SUMMARY Although Foxp3+ regulatory T cells (Tregs) require interleukin-2 (IL-2) for their development, it has been unclear whether continuing IL-2 signals are needed to maintain lineage stability, survival, and suppressor function in mature Tregs. We generated mice in which CD25, the main ligand-binding subunit of the IL-2 receptor, can be inducibly deleted from Tregs after thymic development. In contrast to Treg development, we find that IL-2 is dispensable for maintaining lineage stability in mature Tregs. Although continuous IL-2 signaling is needed for long-term Treg survival, CD25-deleted Tregs may persist for several weeks in vivo using IL-7. We also observe defects in glycolytic metabolism and suppressor function following CD25 deletion. Thus, unlike developing Tregs in which the primary role of IL-2 is to initiate Foxp3 expression, mature Tregs require continuous IL-2 signaling to maintain survival and suppressor function, but not to maintain lineage stability.

Serum PCT is more reliable laboratory marker for the early diagnosis of SSI after elective colorectal cancer surgery, compared with conventional inflammatory indicators. PCT could serve as an additional diagnostic tool for the early identification of SSI to improve clinical decision making.

This cross-sectional study aimed to investigate the post-acute consequences of COVID-19. We conducted a self-administered questionnaire survey on sequelae, psychological distress (K6), impairments in work performance (WFun), and COVID-19–related experiences of stigma and discrimination in two designated COVID-19 hospitals in Hiroshima Prefecture, Japan, between August 2020 and March 2021. The prevalence of sequelae was calculated by age and COVID-19 severity. Factors independently associated with sequelae or psychological distress were identified using logistic regression analysis. Among 127 patients who had recovered from COVID-19, 52.0% had persistent symptoms at a median of 29 days [IQR 23–128] after COVID-19 onset. Among patients with mild COVID-19, 49.5% had sequelae. The most frequent symptoms were olfactory disorders (15.0%), taste disorders (14.2%), and cough (14.2%). Multivariate analysis showed that age was an independent risk factor for sequelae (adjusted odds ratios [AOR] for ≥ 60 years vs. < 40 years 3.63, p = 0.0165). Possible psychological distress was noted in 30.7% (17.9% of males and 45.0% of females). Female sex and the presence of sequelae were independent risk factors for psychological distress. Of all participants, 29.1% had possible impairments in work performance. Experiences of stigma and discrimination were reported by 43.3% of participants. This study revealed the significant impacts of Long COVID on health in local communities. A large-scale, long-term cohort study is desired.

Regulatory T cells (Tregs) are required for the maintenance of immune tolerance and adoptive Treg infusion therapy has become a promising approach to suppress immune responses in diseases such as autoimmunity and transplant rejection. However, one critical challenge of Treg therapy is the requirement of in vitro expansion of functionally stable Tregs while preventing either the contamination of T effector and/or emergence of unstable pathogenic Tregs. Recent studies showing distinct metabolic requirements of T effectors and Tregs suggest that manipulation of cell metabolism may be an attractive strategy to achieve this goal. Here we show that human thymically derived Tregs (tTregs) and in vitro induced Tregs (iTregs) from naive T cells engage glycolysis equivalently upon activation. However, inhibiting glucose metabolism via 2-deoxy-D-glucose (2DG) has distinct effects on each of these subsets. While 2DG treatment at the onset of activation significantly reduced the proliferation and expression of suppressive molecules such as ICOS and CTLA-4 in tTregs, its effect on FOXP3 expression was small. In contrast, 2DG treatment during iTreg induction modestly decreased their proliferation but strongly reduced both ICOS and FOXP3 expression. Importantly, both Treg subsets became insensitive to 2DG after day 3 post activation with little effect on either proliferation or FOXP3 expression while T conventional Th0 cells showed reduced proliferation under the same conditions. Moreover, 2DG treatment at day 3 did not impair the suppressive capabilities of Treg subsets. Collectively, these findings suggest that there is a distinct temporal requirement of glycolysis in each of the activated human Treg subsets and T conventional cells. Furthermore, 2DG treatment at the onset as a strategy to impair contaminating T effector cell proliferation is unfavorable for optimal Treg generation as well.

Through multiple mechanisms, regulatory B cells (Breg) have been shown to play an important role in the development of allograft tolerance. However, a careful understanding of the role of antigen‐specificity in Breg‐mediated allograft tolerance has remained elusive. In experimental models of islet and cardiac transplantation, it has been established that Bregs can be induced in vivo by anti‐CD45RB ± anti‐TIM1antibody treatment, resulting in prolonged, Breg‐dependent allograft tolerance. The importance of Breg antigen recognition has been suggested but not confirmed through adoptive transfer experiments, using tolerant WT C57BL/6 animals challenged with either BALB/c or C3H grafts. However, the importance of receptor‐specificity has not been formally tested. Here, we utilize the novel ovalbumin‐specific B cell receptor transnuclear (OBI) mice in multiple primary tolerance and adoptive transfer experiments to establish that Breg‐dependent allograft tolerance relies on antigen recognition by B cells. Additionally, we identify that this Breg‐dependent tolerance relies on the function of transforming growth factor‐β. Together, these experiments mark important progress toward understanding how best to improve Breg‐mediated allograft tolerance.

Summary In transplantation, innate immunity plays a pivotal role in immunosurveillance and host defence against microbes and neoplastic cells. Liver‐resident NK cells express TNF‐related apoptosis‐inducing ligand (TRAIL), which distinguishes them from conventional NK cells. In this study, we investigated the impact of mTOR inhibition on liver‐resident NK cells in comparison with that on splenic NK cells in a mouse model. In mice that received everolimus (EVR) for 7 days (range: 0.0125–0.25 mg/kg/day), the proportion of splenic NK cells was unchanged, whereas the number of liver NK cells including TRAIL+ NK subpopulation increased for all doses of EVR. Consistently, liver‐resident NK cells from the EVR‐treated mice displayed enhanced cytotoxicity against TRAIL‐sensitive neoplastic cells. EVR treatment inhibited the transition of the immature subset of liver NK cells to a mature state. The negative regulator of NK cells FoxO1 was activated as a consequence of impaired mTORC2‐dependent AKT phosphorylation. Activated FoxO1 both reduced T‐bet expression and induced TRAIL expression, thereby inhibiting NK cell maturation and promoting the antitumour activity of the immature subset of liver NK cells in response to EVR treatment. These findings indicate that EVR treatment enhances the antitumour activity of immature liver‐resident NK cells through TRAIL upregulation.

Previous studies have found that preferential accumulation of regulatory T (Treg) cells in liver allografts during acute cellular rejection (ACR) is associated with less severe rejection, suggesting a role of Treg cells in preventing excessive progress of ACR. We investigated the impact of single nucleotide polymorphisms (SNPs) in the Forkhead box P3 (FOXP3) gene, a master regulator gene of Treg cells, on ACR severity in liver transplant (LT) recipients. In total, 102 living donor LT patients were enrolled in this study and categorized into no rejection (n = 86), steroid‐sensitive acute rejection (SSAR; n = 11), and steroid‐resistant acute rejection (SRAR; n = 5). FOXP3 SNPs –3499 A/G (rs3761547), –3279 A/C (rs3761548), and –924 A/G (rs2232365) were genotyped using the polymerase chain reaction restriction fragment length polymorphism technique. T‐cell responses to allostimulation were evaluated by the mixed lymphocyte reaction assay. We found no statistical association between the FOXP3 SNP genotype frequencies and ACR incidence. However, significantly higher incidence of SRAR was observed in LT patients with the FOXP3 rs3761548 A/C+A/A genotype than in those with the C/C genotype (A/C+A/A versus C/C; no rejection, SSAR, SRAR, 85.71%, 0%, 14.29% versus 83.58%, 16.42%, 0%, respectively; P =  0.0005). The mixed lymphocyte reaction assay performed at the time of ACR diagnosis showed higher anti‐donor CD4+ T‐cell responses in patients carrying rs3761548 A/C+A/A than in those with the C/C genotype (P =  0.019). No significant association was observed between the incidence of SRAR and either rs3761547A/G or rs2232365 A/G. Infectious complications and overall survival were not related to FOXP3 SNPs. Conclusion: Our findings indicate that FOXP3 SNP rs3761548 A/C might be a predisposing factor for SRAR after liver transplantation. (Hepatology Communications 2017;1:406–420)

We investigated the impact of polymorphisms in host innate immunoregulatory genes on the development of infectious complications after kidney transplantation (KT). The single-nucleotide polymorphisms (SNPs) of C1QA [276 A/G], FCGR2A [131 H/R], and FCGR3A [158 F/V], genes encoding the Fc gamma receptor (FcγR), were analyzed in 81 KT recipients in relation to the occurrences of postoperative infectious complications within 30days after KT. Consistent with a lower affinity of the isoform encoded by the FCGR3A [158 F] to both IgG1 and IgG3, a significantly higher incidence of urinary tract infections (UTIs) was observed in the FCGR3A [158 F/V or F/F] individuals (65.5%) than in the FCGR3A [158 V/V] individuals (34.5%) following KT. The combination of FCGR2A and FCGR3A SNPs further stratified the incidence of UTIs, regardless of C1QA SNP following KT. No differences were observed in the incidence of fungal or cytomegalovirus infections with respect to the 3 gene polymorphisms. In conclusion, our findings indicate that FcγR SNPs are predisposing factors for UTIs after KT. This study provides a foundation for further prospective studies on a larger scale.