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We compared hepatitis B virus (HBV) surface antigen, anti-hepatitis C virus (HCV) antibody, and HCV RNA quantification in frozen and freeze-dried serum samples to assess the usefulness of freeze-dried sera for detection of HBV and HCV. The results indicated that freeze-dried sera as well as frozen sera can be useful for serological and molecular biological analyses of HBV and HCV.

Since radiation exposure affects the immune system as well as risk of various cancers, we have commenced an “immunogenome” study to look at genetic susceptibility to radiation-associated cancers. HLA class I molecules are known to regulate various immune and inflammatory responses. In this study, we examined effects of radiation exposure on individual susceptibility to gastric cancer based on HLA Class I ( HLA-A, -B, -C ) polymorphisms. This study comprised 150 gastric cancer patients and 300 controls. HLA genotype distribution among the controls not exposed to atomic-bomb radiation was almost identical to that in the general Japanese population. Comparison between non-exposed gastric cancer patients and non-exposed controls showed no statistically significant relationship between gastric cancer risk and HLA-B or HLA-C genotypes. However, frequency of HLA-A*2601 , one of the HLA-A genotypes, was significantly lower among cases (3.7%) than controls (18.3%), with P HLA-A*2601 among the gastric cancer patients (average radiation dose: 0.8 Gy) (18.8%) was almost the same as frequency among the controls (15.8%). Risk elevation by radiation was most prominent in HLA-A*2601 , compared with other genotypes. These results suggest that HLA-A*2601 may be involved in decreased gastric cancer risk among non-exposed people and that, among those with the HLA-A*2601 allele, radiation exposure may increase gastric cancer risk. On the basis of this finding, we conducted further analysis of association between the HLA-A*2601 allele and plasma levels of various inflammatory markers along with analyses of pathological typing and H. pylori infection.