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HCV infection has a significant impact on kidney transplant recipients over the long term and in particular affects them in the second decade. Our pilot study revealed only partial efficacy of IFN-alpha therapy for HCV-infected recipients, but with the high risk of acute rejection.

Excess of cancer in patients receiving renal transplantation is well-known in Western countries, but information in Japan remains limited. Our study examined whether excess risk is found in patients receiving renal transplantation in Japan. Between 1970 and 1995, 1155 males and 589 females underwent renal transplantation in 6 hospitals, and a total of 12,982 person-years of observation was accumulated. Malignancies developed in 2.6% of patients; O/E ratio was 2.78. Median interval from renal transplantation to tumor development was 58 months. The interval in the patients receiving medication with cyclosporine-A (CyA) (median, 42.5 months) was significantly shorter than that with non-CyA (median, 95.5 months). Median age at the diagnosis of malignancy was 40 years, which is much younger than that in the general population. Relative risk was highest in renal cancer, followed by thyroid cancer, malignant lymphoma and uterine cancer. A distribution of malignancies was different from that reported from Western countries. These findings showed the excess risk of malignancies in Japan with renal transplants, especially in male patients, similar to that observed in Western countries, though the types of malignancy were different.

The gene frequencies and haplotypic associations within the HLA region have been investigated in 916 unrelated Japanese individuals. HLA class I and class II antigens were studied by conventional serology, and class II alleles, DRB1, DRB3, DQA1, DQB1 and DPB1 were typed by using polymerase-chain reaction amplification and sequence-specific oligonucleotide probe (PCR-SSOP) method. Thirty DRB1, 3 DRB3, 8 DQA1, 15 DQB1 and 13 DPB1 alleles were found in our population. DR-NJ25, a characteristic antigen in the native American and Asian populations, was observed at 3.0%. This antigen was observed mainly with the DRB1*1403 and 1406 alleles. Twenty-seven out of 30 DRB1 alleles found in this study had a high positive linkage disequilibrium with DQB1 alleles and 20 of them had an exclusive association with one specific DQA1-DQB1 combination. The strong association between DRB1 alleles and HLA-B antigens was the most striking finding in this study. Twenty-eight out of 30 DRB1 alleles had a positive linkage disequilibrium with 24 HLA-B antigens (p < 0.01). The other two alleles, DRB1*0404 and 1402, were very rare, and their frequencies were 0.2% and 0.1%, respectively. The data presented in this population study should be useful for the studies on anthropology, organ transplantation and disease susceptibility.

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