Background-Myocardial and renal injury commonly contribute to perioperative morbidity and mortality after abdominal aortic aneurysm repair. Remote ischemic preconditioning (RIPC) is a phenomenon whereby brief periods of ischemia followed by reperfusion in one organ provide systemic protection from prolonged ischemia. To investigate whether remote preconditioning reduces the incidence of myocardial and renal injury in patients undergoing elective open abdominal aortic aneurysm repair, we performed a randomized trial. Method and Results-Eighty-two patients were randomized to abdominal aortic aneurysm repair with RIPC or conventional abdominal aortic aneurysm repair (control). Two cycles of intermittent crossclamping of the common iliac artery with 10 minutes ischemia followed by 10 minutes reperfusion served as the RIPC stimulus. Myocardial injury was assessed by cardiac troponin I (Ͼ0.40 ng/mL), myocardial infarction by the American College of Cardiology/American Heart Association definition and renal injury by serum creatinine (Ͼ177 mol/L) according to American Heart Association guidelines for risk stratification in major vascular surgery.

Patients waitlisted for and recipients of solid organ transplants (SOT) are perceived to have a higher risk of contracting severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and death; however, definitive epidemiological evidence is lacking. In a comprehensive national cohort study enabled by linkage of the UK transplant registry and Public Health England and NHS Digital Tracing services, we examined the incidence of laboratory‐confirmed SARS‐CoV‐2 infection and subsequent mortality in patients on the active waiting list for a deceased donor SOT and recipients with a functioning SOT as of February 1, 2020 with follow‐up to May 20, 2020. Univariate and multivariable techniques were used to compare differences between groups and to control for case‐mix. One hundred ninety‐seven (3.8%) of the 5184 waitlisted patients and 597 (1.3%) of the 46 789 SOT recipients tested positive for SARS‐CoV‐2. Mortality after testing positive for SARS‐CoV‐2 was 10.2% (20/197) for waitlisted patients and 25.8% (154/597) for SOT recipients. Increasing recipient age was the only variable independently associated with death after positive SARS‐CoV‐2 test. Of the 1004 transplants performed in 2020, 41 (4.1%) recipients have tested positive for SARS‐CoV‐2 with 8 (0.8%) deaths reported by May 20. These data provide evidence to support decisions on the risks and benefits of SOT during the coronavirus disease 2019 pandemic.

The durable alloantibody responses that develop in organ transplant patients indicate long-lived plasma cell output from T-dependent germinal centres (GCs), but which of the two pathways of CD4 T cell allorecognition are responsible for generating allospecific T follicular helper (TFH) cells remains unclear. This was addressed by reconstituting T-cell deficient mice with monoclonal populations of TCR-transgenic CD4 T cells that recognised alloantigen only as conformationally-intact protein (direct pathway) or only as self-restricted allopeptide (indirect pathway), and then assessing the alloantibody response to a heart graft. Recipients reconstituted with indirect-pathway CD4 T cells developed long-lasting IgG alloantibody responses, with splenic GCs and allospecific bone marrow plasma cells readily detectable 50 days after heart transplantation. Differentiation of the transferred CD4 T cells into TFH cells was confirmed by follicular localisation and by acquisition of signature phenotype. In contrast, IgG alloantibody was not detectable in recipient mice reconstituted with direct-pathway CD4 T cells. Neither prolongation of the response by preventing NK cell killing of donor dendritic cells, nor prior immunisation to develop CD4 T cell memory altered the inability of the direct-pathway to provide allospecific B cell help. CD4 T cell help for GC alloantibody responses is provided exclusively via the indirect-allorecognition pathway.

Background. The clinical effectiveness of vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in immunosuppressed solid organ and islet transplant (SOT) recipients is unclear. Methods. We linked 4 national registries to retrospectively identify laboratory-confirmed SARS-CoV-2 infections and deaths within 28 d in England between September 1, 2020, and August 31, 2021, comparing unvaccinated adult SOT recipients and those who had received 2 doses of ChAdOx1-S or BNT162b2 vaccine. Infection incidence rate ratios were adjusted for recipient demographics and calendar month using a negative binomial regression model, with 95% confidence intervals. Case fatality rate ratios were adjusted using a Cox proportional hazards model to generate hazard ratio (95% confidence interval). Results. On August 31, 2021, it was found that 3080 (7.1%) were unvaccinated, 1141 (2.6%) had 1 vaccine dose, and 39 260 (90.3%) had 2 vaccine doses. There were 4147 SARS-CoV-2 infections and 407 deaths (unadjusted case fatality rate 9.8%). The riskadjusted infection incidence rate ratio was 1.29 (1.03-1.61), implying that vaccination was not associated with reduction in risk of testing positive for SARS-CoV-2 RNA. Overall, the hazard ratio for death within 28 d of SARS-CoV-2 infection was 0.80 (0.63-1.00), a 20% reduction in risk of death in vaccinated patients (P = 0.05). Two doses of ChAdOx1-S were associated with a significantly reduced risk of death (hazard ratio, 0.69; 0.52-0.92), whereas vaccination with BNT162b2 was not (0.97; 0.71-1.31). Conclusions. Vaccination of SOT recipients confers some protection against SARS-CoV-2-related mortality, but this protection is inferior to that achieved in the general population. SOT recipients require additional protective measures, including further vaccine doses, antiviral drugs, and nonpharmaceutical interventions. (Transplantation 2022;106: 436-446).

Tertiary lymphoid organs (TLOs) may develop within allografts, but their contribution to graft rejection remains unclear. Here, we study a mouse model of autoantibody-mediated cardiac allograft vasculopathy to clarify the alloimmune responses mediated by intragraft TLOs and whether blocking lymphotoxin-β-receptor (LTβR) signaling, a pathway essential for lymphoid organogenesis, abrogates TLO development. TLOs (defined as discrete lymphoid aggregates associated with high endothelial venules) were detectable in 9 of 13 heart allografts studied and were predominantly B cell in composition, harboring germinal-center activity. These are most likely manifestations of the humoral autoimmunity triggered in this model after transplantation; TLOs did not develop if autoantibody production was prevented. Treatment with inhibitory LTβR-Ig fusion protein virtually abolished allograft TLO formation (mean TLOs/heart: 0.2 vs. 2.2 in control recipients; P=0.02), with marked attenuation of the autoantibody response. Recipients primed for autoantibody before transplantation rejected grafts rapidly, but this accelerated rejection was prevented by postoperative administration of LTβR-Ig (median survival time: 18 vs. >50 d, respectively, P=0.003). Our results provide the first demonstration that TLOs develop within chronically rejecting heart allografts, are predominantly B cell in origin, and can be targeted pharmacologically to inhibit effector humoral responses.

Case fatality ratios for deaths within 28 d of onset in vaccinated compared with unvaccinated transplant recipients Vaccination status (n) SARS-CoV-2 RNA positive, n Deaths in SARS-CoV-2 RNA-positive patients N (%) Unvaccinated (6748) 3473 438 12.6 One dose (1738) 326 39 12.0 Two doses (39 727) 143 11 7.7 SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

In transplant, meaningful international comparisons in organ utilization are needed. This collaborative study between the United Kingdom (UK) and the United States (US) aimed to develop a kidney utilization metric allowing for legitimate intercountry comparisons.Data from the UK and US transplant registries, including all deceased donor kidneys recovered from 2006 to 2017, were analyzed. To identify a potentially comparable kidney utilization rate (UR), several denominators were assessed. We discovered that the proportion of transplanted kidneys from elderly donors in the UK (10.7%) was 18 times greater than that in the US (0.6%). Conversely, en bloc pediatric kidney transplant was more common in the US. Donation after circulatory death utilization has risen in both countries but is twice as prevalent in the UK (39% of transplants) vs the US (20%). In addition, US and UK URs are not directly comparable due to fundamental system differences. However, using a suite of URs revealed practice areas likely to yield the most benefit if improved, such as efforts to increase kidney offer acceptance in the US and to reduce postacceptance discard in the UK. Methods used in this study, including novel intracountry risk-adjusted UR trend logistic regression analyses, can be translated to other international transplant registries in pursuit of further global learning opportunities. K E Y W O R D S clinical research/practice, donors and donation: deceased, donors and donation: donation after brain death (DBD), donors and donation: donation after circulatory death (DCD), kidney transplantation/nephrology, United Network for Organ Sharing (UNOS) S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section.

O'Dowd A. Covid-19: Johnson is on back foot over next steps to control pandemic. BMJ 2020; 369: m2152.