Effectiveness of bacterial screening in preventing and controlling platelet bacterial contamination / 中国实验血液学杂志

This study was purposed to investigate the effectiveness of bacterial screening with 24 hours holding in preventing and controlling bacterial contamination of platelets. Bacterial screening of apheresis platelets preserved for 24 hours was performed by using BacT/ALERT automatic bacterial culture system. The samples from 5 bags of platelet were taken in aseptic condition and were merged into 1 bag. The final sample was inoculated into aerobic and anaerobic bottle respectively for testing, meanwhile the screened platelet samples were held for 24 hours. If the platelets were cultured for 24 hours and identification of bacterial strains showed negative, the platelets could be released, and the original platelet samples should be rescreened if initiate positive was found. The results showed that in screening 8017 samples of apheresis platelets the initiate positive results were 16 (0.2%) and confirmed positive were 4 (0.05%). Out of 4 confirmed positive strains, three were Staphylococcus aureus and another was Staphylococcus auricularis. It is concluded that it is necessary for blood center to apply the method of bacterial screening of platelet with 24 hours holding as conventional screening method, which is an effective and feasible way to prevent and control bacterial contamination of platelets.

Immune tolerance induced by exosomes derived from regulatory dendritic cells of mice / 中国实验血液学杂志

The study was aimed to explore the roles of exosomes derived from regulatory dendritic cells of mice in the induction of immune tolerance. Immature DC (iDC) from mouse bone marrow cells and regulatory DCs (rDC) were induced by treating iDC with TGF-beta1 and IL-10. The phenotype of regulatory DCs and normal DCs were assayed by flow cytometry. Exosomes from immature DCs (iDex) and regulatory DCs (rDex) were isolated by ultracentrifugation and ultrafiltration. A skin transplantation model was established with the recipients BALB/c mice and the donor C57BL/6 mice. Recipients were divided into PBS control group, iDex group (injection 10 microg iDex of donor C57BL/6 mice via tail vein at days 7 and 3 before skin transplantation), rDex group (injection 10 microg rDex of donor C57BL/6 mice via tail vein at days 7 and 3 before skin transplantation). The capacity of the donor mice and the unrelated allogeneic donor mice to stimulate allogeneic T lymphocyte proliferation was examined by mixed lymphocyte culture (MLR). The results showed that TGF-beta1 and IL-10 could down-regulate the expressions of costimulatory molecules, including CD80, CD86 and CD40. The graft mean survival time (MST) in control group, iDex group and rDex group was 7.8, 10.7 and 18.8 days, respectively. There was significant difference in MST between iDex group and control group (p<0.05), and between rDex group and iDex group (p<0.01). The results of MLR assays indicated donor-specific hyporeactivity especially in rDex group, while the tolerant B/C mice were still immunocompetent to unrelated allogeneic DBA mouse. It is concluded that injection iDex or rDex of donor mice via tail vein before skin transplantation induces immunotolerance, and the effect of rDex is more significant.

Activation of random-donor platelet concentrates and platelet prepared from random-donor apheresis collections during storage / 中国实验血液学杂志

The activation of random-donor platelet concentrates and platelets prepared from random-donor apheresis collections (plateletpheresis) during storage were studied. Percentage of CD62p staining and mean channel fluorescence (MCF) of CD41 of two kinds of platelets during storage on day 0, day 1, day 3 and day 5 were determined by flow cytometry. The results showed that percentages of CD62p staining and MCF of CD41 in plateletpheresis were (18.91 +/- 6.25)%, (19.48 +/- 8.27)%, (22.82 +/- 6.06)%, (56.71 +/- 11.79)% and (8.09 +/- 2.38)%, (8.13 +/- 2.45)%, (8.44 +/- 2.51)%, (19.87 +/- 6.13)%, while the results of platelet concentrates were (30.65 +/- 12.33)%, (31.46 +/- 11.86)%, (32.51 +/- 13.05)%, (63.55 +/- 13.27)% and (10.33 +/- 4.37)%, (11.09 +/- 6.61)%, (13.46 +/- 9.69)%, (24.41 +/- 10.15)%, respectively. The platelet count and pH value were also determined. The platelet number, pH value, percentage of CD62p staining and MCF of CD41 had no significant difference within 3 days of platelet storage. The platelet number and pH value decreased significantly (P < 0.001), while percentages of CD62p staining and MCF of CD41 increased significantly (P < 0.001) on day 5 of storage. It is concluded that the quality of plateletpheresis is better than platelet concentrate.