Innovative application of immunologic principles in heart transplantation

Each year, approximately 2,200 heart transplants are performed in the United States. As our understanding of the immune system grows, new tools are being developed to find compatible organ donors and to help with immune surveillance after transplantation. The purpose of this article is to review 3 of these techniques: the virtual crossmatch, the Cylex ImmuKnow assay, and the AlloMap test.

Two authors (S.A.M. and J.C.) independently performed a literature search with the PubMed database using the key words ImmuKnow, Allomap, and virtual crossmatch in conjunction with heart transplantation. Articles were selected for inclusion if they had a primary focus on the use of virtual crossmatch in heart transplantation, the Cylex ImmuKnow assay, and the AlloMap test. Articles were not excluded on the basis of sample size but were excluded if they did not include heart transplant patients.

The virtual crossmatch is a technique that is being used successfully in heart transplant candidates to predict compatibility of donor organs by comparing the potential recipient's HLA-specific antibodies with the HLA type of the prospective donor. The ImmuKnow assay is a noninvasive blood test that measures the strength of immune activity, allowing clinicians to predict risk of infection and possible rejection in heart transplant patients. The AlloMap test is a noninvasive test that quantifies intracellular mRNA levels in mononuclear cells in peripheral blood samples using real-time polymerase chain reaction; this test has been shown to distinguish the dynamic changes in gene expression that occur in the presence or absence of acute cellular rejection.

As the science of transplant immunology advances, transplant cardiologists are taking advantage of the growing fund of knowledge to help their sensitized transplant candidates increase their chances of finding a compatible donor heart and are using commercially available tests to monitor the immune system and rule out rejection after transplantation.