Clinical aspects of sensitization.

1. The incidence of broad sensitization has decreased significantly over the past 8 years, probably due to a decrease in pretransplant blood transfusions. Graft survival rates among broadly sensitized patients have improved over this time period (76% graft survival at 2 years posttransplant for patients transplanted in 1995-1996 compared with 66% for patients transplanted in 1989-1990). This is probably due to an improvement in immunosuppression and a related decrease in the incidence of acute rejection episodes. 2. As has been shown before, blood transfusions, previous pregnancies and failed allografts independently increased the incidence of sensitization. It is clear that certain subgroups of patients are more likely to become sensitized, given antigenic stimulation, as evidenced, for example, by the fact that 52% of patients receiving more than 10 units of blood prior to transplant were relatively unsensitized. Males seem to be less apt than nulliparous females to become broadly sensitized, although this may be due to the lower age of nulliparous females. Asians are the least likely race to become broadly sensitized. Among multiparous Asians who received more than 5 units of blood, 27% were broadly sensitized compared with 35% of comparable Whites and African Americans. 3. The incidence of acute rejection episodes increased with increasing degrees of sensitization. About 46% of first cadaveric allograft recipients with PRA levels greater than 50% had at least one acute rejection episode within 6 months after transplantation compared with 38% of unsensitized individuals. In addition, sensitized individuals were more likely to have an episode of early acute rejection before discharge from the hospital. 4. Induction with antilymphocyte antibody preparation was more commonly used in broadly sensitized patients. However, this therapeutic modality did not reduce the incidence of rejection episodes measured at 6 months posttransplant. In addition, the use of induction therapy for broadly sensitized patients has decreased with the advent of newer immunosuppressive protocols that include Neoral, MMF and FK506. 5. There was an association between the incidence of broad sensitization and delayed graft function. Induction therapy was more commonly used in patients with both delayed graft function and broad sensitization, although the decision to use this therapeutic modality seems to be made based on the presence of broad sensitization rather than the presence of delayed graft function. 6. Choosing the optimal immunosuppressive drug regimen is an important decision in broadly sensitized individuals because of the increase in acute rejections and decrease in overall graft survival in this group. Classic teaching suggests that this group of patients should be administered induction therapy with antilymphocyte antibody preparations. Early data suggests, however, that the combination of Neoral, mycophenolate and prednisone may be the optimal regimen for these individuals with respect to graft survival and that the addition of antibody induction therapy to any of the other commonly used regimens does not improve graft survival (at least up to 3 years after transplantation).