Liver transplantation and the lymphocyte crossmatch

Abstract

Hyperacute rejection related to donor-specific antibodies rarely occurs in liver transplantation, probably because of the role of Kupffer cells, sinusoidal cells, and the dual blood supply. However, the long-term outcome of liver grafts, transplanted in the context of a positive lymphocytotoxic crossmatch, is approximately 20% lower than that of grafts with a negative crossmatch. Without recipient selection based on the crossmatch, which is currently the generally accepted policy, 11% to 24% of the liver transplants will be performed with a positive crossmatch. Using the level of panel reactive antibodies, (eg > 30%) as an indicator for sensitization, a lymphocytotoxic crossmatch can be performed before transplantation on a limited number of patients, to avoid a positive crossmatch. Sometimes the medical urgency does not allow the patient to wait for a negative crossmatch. Therefore, plasmapheresis should be performed before transplantation to diminish the antibody level and the posttransplant use of prostaglandin-E and high-dose steroids should be considered to avoid the short-term immunologic complications. These measures require more study before they can become standard practices. Possibly, Mycophenolate Mofetil might be effective in preventing chronic rejection. The introduction of the flowcytometry crossmatch procedure will not only provide a more sensitive, but also a faster procedure (~4 hours), allowing a wider use of the pretransplant crossmatch test in liver transplantation. However, the increased sensitivity and speed are balanced by the much lower specificity of the positive flowcytometric crossmatch test. The most appropriate way to use flow techniques for lymphocyte crossmatching has not yet been clearly determined because of the specificity problem. In the setting of other solid organ transplantation, the presence of preformed donor-specific antibodies is linked with occurrence of hyperacute or accelerated rejection, and is likely to result in graft failure in a short period of time. Therefore, a positive crossmatch directed against donor HLA antigens is a concern in organ transplantation, especially in kidney and heart transplantation. A positive IgG crossmatch test precludes transplantation in most cases. In liver transplantation, the picture is not so clear, but probably represents a relative contraindication to transplantation.