The Kg-antigen, RhAG with a Lys164Gln mutation, gives rise to haemolytic disease of the newborn.

The Kg-antigen was first discovered in an investigation of a mother whose infant had haemolytic disease of the newborn (HDN). The antibody against the Kg-antigen is believed to be responsible for HDN. The Kg-antigen is provisionally registered under the number 700045, according to the Red Cell Immunogenetics and Blood Group Terminology. However, the molecular nature of the Kg-antigen has remained a mystery for over 30 years. In this study, a monoclonal antibody against the Kg-antigen and the recombinant protein were developed that allowed for the immunoprecipitation analysis. Immunoprecipitants from the propositus' red blood cell ghosts were subjected to mass spectrometry analysis, and DNA sequence analysis of the genes was also performed. A candidate for the Kg-antigen was molecularly isolated and confirmed to be a determinant of the Kg-antigen by cell transfection and flow cytometry analyses. The Kg-antigen and the genetic mutation were then screened for in a Japanese population. The molecular nature of the Kg-antigen was shown to be RhAG with a Lys164Gln mutation. Kg phenotyping further clarified that 0.22% of the Japanese population studied was positive for the Kg-antigen. These findings provide important information on the Kg-antigen, which has been clinically presumed to give rise to HDN.

Application of the bactericidal activity of epsilon-poly-l-lysine to the storage of human platelet concentrates.

BACKGROUND: epsilon-Poly-l-lysine (epsilon-PLL) is a polypeptide comprising approximately 30 l-lysine subunits generated by bond formation between alpha-carboxy and epsilon-amino groups. It is an approved antimicrobial food preservative in Japan. However, the efficacy of epsilon-PLL as an antibacterial additive for storage of human platelet concentrates (PCs) is not known. STUDY DESIGN AND METHODS: Staphylococcus aureus, Bacillus cereus, and Klebsiella oxytoca (20 colony-forming units/mL) were inoculated into 100% plasma PCs or PCs containing 80% platelet (PLT) additive solution with 5.0 mmol/L potassium and 1.5 mmol/L magnesium (PAS-IIIM) and 20% plasma (PAS-IIIM PCs). Next, a range of epsilon-PLL concentrations up to 200 and 50 microg/mL were added to plasma PCs and PAS-IIIM PCs, respectively, and the bacterial count was determined on Days 1, 2, 5, and 8. The quality of the PCs was also determined. RESULTS: Bacterial growth was inhibited at epsilon-PLL concentrations of 200 and 50 microg/mL in the plasma and PAS-IIIM PCs after 8 days of incubation. The percentage of CD62P-positive PLTs was higher in plasma PCs treated with 200 microg/mL epsilon-PLL and in PAS-IIIM PCs treated with 50 microg/mL epsilon-PLL than in the respective controls without epsilon-PLL. There were no remarkable differences in the other variables, that is, PLT number, mean PLT volume, pH, aggregability, percentage of PAC-1-positive cells, lactate dehydrogenase release, and plasma K and Na concentrations between the epsilon-PLL-treated PCs and the controls. CONCLUSIONS: epsilon-PLL inhibited the growth of bacteria in the PCs and did not considerably affect the quality of PCs, except CD62P expression. Further studies are required to estimate the in vivo effectiveness and safety of epsilon-PLL-treated PCs.

Frequency of bacterial contamination of platelet concentrates before and after introduction of diversion method in Japan.

BACKGROUND: Bacterial contamination of platelet concentrates (PCs) is the major infectious risk in transfusion medicine. To evaluate the necessity of implementing novel strategies for the reduction of bacterial contamination, it is necessary to establish a precise contamination frequency in PCs. STUDY DESIGN AND METHODS: The frequency of bacterial contamination in PCs issued by the Japanese Red Cross was determined using expired PCs before and after the implementation of the diversion method. The culture method was designed such that it yields the least possibility of false-negative results: platelet specimens were sampled after at least 4 days of storage and the inoculum volume was 10 mL for both aerobic and anaerobic bottle cultures. RESULTS: Of the 21,786 PCs cultured, 36 (0.17%) were confirmed to be bacterially contaminated before the implementation of the diversion method. After its implementation, the number of contaminated PCs decreased to 11 of 21,783 (0.05%) with a reduction rate of 71% and the number of contaminations of clinical importance was 4 (0.018%) excluding PCs positive for Propionibacterium acnes. The frequency of contamination by bacteria presumed to originate from donors' blood did not decrease. CONCLUSION: The effect of the diversion method on the frequency of bacterial contamination is robust. The low incidence of septic reactions after PC transfusion in Japan in spite of the contamination frequency being comparable to those in Western countries and the noninstitution of culture screening suggests the importance of a short shelf life (72 hr) for PCs introduced in Japan.