Graft dysfunction in chronic antibody-mediated rejection correlates with B-cell-dependent indirect antidonor alloresponses and autocrine regulation of interferon-γ production by Th1 cells.

Chronic antibody-mediated rejection, a common cause of renal transplant failure, has a variable clinical phenotype. Understanding why some with chronic antibody-mediated rejection progress slowly may help develop more effective therapies. B lymphocytes act as antigen-presenting cells for in vitro indirect antidonor interferon-γ production in chronic antibody-mediated rejection, but many patients retain the ability to regulate these responses. Here we test whether particular patterns of T and B cell antidonor response associate with the variability of graft dysfunction in chronic antibody-mediated rejection. Our results confirm that dynamic changes in indirect antidonor CD4+ T-cell responses correlate with changes in estimated glomerular filtration rates, independent of other factors. Graft dysfunction progressed rapidly in patients who developed unregulated B-cell-driven interferon-γ production. However, conversion to a regulated or nonreactive pattern, which could be achieved by optimization of immunosuppression, associated with stabilization of graft function. Functional regulation by B cells appeared to activate an interleukin-10 autocrine pathway in CD4+ T cells that, in turn, impacted on antigen-specific responses. Thus, our data significantly enhance the understanding of graft dysfunction associated with chronic antibody-mediated rejection and provide the foundation for strategies to prolong renal allograft survival, based on regulation of interferon-γ production.

Differentiation of Human Induced Pluripotent Stem Cell into Macrophages.

As a model to interrogate human macrophage biology, macrophages differentiated from human induced pluripotent stem cells (hiPSCs) transcend other existing models by circumventing the variability seen in human monocyte-derived macrophages, whilst epitomizing macrophage phenotypic and functional characteristics over those offered by macrophage-like cell lines ( Mukherjee et al., 2018 ). Furthermore, hiPSCs are amenable to genetic manipulation, unlike human monocyte-derived macrophages (MDMs) (van Wilgenburg et al., 2013 ; Lopez- Yrigoyen et al., 2020 ), proposing boundless opportunities for specific disease modelling. We outline an effective and efficient protocol that delivers a continual production of hiPSC-derived-macrophages (iMACs), exhibiting human macrophage surface and intracellular markers, together with functional activity. The protocol describes the resuscitation, culture, and differentiation of hiPSC into mature terminal macrophages, via the initial and intermediate steps of expansion of hiPSCs, formation into embryoid bodies (EBs), and generation of hematopoietic myeloid precursors. We offer a simplified, scalable, and adaptable technique that advances upon other protocols, utilizing feeder-free conditions and reduced growth factors, to produce high yields of consistent iMACs over a period of several months, economically.

Effect of Optimized Immunosuppression (Including Rituximab) on Anti-Donor Alloresponses in Patients With Chronically Rejecting Renal Allografts.

RituxiCAN-C4 combined an open-labeled randomized controlled trial (RCT) in 7 UK centers to assess whether rituximab could stabilize kidney function in patients with chronic rejection, with an exploratory analysis of how B cell-depletion influenced T cell anti-donor responses relative to outcome. Between January 2007 and March 2015, 59 recruits were enrolled after screening, 23 of whom consented to the embedded RCT. Recruitment was halted when in a pre-specified per protocol interim analysis, the RCT was discovered to be significantly underpowered. This report therefore focuses on the exploratory analysis, in which we confirmed that when B cells promoted CD4+ anti-donor IFNγ production assessed by ELISPOT, this associated with inferior clinical outcome; these patterns were inhibited by optimized immunosuppression but not rituximab. B cell suppression of IFNγ production, which associated with number of transitional B cells and correlated with slower declines in kidney function was abolished by rituximab, which depleted transitional B cells for prolonged periods. We conclude that in this patient population, optimized immunosuppression but not rituximab promotes anti-donor alloresponses associated with favorable outcomes. Clinical Trial Registration: Registered with EudraCT (2006-002330-38) and www.ClinicalTrials.gov, identifier: NCT00476164.

Rapidly growing left atrial myxoma: a case report.

INTRODUCTION: Left atrial myxomas are rare benign tumors of the heart. They vary widely in size, and very little is known about their growth rate. The reported growth rates of left atrial myxomas from several published case reports appears to vary from no growth, to between 1.3 to 6.9 mm/month in diameter within patients with established myxoma who have not undergone surgery. CASE PRESENTATION: We present the case of a rapidly growing pedunculated left atrial myxoma in a 62-year-old asymptomatic Caucasian woman found incidentally during routine transthoracic echocardiography. Our patient was attending her annual valve clinic assessment for moderate aortic regurgitation, and her two previous consecutive transthoracic echocardiography scans performed 12 and 24 months prior to this appointment had demonstrated a clear left atrium and aortic regurgitation of moderate severity. CONCLUSIONS: To the best of our knowledge, our case is the first to provide images of absence and presence of myxoma from transthoracic echocardiography scans taken a year apart, with estimated growth rate of 2.2 mm/month. Rapidly growing myxoma may be mistaken for thrombus, and may require urgent surgical excision to reduce the risk of associated complications such as thrombo-embolic events, sudden cardiac death and removal of a possibly malignant tumor. The potential for rapid growth should be considered if there is a plan to delay surgery. Furthermore, it would be pertinent to consider annual echocardiography in patients presenting with clinical features suggestive of cardiac myxoma such as constitutional symptoms, as these tumors may be rapid growing and may only become apparent on subsequent echocardiography.