Hypophosphorylated TCR/CD3zeta signals through a Grb2-SOS1-Ras pathway in Lck knockdown cells

Despite the loss of proximal TCR-dependent signaling events, downstream T cell responses are paradoxically augmented in T cells with siRNA-mediated Lck knockdown (Methi et al., J. Immunol. 2005. 175: 7398-7406). This indicates that alternative Lck-independent pathways of T cell activation exist or that low levels of Lck elicit other signals than normal T cell activation. Here we report the recruitment of Grb2-SOS1 to CD3zeta of the TCR complex after prolonged anti-CD3 (OKT3) stimulation in T cells with Lck knockdown. Grb2 bound to incompletely phosphorylated ITAM1 with the pY-Y configuration in a solid-phase assay, but was excluded by ZAP-70 in the doubly phosphorylated pY-pY conformation. Ras and ERK1/2 activation was augmented after prolonged stimulation in T cells with Lck knockdown compared to control, leading to increased activation of the proximal IL-2 promoter (NFAT-AP-1). Finally, the phosphorylation of Ras-GAP was strongly suppressed in Lck knockdown cells, indicating that a Ras negative feedback mechanism is dependent on Lck.     

Aetiological risk factors are associated with distinct imaging findings in patients with chronic pancreatitis: A study of 959 cases from the Scandinavian Baltic Pancreatic Club (SBPC) imaging database

ObjectivesThe relation between aetiology and structural changes of the pancreas in patients with chronic pancreatitis (CP) is not fully understood. Earlier studies are limited by focusing on selected factors in studies of limited sample size. We aimed to use a large dataset to explore associations between aetiology and pancreatic morphology in CP.MethodsSubjects with definite or probable CP according to the M-ANNHEIM diagnostic criteria were included in this multicentre cross-sectional observational study and assessed using a standardized and validated CP imaging system. We performed multivariate logistic regression to analyse if aetiological factors adjusted for covariates were independently associated with morphological pancreatic features.ResultsWe included 959 patients (66% males). Mean (SD) age was 55 (14) years. Pancreatic structural changes were found in 94% of the subjects: 67% had calcifications, 59% main pancreatic duct dilatation, 33% pseudo-cysts and 22% pancreatic atrophy. Alcohol abuse was independently associated with pancreatic calcifications (odds ratio (OR, [95% CI]); 1.61, [1.09, 2.37]) and focal acute pancreatitis (OR; 2.13, [1.27, 3.56]), whereas smoking was independently associated with more severe calcifications (OR; 2.09, [1.34, 3.27]) and involvement of the whole gland (OR; 2.29, [1.61, 3.28]). Disease duration was positively associated with calcifications (OR; (per year) 1.05 [1.02, 1.08]) and pancreatic atrophy (OR; 1.05 [1.02, 1.08]) and negatively associated with focal acute pancreatitis (OR 0.91, [0.87, 0.95] and pseudo cysts (OR; 0.96, [0.93, 0.98]).ConclusionIn this large-scale study, etiological risk factors and disease duration in CP were independently associated with specific structural pancreatic imaging changes.     

Determinants of insulin secretion after renal transplantation

The high prevalence of post-transplant glucose intolerance and insulin resistance (IR) is associated with older age, family history of diabetes, immunosuppressive drugs, and antihypertensive therapy. However, the potential determinants of post-transplant beta-cell dysfunction are largely unknown. The objective of the present study was to address this issue in detail. A total of 167 previously nondiabetic renal transplant recipients underwent a 75-g oral glucose tolerance test (OGTT)10 weeks after transplantation. Serum glucose and insulin were measured at 0, 1, and 2 hours. Three insulin release indices (Secr(AUC), Secr(1.phase), and Secr(2.phase)) were calculated to assess the insulin secretory response as the dependent variable. To account for variations in insulin sensitivity (IS), beta-cell function was also estimated as the disposition index (DI); the product of the IS index (ISI(TX)) and Secr(1.phase). Increasing age was strongly and independently associated with a blunted insulin secretory response even after adjustment for IS (P =.001). An 80-year-old recipient had an approximately 50% lower insulin release than a 20-year-old individual, based on the linear regression model. Cytomegalovirus (CMV) disease and treatment with furosemide were both independently associated with beta-cell dysfunction (DI; P <.001 and P =.008). Patients treated with angiotensin-converting enzyme (ACE)-inhibitors had an enhanced absolute insulin release, but the DI was similar in both treated and untreated recipients. We conclude that older age is an important determinant of beta-cell dysfunction after renal transplantation. CMV disease and treatment with furosemide may also negatively influence pancreatic insulin release in renal transplant recipients.     

Hypersensitivity pneumonitis in a cluster of sawmill workers: a 10-year follow-up of exposure,symptoms, and lung function

Background:

The long-term prognosis of repeated acute episodes of hypersensitivity pneumonitis (HP) is not well described. We report on a 10-year follow-up of a 10-person cluster from a Norwegian sawmill who had all experienced relapsing episodes of HP.

Objectives:

To evaluate the health symptoms, work-related sick-leave, and lung function of 10 workers exposed to mold in a Norwegian sawmill.

Methods:

Participants were evaluated at baseline and 10 years later at follow-up. A structured interview, measurement of serum IgG antibodies to Rhizopus microsporus (R. microsporus) antigens, lung function tests, high resolution computed tomography (HRCT) of the chest, and personal measurements of exposure to mold spores and dust were completed for each participant.

Results:

At baseline, nearly all workers reported acute episodes of HP more than twice a month. At follow-up, both the frequency and intensity of symptoms had declined. Sick-leave was reduced and gas diffusing capacity improved – paralleling the gradually reduced air levels of mold spores.

Conclusions:

In spite of an initially high occurrence of symptoms, long-term clinical and physiological outcome was good. With reduced exposure to mold spores, symptoms declined and lung function was restored.     

Type 1 hyperlipoproteinemia due to a novel deletion of exons 3 and 4 in the GPIHBP1 gene

Objectives

Type 1 hyperlipoproteinemia is an autosomal recessive disorder characterized by severely elevated plasma triglyceride levels, which may lead to abdominal pain and pancreatitis, eruptive xanthomas and failure to thrive. Mutations in the genes encoding lipoprotein lipase (LPL), apolipoprotein CII (APOC2), apolipoprotein AV (APOA5), lipase maturing factor 1 (LMF1) or glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) have been found to cause Type 1 hyperlipoproteinemia.

Methods

Two sibpairs belonging to two different branches of an extended pedigree were referred for molecular elucidation for their increased plasma triglyceride levels, which untreated were >27 mmol/L. The genes LPL, APOC2, APOA5, LMF1 and GPIHBP1 were analyzed by DNA sequencing.

Results

No mutations were found in LPL, APOC2, APOA5 or LMF1. No PCR products were obtained for exons 3 and 4 of GPIHBP1 from DNA of the 4 affected subjects. Subsequent long-range PCR revealed that the four affected were homozygous for a deletion comprising exons 3 and 4 of GPIHBP1. No increase in LPL activity was found in post-heparin plasma from the subjects.

Conclusion

Homozygosity for a deletion of exons 3 and 4 of GPIHBP1 results in Type 1 hyperlipoproteinemia.