The Rhesus (Rh) blood group is the most polymorphic human blood group and it is clinically significant in transfusion medicine. Especially, D antigen is the most important and highly immunogenic antigen. Due to anti-D, it is the cause of the hemolytic disease of the newborn and transfusion reaction. About 0.1%–0.5% of Asian people are RhD-negative, whereas in the Thai population, the RhD-negative blood type only occurs in 0.3%. Approximately 10%–30% of RhD-negative in Eastern Asian people actually were D-elute (DEL) phenotype, the very weak D antigen that cannot be detected by indirect antiglobulin test (IAT). There are many reports about anti-D immunization in RhD-negative recipients through the transfusion of red blood cells from individuals with DEL phenotype. D-elute phenotype screening in Thai RhD-negative blood donors was studied to distinguish true RhD-negative from DEL phenotype. A total of 254 Thai serologically RhD-negative blood donors were tested for RhCE phenotypes and anti-D adsorption/elution test. In addition, RhC(+) samples were tested for RHD 1227A allele by SSP-PCR technique. The RhD-negative phenotype samples consisted of 131 ccee, 4 ccEe, 1 ccEE, 101 Ccee, 16 CCee, and 1 CcEe. The 42 Ccee and 8 CCee phenotype samples were typed as DEL phenotype and 96% of DEL samples were positive for RHD 1227A allele. The incidence of RhC(+) was 46.4%, and 48 of the 118 RhC(+) samples were positive for both anti-D adsorption/elution test and SSP-PCR technique for RHD 1227A allele. The sensitivity and specificity were 96% and 100%, respectively, for RHD 1227A detection as compared with the adsorption/elution test. In conclusion, RhC(+) phenotype can combine with anti-D adsorption/elution test and RHD 1227A allele SSP-PCR technique for distinguishing true RhD-negative from DEL phenotype.

The distribution of HLA-DRB1 alleles and DQB1 alleles in 100 Thai patients with non-Hodgkin's lymphoma (NHL) was analysed using the polymerase chain reaction with sequence-specific primer (PCR-SSP) method, and the association between the disease and the presence of certain HLA class II alleles was investigated. The frequencies of HLA-DRB1*1502 and DRB1*09012 were increased while those of DRB1*0404, DRB1*0803 and DRB1*1106 were decreased. On the other hand, the incidence of HLA-DQB1 alleles was similar to that in the normal population. Interestingly, only HLA-DRB1*1502 showed a significant positive association with NHL, especially in patients < or / = 45 years and in male patients. It is concluded that the DRB1*1502 allele may contribute to NHL susceptibility in the Thai population. However, further studies on the functional roles of the HLA class II alleles are necessary to elucidate NHL susceptibility.

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