Standardization for CD34-positive cell (CD34⁺) count has been promoted in Japan since the first unrelated peripheral blood stem cell transplantation (UPBSCT) was performed in 2011. In 2016, an external quality assessment (EQA) study was conducted for the first time in Japan, leading to a reduction in inter-laboratory variations by the second EQA in 2017. Here, we investigated the variations and changes in CD34⁺ count by examining pairs of values from collection and transplant sites in each UPBSCT. From the Japan Marrow Donor Program registry, 1,047 CD34⁺ counts at collection sites were obtained. Among these, 257 CD34⁺ counts were obtained from 117 transplant sites, including 244 data on the method at both sites. The paired values showed a strong correlation (r²=0.854), but outliers with up to a five-fold difference were observed. A single-platform method was used at both sites for 159 data pairs, while a dual-platform method was used at one or both sites (DP group) for the remaining pairs. In 2016-2018, the difference rate (difference/mean) was significantly lower than that in 2011-2015, especially in the DP group. However, in 2019-2020, the difference rate tended to increase, suggesting the need for continued education in cell enumeration methods.

For manufacture of chimeric antigen receptor (CAR) T cells, mononuclear cells and CD3+ T cells are collected from the patient, Even with sufficient cell collection, however, manufacturing failure occurs at a constant rate. In this study, to evaluate characteristics of T cells that may lead to CAR-T cell manufacturing failure, 32 cases which underwent tisagenlecleucel production between July 2020 and September 2022 were selected and their lymphocytic surface markers and exhaustion markers were analyzed. The evaluated samples were cryopreserved as apheresis products and after defrosting, their cell viability, surface markers (CD45, 3, 4, 8) and exhaustion markers (PD-1, CTLA4, TIM3, LAG3) were analyzed by flow cytometry. Manufacturing was successful in 29 cases (90.6%) and failed in 3 (9.4%). The only significant difference between the 2 groups was in the number of CD4+ cells with surface markers (p=0.02). In contrast, no differences were seen with regard to exhaustion markers. These findings may suggest that CD4+ cell number is related to manufacturing failure. However, sample size in this study was small, and further investigation with increased case studies is required.

A 43-year-old female with acute lymphoblastic leukemia received an umbilical cord blood transplant and required frequent red blood cell and platelet transfusions. On day 29 after the transplant, platelet transfusion was started based on the appearance of the blood bag and swirling. After 15min, the patient's blood pressure and arterial oxygen saturation had decreased, and fever, chills, and shivering appeared. Based on the symptoms, anaphylactic shock was suspected, and hydrocortisone, epinephrine, and glucagon were administered. Blood culture was performed for possible septic shock. Bacterial identification tests of blood and residual samples of the platelet bag showed E. coli with matched serotypes, species, and pulsed-field gel electrophoresis patterns. Endotoxin level in the residual sample of the platelet bag was >2,000pg/ml, and endotoxin produced by E. coli contamination in the platelet bag was therefore considered to have caused her shock and related symptoms. Bacterial contamination of blood products is a rare but potentially lethal complication. Current transfusion systems cannot completely prevent bacterial contamination. Reducing the risk of contamination requires the introduction of systems such as the automated microbial detection system, which can identify trace amounts of bacteria.