藤井 紀恵

The development of human mesenchymal stromal/stem cell (MSC)-based therapy has focused on exploring biological nanoparticles secreted from MSCs. There is emerging evidence that the immunomodulatory and regenerative effects of MSCs can be recapitulated by extracellular vesicles released from MSCs (MSC-EVs). Off-the-shelf allogeneic human MSC products are clinically available to treat acute graft-versus-host disease (GVHD), but real-world data have revealed the limitations of these products as well as their feasibility, safety, and efficacy. MSC-EVs may have advantages over parental MSCs as drugs because of their distinguished biodistribution and importantly dose-dependent therapeutic effects. Recent research has shed light on the role of microRNAs in the mode-of-action of MSC-EVs. A group of specific microRNAs alone or in combination with membrane proteins, membrane lipids, and soluble factors present in MSC-EVs play key roles in the regulation of GVHD. In this concise review, we review the regulation of T cell-mediated adaptive immunity and antigen-presenting cell-mediated innate immunity by MSC-EVs and the direct regenerative effects on damaged cells in association with the immunopathology of GVHD.

INTRODUCTION: Quantitative measurement of anti-A/-B antibody titers is important during ABO-incompatible living kidney transplantation (ABOi-LKT). METHODS: We conducted a multi-institutional study to measure the antibody titers using the automated column agglutination technique (auto-CAT) and tube test (TT) method in ABOi-LKT recipients. Statistical analysis was performed to evaluate the two methods. RESULTS: We examined 111 samples from 35 ABOi-LKT recipients at four institutions. The correlation coefficient of the two methods was >0.9; the concordance rate and clinically acceptable concordance rate for the IgG titers were 60.4% and 88.3%, respectively. Perioperative status did not influence the statistical significance. Parallel changes were observed in the IgG antibody titers measured using the auto-CAT or TT technique by desensitizing therapy in time-course monitoring. CONCLUSION: Auto-CAT is comparable with the TT technique and is feasible for IgG anti-A/B antibody titration in ABOi-LKT recipients.

SARS-CoV-2 infection has been reported to be associated with a positive direct antiglobulin test (DAT). In this study, an analysis of 40 consecutive coronavirus disease 2019 (COVID-19) cases from December 2020 to September 2021 in Japan revealed that patients of 70 years and over were predisposed to a positive DAT. DAT positivity was related to a decrease in the hemoglobin level. Anemia in DAT-positive COVID-19 patients was attributed to hemolysis, which was corroborated by high reticulocyte counts and an increase in the red blood cell distribution width. Human leukocyte antigen (HLA)-DRB1*12:01 and DRB1*12:02 were exclusively found in DAT-positive COVID-19 patients. In silico assays for the Spike protein of SARS-CoV-2 predicted several common core peptides that met the criteria for a B cell epitope and strong binding to both HLA-DRB1*12:01 and DRB1*12:02. Among these peptides, the amino acids sequence TSNFR, which is found within the S1 subunit of SARS-CoV-2 Spike protein, is shared by human blood group antigen Rhesus (Rh) CE polypeptides. In vitro analysis showed that the expression of HLA-DR in CD4+ T cells and CD8+ T cells from a DAT-positive patient was increased after pulsation with TSNFR-sequence-containing peptides. In summary, positive DAT is related to enhanced anemia and to HLA-DR12 in the Japanese population. A peptide sequence within SARS-CoV-2 Spike protein may act as an epitope for IgG binding to RBCs in DAT-positive COVID-19 patients.

A 43-year-old Japanese male, who had undergone open liver surgery for tumor resection, presented with decreased hemoglobin levels on Day 13 post-emergency-release transfusion of 16 units of Fy(a +) red blood cells. As the anemia was accompanied by increased lactate dehydrogenase, indirect bilirubin, and reticulocytes, as well as decreased haptoglobin, it was attributed to hemolysis. In the diagnostic workup for hemolytic reaction, the direct antiglobulin test result for IgG was positive and the antibody dissociated from the patient's peripheral red blood cells was identified as anti-Fya (titer, 4). The hemolytic reaction was transient (approximately 10 days), of moderate severity, and did not result in any obvious organ damage. However, a single compatible red blood cell transfusion of 2 units was required on Day 17 after the causative transfusion. Notably, HLA typing revealed that the patient carried the HLA-DRB1*04:03 allele, which has been implicated in immunogenicity and induction of anti-Fya response in Caucasian populations. In summary, this is the first documented case of definitive anti-Fya-mediated delayed hemolytic transfusion reaction associated with HLA-DRB1*04:03 in the Japanese population.

ヒト間葉系幹細胞(間葉系間質細胞/human mesenchymal stromal/stem cell:MSC)は制御性免疫細胞である。間葉系幹細胞の造血細胞移植後GVHDにおける免疫制御メカニズムは複雑であり、さまざまな免疫細胞に対して液性因子や細胞接着を介して作用する。近年では間葉系幹細胞が放出する細胞外小胞(extracellular vesicle:EV)の寄与が重要視されている。ヒト間葉系幹細胞の骨髄以外の代替ソース開発が進められてきたが、最近ではiPS細胞作製技術を応用し製造された間葉系幹細胞製剤の臨床応用がはじまっており、間葉系幹細胞を応用した細胞治療のgame changerになるか注目される。(著者抄録)

In the original publication of the article, the Figs. 4 C, F and 5 B, C were published with unexpected appearance of dots.