted with the bead and a signal is emitted. A laser reads the signal and can not only detect any reactions of antibodies present in the donor serum to the antigen attached to the bead, but can measure the strength of the signal the reaction creates, indicating the sensitivity of the antibody to the antigen. This data is collected and used to match donors to recipients.

These new technologies and their resulting ability to more accurately predict potential transplant failure have the potential to change the way organ donations are managed. In the next Science of Blood article, we’ll discuss the possible impact new testing may have on the current organ matching system, explore other HLA testing platforms, and examine the significant contributions SBC researchers are currently making towards increasing the odds that a transplant will be successful.

Michelle Bussenius, May 2007

Part 2:

Although transplant acceptance rates have increased greatly since the first organ transplants were performed decades ago, many people who need transplants are, for various reasons, unable to receive one, or experience rejection after transplant. Researchers, including ones here at SBC, are continuously seeking new tests, treatments, and technologies that will allow more people (in the U.S. alone, there are an estimated 74,000 patients awaiting a kidney transplant) to find a match, and be successfully transplanted.

SBC’s HLA Laboratory Director, Dr. Dolly Tyan, has dedicated her life’s work to discovering ways to save lives through improving transplant matching tests and protocols. Dr. Tyan’s connection with SBC spans several decades, beginning in the early ‘70s when, shortly after receiving her master’s degree in Biological Sciences, she joined SBC as a Research Assistant. Tyan, under the direction of Dr. Carl Grumet, studied serology (in general, the study of the antibody content in blood serum) and trained alongside the late Dr. Rose Payne—a noted expert in tissue typing, and pioneer in transplant matching research.

After leaving SBC, Tyan moved to Southern California, received her PhD in Microbiology and Immunology, and became Director of the Cedars-Sinai Medical Center Transplantation and Immunogenetics Laboratory and a professor at the David Geffen School of Medicine at UCLA. One focus of her research involved discovering ways to overcome barriers in finding matches for patients with high levels of antibodies.

As mentioned in Part I of Increasing the Odds, the best organ matches occur when the donor tissue and recipient are as compatible as possible, and cross-match studies are negative, meaning that the organ recipient does not have antibodies that may react with HLA (human leukocyte antigens) present in the donor organ. A positive cross-match indicates that the patient has developed anti-HLA antibodies to those present in the organ tissue, and almost assures that a transplant will fail.

Finding an organ match is difficult enough, and unfortunately, for patients who are highly HLA sensitized to many different HLA types—meaning that they have high levels of pre-formed anti-HLA antibodies—finding a match is next to impossible. Moreover, if such patients are transplanted, they suffer very high rates of allograft loss (organ rejection).

And the number of patients awaiting transplant who are highly HLA sensitized is growing. In 2003, an estimated 32% of patients awaiting a kidney transplant had           
HLA antibodies. To respond to this population, Dr. Tyan has sought ways to decrease patients’ HLA sensitivity enough to allow transplant to occur. Tyan, and other researchers, discovered that IVIG therapy, (Intravenous immunoglobulin) effectively provides this window of opportunity to allow HLA sensitized patients to receive a kidney. IVIG products are derived from human plasma and have been used for decades to treat primary immunodeficiency disorders.

During clinical trials, a high-dose IVIG product, designed to desensitize the organ recipient to HLA, is administered to selected patients prior to transplant. Before IVIG treatment is considered, tests are first performed that determine the patient’s antibody specificity. Once specificity is determined, a cytotoxicity assay is performed. This test involves reacting IVIG with the donor’s antibodies to see if cell death occurs. If the IVIG appears successful in inhibiting cell death, the patient receives a number of IVIG doses, and hopefully, will become desensitized to HLA and able to receive a transplant.

IVIG therapy has enabled transplantation of patients previously considered untransplantable, and, in concert with new diagnostic techniques, has resulted in many positive outcomes. Dr. Tyan believes that improved organ testing platforms, IVIG, and other pre-and-post transplant therapies have the potential to dramatically increase the number of patients eligible for transplant, and provide better matching between donor organ and patient.

Dr. Tyan asserts, “What we are learning now has the potential to change organ-matching policy.” Dr. Tyan returned to Stanford as Director of the HLA Laboratory in 2006 and brings to SBC not only her many years of experience, but a new mission. She and other researchers are working to encourage The United Network for Organ Sharing (UNOS) to adopt more emerging tests and treatments into their organ matching protocol. UNOS is the national organization that is responsible for the entire organ matching and allocation process and data collection for every transplant occurring in the United States. Currently, UNOS relies upon cross-matching, an arguably outdated technique, to determine organ donor and recipient matches.

Dr. Tyan believes that a policy change in how UNOS determines matches can save lives. Increasingly, clinical trials and studies are demonstrating the efficacy of new organ matching tests and pre-operative treatments, and changes in organ matching policy are sure to become reality in the near future. Despite her significant contributions, Dr. Tyan is modest about her accomplishments, and describes her life’s work as gratifying “when what you know how to do really helps.” And here at SBC, we’re grateful to Dr. Tyan and researchers worldwide for their tremendous efforts in discovering ways to improve and extend lives.

Michelle Bussenius, December 2007

Stanford Blood Center to Begin Testing for Chagas' Disease

Stanford Blood Center will follow the recommendations of the American Association of Blood Banks (AABB) and begin testing all blood collected for Chagas’ disease on March 5, 2007. Currently, the FDA encourages, but does not require, blood banks to screen for this parasitic disease. Screening will consist of testing samples of all donated blood using an FDA-approved testing system. This test screens for the specific antibody produced by the immune system in response to the presence of the disease. Samples that test positive will receive additional testing to confirm the results. Any positive units of blood will be destroyed, and the donor notified.

Chagas’ is a parasitic disease that occurs only in the continental Americas, most often in Latin America. The Centers for Disease Control (CDC) estimate that as many as 11 million people living in Mexico, Central, and South America are carriers of the disease. In recent years, studies have shown that incidence of the disease in the United States and Canada is on the rise in regions with growing Latino immigrant populations. In one recent study, the American Red Cross found that in Los Angeles County as many as one in 5400 people are carriers of the disease.

In North America, it is reported that 12 people have contracted the disease through organ transplant or blood transfusion during the last 20 years. This number is almost certainly underreported as Chagas’ disease is often asymptomatic in healthy individuals.

The parasite that causes Chagas’ disease is mainly transmitted by triatomine bugs, also known as kissing, or reduviid bugs. These blood-sucking parasitic bugs receive the infective T. cruzi parasite by biting an infected animal or person. An infected bug then is capable of spreading the T. cruzi parasites through their feces. After the bug bites and ingests a host’s blood, it defecates. A person can become infected if T. cruzi parasites in the bug feces enter the host’s body through mucous membranes, such as through the eyes, nose, or mouth, or breaks in the skin. 

People can also become infected by consuming uncooked food contaminated with feces from infected bugs; through congenital transmission (from a pregnant woman to her baby); blood transfusion and organ transplantation; and accidental laboratory exposure.

Chagas’ disease has an acute and chronic phase. Both phases can be symptom-free or life-threatening, depending upon the health of the individual. The acute phase lasts for the first few weeks or months of infection and is most often either asymptomatic or characterized by flu-like symptoms including fever, fatigue, body aches, headache, rash, loss of appetite, diarrhea, and vomiting.

Physical symptoms of an infection can include mild enlargement of the liver or spleen, swollen glands, and localized swelling in the area where the parasite entered the body. Symptoms that develop during the acute phase generally recede within a few weeks or months, but the infection persists.

During the chronic phase, the infection may remain silent for decades or even an entire lifespan. Some people, especially those with weakened immune systems, may develop more serious, even life-threatening symptoms of the disease. These symptoms can include cardiac complications, such as cardiomyopathy (an enlarged heart), heart failure, altered heart rate or rhythm, and sudden death by cardiac arrest. Intestinal complications that interfere with normal digestive functioning may also occur, including megaesophagus and megacolon (an enlarged esophagus or colon, respectively).

Most people infected with Chagas’ remain asymptomatic throughout their lifetime and are not aware that they are carriers of the disease. Approximately 30 percent of people infected will exhibit serious symptoms during their lifetimes. Treatment options are limited and most effective during the acute stage of the disease. An antiparasitic treatment that kills the parasite is available through the Centers for Disease Control (CDC). Symptomatic treatment, such as medication and pacemakers for those with cardiac symptoms, is standard care for those who have developed chronic cardiac or intestinal problems from the disease.
Stanford Blood Center, along with many other blood centers nationwide, is committed to proactively responding to any emerging threats to the blood supply. We are confident that our efforts ensure the quality of the blood products we supply to our area hospitals.

For more information about Chagas’ disease, visit the CDC Web site at http://www.cdc.gov/ncidod/dpd/parasites/chagasdisease/default.htm.

Michelle Bussenius, February 2007

TRALI - Tranfusion Related Acute Lung Injury

For over half a century, transfusion researchers have developed many tests and processes designed to keep the blood supply safe. As a result of their efforts, blood banks have virtually eliminated the transmission risk of bacterial contamination and many potentially fatal blood-borne pathogens, including HIV and Hepatitis B and C.

Recently, researchers in transfusion medicine have been investigating
TRALI, or transfusion related lung injury.  In recent years, TRALI has replaced incompatible blood type transfusion error as the number one cause of transfusion mortality. The FDA reports that there is currently a one unit in 220,000 transmission rate of TRALI.  Because of this potential risk, the FDA is encouraging blood centers and transfusion facilities to address this threat. 

TRALI is characterized by a rapid onset of lung-related illness following the transfusion of blood products. In most cases, symptoms appear within one to six hours of transfusion and appear very similar to ARDS, or acute respiratory distress syndrome. The patient may experience shortness of breath, fever, and accelerated heart rate. In severe cases, the patient may require mechanical ventilation to assist breathing. Approximately six to ten percent of TRALI cases prove fatal to the recipient. 

Exactly why TRALI is acquired and who will contract the disease is still under investigation. One theory speculates that antibodies present in the donor blood product attack the blood recipient’s immune defense, or white blood cells. Antibodies are unique proteins created by an individual’s immune system that identify and neutralize any foreign components, such as bacteria and viruses, in the body. These antibodies apparently attack the specific white cells that contain either Human Leukocyte Antigens (HLA), or Human Neutrophil Antigens (HNA), which in turn release substances that damage the lining of the lungs, resulting in non-cardiac pulmonary edema, or the build up of fluid in the lungs.

According to this model, for the transfusion recipient to be at risk of TRALI his or her white blood cells must express the specific HLA or HNA receptors to which the blood donor has formed antibodies. Women who have had multiple births, as well as people who’ve received transfusions, transplants, or tissue grafts are more likely to have developed antibodies that will be present in their donated blood. Antibodies are more concentrated in high plasma blood products such as apheresis platelets and FFP (fresh frozen plasma). Whole blood and cryoprecipitate contain lesser amounts of antibody concentrations.

Another less likely TRALI theory suggests that lipids, or fat cells, present in donated blood products somehow become activated during storage and form antibodies to the recipient’s neutrophils, causing the resultant lung injury.

The AABB (American Association of Blood Banks) has conferred over the issue of how to take preventive measures to reduce the incidence of TRALI. As a result, a TRALI incidence tracking system, where incidences of the disease are carefully recorded and monitored, is to be immediately implemented. In addition, there is a mandate for blood banks nationwide to reduce the number of high-antibody containing donations in whole blood products and FFP by November 2007, and in platelets by November 2008.

Currently, there is no consensus decision on exactly how to reduce the collection of high antibody containing blood products. The FDA may require blood banks to take actions to minimize collecting high plasma products from high-risk donors. Such actions may include changes to donor screening questionnaires or the recruitment of specific donors for high-plasma blood products.

Stanford Blood Center is responding to TRALI by forming a task team to address these upcoming requirements. Meetings will be held between HLA lab personnel, our medical directors, and transfusion services physicians.  Best practices will be mapped out in order to our compliance with these FDA and AABB regulations and to enhance the safety of the blood components we provide to our patients.

Michelle Bussenius, November, 2006

Stanford Medicine Resources:

Footer Links: