By Dr. Chris Gonzalez, Assistant Medical Director, Stanford Blood Center
The human leukocyte antigen (HLA) system helps the immune system differentiate between a body’s own tissues and those that are foreign (e.g. invaders such as viruses and bacteria). HLA system antigens are completely different from most antigens found on red blood cells. These antigens are found on platelets, lymphocytes and most tissues and organs in the body.
The production of anti-HLA antibodies can be stimulated by pregnancy as well as transfusion of certain blood products. The more times a woman has been pregnant the greater the likelihood that she will make anti-HLA antibodies. Though not dangerous to the woman, transfusion of blood products containing such antibodies can be harmful to the patient and for this reason we do not recruit new donors into our platelet program who have had one or more pregnancies.
In April 2013, we began testing for these antibodies in all of our existing platelet donors who have ever been pregnant as they are more likely to test positive. In addition, we now retest all female platelet donors who have been pregnant since their last donation.
As mentioned above, patients transfused with blood products containing HLA antigens (such as platelets) are also at risk for developing anti-HLA antibodies. In some cases these antibodies may render regular transfused platelets ineffective. When platelet transfusion is ineffective in such patients, special platelets must be selected with an appropriate HLA type. At SBC, we HLA type many of our platelet blood donors. As a result, when a patient at the hospital needs platelets of a specific HLA type, we are quickly able to check our inventory of pre-typed platelets and donors and quickly supply the appropriate product or ask a donor to come in and donate. Although the identities of the donor and recipient remain anonymous, there is nonetheless a special and rare opportunity for the donor to experience more of a direct relationship with the recipient.
Stanford Blood Center is proud to be among the first in the country to provide HLA compatible platelets.