Expression of B220 on activated T cell blasts precedes apoptosis

Superantigens are bacterial or viral products that polyclonally activate T cells bearing certain TCR β chain variable elements. For instance, Vβ8⁺ T cells proliferate in response to staphylococcal enterotoxin B (SEB) in vivo and then undergo Fas- and/or TNF-mediated apoptosis. We have recently shown that apoptotic SEB-reactive T cells express the B cell marker B220. Here we report the identification of a novel subset of CD4⁺B220⁺ T cell blasts that are the precursors of these apoptotic cells in SEB-immunized mice. Moreover, we show that the CD4^–CD8^–B220⁺ T cells that accumulate in the lymphoid organs of Fas ligand-defective gld mice stably express a form of the B220 molecule which exhibits biochemical similarities to that expressed by activated wild-type T cells, but is distinct from that displayed on the surface of B cells. Surprisingly, we also find a population of CD4⁺B220⁺ pre-apoptotic T cells in FasL-defective gld mice, arguing that these cells can be generated in a Fas-independent fashion. Collectively, our data support a general model whereby upon activation, T cells up-regulate B220 before undergoing apoptosis. When the apoptotic mechanisms are defective, T cells presumably down-regulate their coreceptor molecules but retain expression of B220 as they accumulate in lymphoid organs.     

Diastolic heart failure. Constrictive, restrictive, and pericardial

Clinical heart failure with normal systolic function is suggestive of diastolic dysfunction. This can result from myocardial or pericardial disorders. Myocardial disorders are a broad range of pathologies leading to restrictive physiology. Amyloidosis is a prototype of restrictive cardiomyopathy leading to diastolic dysfunction. Pericardial disorders leading to diastolic heart failure are usually in the form of constrictive physiology. Differentiation between restrictive and constrictive pathologies is often difficult and require careful attention to hemodynamic and Doppler echocardiographic features.     

Technique for replacing the mitral valve with a pulmonary autograft: the Ross-Kabbani operation

Replacing the mitral valve with a pulmonary autograft is an important option at the disposal of surgeons working in areas where lifelong anticoagulation is impractical. In this article we describe the technique of this operation as it has evolved through our experience with 51 patients operated on since July 1997.     

Clinical Utility of Celiac Disease-Associated HLA Testing

Background

Negative predictive value (NPV) of celiac disease (CD)-related human leukocyte antigens (HLA) DQ2 and DQ8 approaches 100 % in individual patients. However, studies evaluating its exclusionary utility in patient groups are lacking.

Aim

We aim to assess the performance of HLA testing when applied to patient groups with varying characteristics and propose evidence-based recommendations for its clinical use.

Methods

Demographic and clinical information was recorded in patients undergoing HLA testing. Using predetermined criteria, patients were classified as CD, non-CD, or indeterminate. Diagnostic yield of HLA testing was defined as the percentage of patients in whom CD could be excluded based on negative HLA test.

Results

Two hundred and fifty-six patients underwent testing for CD-related HLA DQ2 and DQ8. 102 (100 non-CD, 2 CD) patients tested HLA negative for a 98 % NPV and 39 % diagnostic yield. Diagnostic yield was highest (60 %) in patients with intraepithelial lymphocytosis plus normal IgA tissue transglutaminase antibody (IgA-tTG) and lowest in patients with positive IgA-tTG plus villous atrophy (0 %). CD was diagnosed in two HLA-negative patients, who carried half of DQ2.5 trans genotype.

Conclusions

Diagnostic yield of CD-related HLA testing varies widely depending on clinical indication. HLA testing is a practical and valuable test for most patients in whom initial evaluation for CD is inconclusive. A negative HLA result usually obviates the need for further celiac testing including endoscopy and gluten challenge. Rarely, in patients reported as HLA negative, half of HLA DQ2.5 (cis or trans) is sufficient for development of CD.     

Ultrasound guided vascular access in pediatric cardiac critical care

Introduction

Safely obtaining vascular access in the pediatric population is challenging. This report highlights our real-world experience in developing a safer approach to obtaining vascular access using ultrasound guidance in children and infants with congenital heart disease.

Methods

As part of a quality initiative, we prospectively monitored outcomes of all vascular access attempts guided by ultrasound from January 2010 to September 2010. Variables monitored included age, weight, the time from first needle puncture to wire insertion, site of insertion, number of attempts, type of line, and complications.

Results

There were 77 attempts (15 arterial and 62 venous) to obtain vascular access in 43 patients. The mean age was 15 months (6 days–11 years; median 2.5 months). The mean weight was 7.2 kg (2–46 kg, median 3.8). Success rates were 93% and 95% for arterial and venous cannulation, respectively. Mean time from first needle puncture to wire insertion was 3.9 min (0.5–15 min, median 2 min). Fifty-five (75%) central line cannulations were successful from the first puncture; 17(23%) were successful from the second puncture; and one case (2%) required three punctures. Thirty patients (45%) weighed less than 3.5 kg. This lower body weight did not affect success rate, which was unexpectedly high (96.6%). There were no associated complications.

Conclusion

Ultrasound guided vascular cannulation in critically ill pediatric patients is safe, effective and efficient. This approach had a high success rate, and was associated with zero complications in our setting.