Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) plays a critical role in downregulating T cell responses. A number of autoimmune diseases have shown genetic linkage to the CTLA-4 locus. We have ...cloned and expressed an alternatively spliced form of CTLA-4 that has genetic linkage with type I diabetes in the NOD mice. This splice variant of CTLA-4, named ligand-independent CTLA-4 (liCTLA-4), lacks exon2 including the MYPPPY motif essential for binding to the costimulatory ligands B7-1 and B7-2. Here we show that liCTLA-4 is expressed as a protein in primary T cells and strongly inhibits T cell responses by binding and dephosphorylating the TcRzeta chain. Expression of liCTLA-4, but not full-length CTLA-4 (flCTLA-4), was higher in memory/regulatory T cells from diabetes-resistant NOD congenic mice compared to susceptible NOD mice. These data suggest that increased expression and negative signaling delivered by the liCTLA-4 may regulate development of T cell-mediated autoimmune diseases.
Aims/hypothesis
We examined the effect of a standardised sympathetic stimulus, incremental adrenaline (epinephrine) infusion on cardiac repolarisation in individuals with type 1 diabetes with normal ...autonomic function, subclinical autonomic neuropathy and established autonomic neuropathy.
Methods
Ten individuals with normal autonomic function and baroreceptor sensitivity tests (NAF), seven with subclinical autonomic neuropathy (SAN; normal standard autonomic function tests and abnormal baroreceptor sensitivity tests); and five with established cardiac autonomic neuropathy (CAN; abnormal standard autonomic function and baroreceptor tests) underwent an incremental adrenaline infusion. Saline (0.9% NaCl) was infused for the first hour followed by 0.01 μg kg
−1
min
−1
and 0.03 μg kg
−1
min
−1
adrenaline for the second and third hours, respectively, and 0.06 μg kg
−1
min
−1
for the final 30 min. High resolution ECG monitoring for QT
c
duration, ventricular repolarisation parameters (T wave amplitude, T wave area symmetry ratio) and blood sampling for potassium and catecholamines was performed every 30 min.
Results
Baseline heart rate was 68 (95% CI 60, 76) bpm for the NAF group, 73 (59, 87) bpm for the SAN group and 84 (78, 91) bpm for the CAN group. During adrenaline infusion the heart rate increased differently across the groups (
p
= 0.01). The maximum increase from baseline (95% CI) in the CAN group was 22 (13, 32) bpm compared with 11 (7, 15) bpm in the NAF and 10 (3, 18) bpm in the SAN groups. Baseline QT
c
was 382 (95% CI 374, 390) ms in the NAF, 378 (363, 393) ms in the SAN and 392 (367, 417) ms in the CAN groups (
p
= 0.31). QT
c
in all groups lengthened comparably with adrenaline infusion. The longest QT
c
was 444 (422, 463) ms (NAF), 422 (402, 437) ms (SAN) and 470 (402, 519) ms (CAN) (
p
= 0.09). T wave amplitude and T wave symmetry ratio decreased and the maximum decrease occurred earlier, at lower infused adrenaline concentrations in the CAN group compared with NAF and SAN groups. AUC for the symmetry ratio was different across the groups and was lowest in the CAN group (
p
= 0.04). Plasma adrenaline rose and potassium fell comparably in all groups.
Conclusions/interpretation
Participants with CAN showed abnormal repolarisation in some measures at lower adrenaline concentrations. This may be due to denervation adrenergic hypersensitivity. Such individuals may be at greater risk of cardiac arrhythmias in response to physiological sympathoadrenal challenges such as stress or hypoglycaemia.
Introduction:
In cancer, there are survival-based staging systems and tailored, stage-based treatments. There is little personalized treatment in vascular disease. The 2019 Global Vascular Guidelines ...on the Management of CLTI proposed successful treatment hinges upon Patient risk, Limb severity, and ANatomic complexity (PLAN). We sought to confirm a three axis approach and define how increasing severity affects mortality, not just limb loss.
Methods:
Patients revascularized for incident CLTI at our institution from 2013 to 2017 were included. Outcomes were mortality, limb loss, the composite endpoint of amputation-free survival. Using Bayesian machine learning, specifically supervised topic modeling, clusters of patient features associated with mortality were formed after controlling for revascularization type. Patients were assigned to the cluster they belonged to with highest probability; clusters were characterized by analyzing the characteristics of patients within them. Patient outcomes were used to order the clusters into stages with increasing mortality.
Results:
We defined three distinct clusters as the basis for patient- and limb-centered stages. Across stages, rates of 1-year mortality were 7.6, 13.8, 18.9% and rates of amputation-free survival were 84.8, 79.3, and 63.2%. Stage one had patients with rest pain and previous revascularization who were less likely to have wounds, diabetes, and renal disease. Stage two had doubled mortality, likely related to diabetes prevalence. Stage three is characterized by high rates of complicated comorbidities, particularly end stage renal disease, and significantly higher rate of limb loss (22.6 vs. 8% in stages one and two).
Conclusion:
Using precision medicine, we have demonstrated clustering of CLTI patients that can be used toward a robust staging system. We provide empiric evidence for PLAN and detail about how changes in each variable affect survival and amputation-free survival.
Valid risk stratification schemes are key to performing comparative effectiveness research; however, for chronic limb-threatening ischemia (CLTI), risk stratification schemes have limited efficacy. ...Improved, accurate, comprehensive, and reproducible risk stratification models for CLTI are needed.
To evaluate the use of topic model cluster analysis to generate an accurate risk prediction model for CLTI.
This multicenter, nested cohort study of existing Project of Ex Vivo Vein Graft Engineering via Transfection (PREVENT) III clinical trial data assessed data from patients undergoing infrainguinal vein bypass for the treatment of ischemic rest pain or ischemic tissue loss. Original data were collected from January 1, 2001, to December 31, 2003, and were analyzed in September 2021. All patients had 1 year of follow-up.
Supervised topic model cluster analysis was applied to nested cohort data from the PREVENT III randomized clinical trial. Given a fixed number of clusters, the data were used to examine the probability that a patient belonged to each of the clusters and the distribution of the features within each cluster.
The primary outcome was 1-year CLTI-free survival, a composite of survival with remission of ischemic rest pain, wound healing, and freedom from major lower-extremity amputation without recurrent CLTI.
Of the original 1404 patients, 166 were excluded because of a lack of sufficient feature and/or outcome data, leaving 1238 patients for analysis (mean SD age, 68.4 11.2 years; 800 64.6% male; 894 72.2% White). The Society for Vascular Surgery Wound, Ischemia, and Foot Infection grade 2 wounds were present in 543 patients (43.8%), with rest pain present in 645 (52.1%). Three distinct clusters were identified within the cohort (130 patients in stage 1, 578 in stage 2, and 530 in stage 3), with 1-year CLTI-free survival rates of 82.3% (107 of 130 patients) for stage 1, 61.1% (353 of 578 patients) for stage 2, and 53.4% (283 of 530 patients) for stage 3. Stratified by stage, 1-year mortality was 10.0% (13 of 130 observed deaths in stage 1) for stage 1, 13.5% (78 of 578 patients) for stage 2, and 20.2% (105 of 521 patients) for stage 3. Similarly, stratifying by stage revealed major limb amputation rates of 4.2% (5 of 119 observed major limb amputations in stage 1) for stage 1, 10.8% (55 of 509 patients) for stage 2, and 18.4% (81 of 440 patients) for stage 3. Among survivors without a major amputation, the rates of CLTI recurrence were 9.2% (11 of 119 observed recurrences in stage 1) for stage 1, 24.9% (130 of 523 patients) for stage 2, and 29.6% (132 of 446 patients) for stage 3.
The topic model cluster analysis in this cohort study identified 3 distinct stages within CLTI. Findings suggest that CLTI-free survival is an end point that can be accurately and reproducibly quantified and may be used as a patient-centric outcome.
In the twenty years since Dr. Leo Breiman's incendiary paper
was first published, algorithmic modeling techniques have gone from controversial to commonplace in the statistical community. While the ...widespread adoption of these methods as part of the contemporary statistician's toolkit is a testament to Dr. Breiman's vision, the number of high-profile failures of algorithmic models suggests that Dr. Breiman's final remark that "the emphasis needs to be on the problem and the data" has been less widely heeded. In the spirit of Dr. Breiman, we detail an emerging research community in statistics - data-driven decision support. We assert that to realize the full potential of decision support, broadly and in the context of precision health, will require a culture of social awareness and accountability, in addition to ongoing attention towards complex technical challenges.
Merrillite, also known as "whitlockite," is one of the main phosphate minerals, along with apatite, that occur in lunar rocks, Martian meteorites, and in many other groups of meteorites. Significant ...structural differences between terrestrial whitlockite and lunar (and meteoritic) varieties warrant the use of "merrillite" for the H-free extraterrestrial material, and the systematic enrichment of REE in lunar merrillite warrants the use of "RE-merrillite." Laser Raman spectroscopy of extraterrestrial merrillite and terrestrial whitlockite confirms the absence of H in the former and presence of H in the latter. Lunar merrillite, ideally (Mg, Fe2+, Mn2+)2Ca18-x (Y,REE)x(Na2-x)(P,Si)14O56, contains high concentrations of Y+REE, reaching just over 3 atoms per 56 O atoms, or up to approximately 18 wt% as (Y,RE)2O3. In the absence of extensive Si ⇌ P substitution, the "availability" of the Na site limits Y+REE substitution to approximately 2 atoms per 56 O atoms. Higher concentrations of Y+REE, with coupled substitution of Si for P to balance charge are possible, but rare in lunar material. Intrinsically low Na concentrations in lunar rocks, combined with the typical formation of merrillite in late-stage basaltic mesostasis or residual, intercumulus melt pockets, produce these high REE concentrations. Lunar merrillite typically contains 0.1-0.4 Na atoms per 56 O atoms. For comparison, Martian merrillite contains significantly higher Na concentrations (up to 1.7 Na atoms per 56 O atoms) and much lower REE concentrations. Meteoritic merrillite has relatively low REE contents, but exists in both Ca-rich and Na-rich varieties. Concentrations of Fe and Mg in all varieties sum to near 2 atoms per 56 O atoms. Merrillite in lunar crustal lithologies typically has Mg > Fe; however, Fe-rich mare basalts contain up to 1.8 Fe2+ per 56 O. The structure of merrillite accommodates a variety of substitutions, and the compositional characteristics reflect conditions and processes specific to the parent planet.
Two independent quorum‐sensing systems control the expression of bioluminescence (lux) in the marine bacterium Vibrio harveyi. Each system is composed of an autoinducer (AI‐1 or AI‐2) and its cognate ...sensor (LuxN or LuxQ). The sensors are two‐component hybrid kinases, containing both sensor kinase domains and response regulator domains. Sensory information from the two systems is relayed by a phosphotransfer mechanism to a shared integrator protein called LuxO. LuxO is a member of the response regulator class of the two‐component family of signal transduction proteins, and LuxO acts negatively to control luminescence. In this report, missense and in frame deletion mutations were constructed in luxO that encoded proteins mimicking either the phosphorylated or the unphosphorylated form, and these mutations were introduced into the V. harveyi chromosome at the luxO locus. Phenotypical analyses of the resulting mutant V. harveyi strains indicate that the phosphorylated form of LuxO is the repressor, and that the unphosphorylated form of the protein is inactive. Analysis of the lux phenotypes of V. harveyi strains containing single and double luxN and luxQ mutations indicate that LuxN and LuxQ have two activities on LuxO. They act as LuxO protein kinases at low cell density in the absence of autoinducers, and they switch to LuxO protein phosphatases at high cell density in the presence of autoinducers. Furthermore, the timing and potency of inputs from the two systems into regulation of quorum sensing are different.
B lymphocytes spread and extend membrane processes when searching for antigens and form immune synapses upon contacting cells that display antigens on their surface. Although these dynamic ...morphological changes facilitate B cell activation, the signaling pathways underlying these processes are not fully understood. We found that activation of the Rap GTPases was essential for these changes in B cell morphology. Rap activation was important for B cell receptor (BCR)- and lymphocyte-function-associated antigen-1 (LFA-1)-induced spreading, for BCR-induced immune-synapse formation, and for particulate BCR ligands to induce localized F-actin assembly and membrane-process extension. Rap activation and F-actin assembly were also required for optimal BCR signaling in response to particulate antigens but not soluble antigens. Thus by controlling B cell morphology and cytoskeletal organization, Rap might play a key role in the activation of B cells by particulate and cell-associated antigens.
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