The presence of leukaemia‐associated phenotypes is an independent predictor of induction failure in acute myeloid leukaemia

Immunophenotyping of acute myeloid leukaemia (AML) has controversial implications with regards to prognosis. The aims of the present study were to determine the frequency of leukaemia‐associated phenotypes (LAP) in AML and to correlate their presence with response to induction chemotherapy. We analysed bone marrow samples at diagnosis from 84 AML patients using triple staining flow cytometry with routine standard panel of monoclonal antibodies. The association of LAP and response to induction chemotherapy was evaluated retrospectively. LAP were observed in 54 (64%) patients: lineage infidelity in 19 (35%), asynchronous antigen expression in 28 (52%), and lack of expected lineage specific antigens in 19 (35%). Significant correlation was found between LAP and responses to induction chemotherapy. Response to induction chemotherapy was more frequent in the absence of LAP (P < 0.05, estimated risk ratio of 1.6, 95%CI, 1.0–2.6) in a multivariate analysis. In conclusion, our data show the presence of LAP in AML is an independent predictor for response to induction chemotherapy and risk of relapse and should be considered for counselling patients and planning therapy.     

Clinical and echocardiographic survey of the Ehlers-Danlos syndrome

Cardiac abnormalities such as mitral valve prolapse (MVP) are reported to be common features of the Ehlers Danlos syndrome (EDS), and it has been suggested that the majority of patients with type IV EDS will have cardiac involvement and vascular aneurysms. However, the evidence for valve lesions is inconsistent and often based on early clinical studies using mainly M-mode echo. We studied 33 patients (six male, 27 female; median age 35 yr) with EDS (30 type I, II or III, three type IV) and 30 age- and sex-matched controls. The study assessed skin stretch and joint hypermobility using Beighton and Contompasis scores. Echocardiographic examination included standard two-dimensional views from the parasternal and apical windows, and measurement of the aorta at four sites (annulus, sinotubular junction, arch and abdominal aorta). Echocardiographic abnormalities were found in four patients (12.1%) (one atrial septal aneurysm, one tricuspid prolapse, two MVP) and two controls (6.7%). MVP was found in 6.1% of EDS patients and 7% of controls. Seven patients had previously been diagnosed as having MVP; only two were shown to have true MVP using current criteria. None of those with type IV EDS had any echocardiographic abnormality. No patients with EDS had mean aortic dimensions outside the normal range at any of the points tested. Cardiac symptoms were more frequent amongst the patients than controls (atypical chest pain 48%, P = 0.0001; palpitation 39%, P = 0.001; exertional dyspnoea 30%). A wide range of rheumatological complaints were reported (current arthralgia 75%; recent back pain 72%, P = 0.005; recurrent dislocation 72%). Contrary to earlier published observations, we have not found an increased incidence of cardiac abnormalities in EDS. This syndrome may be relatively more benign, from the cardiac point of view, than was previously thought.      

Immunohistochemical characterization of a 183 KD myeloid-specific-DNA- binding protein in B5 fixed, paraffin-embedded tissues, and bone marrow aspirates by monoclonal antibody BM-1

A monoclonal antibody, designated BM-1, which is reactive in B5 formalin-fixed, paraffin-embedded tissues, has been generated against a cytoplasmic and nuclear antigen expressed in human myeloid precursor cells and derived leukemias. Using the avidin-biotin-complex immunoperoxidase procedure, BM-1 was found to stain selectively myeloid precursor cells in normal bone marrow and mature granulocytes in the blood. In a screen of 26 normal adult and fetal human organs fixed in B5 formalin, BM-1 was negative in all nonhematopoietic tissues with the exception of tissue granulocytes and scattered cells in the peripheral cortex of the thymus. Likewise a screen of 30 solid tumor cell lines including a spectrum of carcinomas, sarcomas, and neural-derived tumors was negative. BM-1 was also negative with 21 T and B cell lymphomas and 11 Hodgkin's disease tumors. A preliminary study of tumors of the hematopoietic system revealed that BM-1 was reactive with M2 and M3 acute myelogenous leukemias (AML), chronic myelogenous leukemias (CML) and myelomonocytic leukemias, and granulocytic sarcomas. M1, M4, M5, and M6 AML clot preparations were negative in this study, indicating that BM-1 may have a role in the histopathologic diagnosis of myelogenous leukemia. Myeloid leukemic cell lines HL-60, ML-2, KG1, and TPH-1-O showed BM-1 nuclear and/or cytoplasmic reactivity in a subpopulation of cells, but erythroid and lymphoid leukemias and all lymphoma cell lines were negative. Immunoperoxidase studies of a panel of fetal tissues showed BM-1 positive cells in the peripheral cortex of the thymus and portal myelopoietic regions of the liver at 18 weeks gestation. Finally, DNA-cellulose and solid phase radioimmunoassay (RIA) techniques developed in our laboratory demonstrate that the BM-1 antigenic domain is reactive only after binding to eukaryotic but not prokaryotic single- or double-stranded DNA. Immunoblot techniques using a DNA-cellulose purified protein sample revealed that BM-1 recognizes a 183 kD protein. These studies indicate that BM-1 is recognizing a myeloid-specific antigen that, because of its DNA binding characteristics, may have an important role in the differentiation of myeloid cells at the molecular level.     

Prediction of invasive candidal infection in critically ill patients with severe acute pancreatitis

Introduction

Patients with severe acute pancreatitis are at risk of candidal infections carrying the potential risk of an increase in mortality. Since early diagnosis is problematic, several clinical risk scores have been developed to identify patients at risk. Such patients may benefit from prophylactic antifungal therapy while those patients who have a low risk of infection may not benefit and may be harmed. The aim of this study was to assess the validity and discrimination of existing risk scores for invasive candidal infections in patients with severe acute pancreatitis.

Methods

Patients admitted with severe acute pancreatitis to the intensive care unit were analysed. Outcomes and risk factors of admissions with and without candidal infection were compared. Accuracy and discrimination of three existing risk scores for the development of invasive candidal infection (Candida score, Candida Colonisation Index Score and the Invasive Candidiasis Score) were assessed.

Results

A total of 101 patients were identified from 2003 to 2011 and 18 (17.8%) of these developed candidal infection. Thirty patients died, giving an overall hospital mortality of 29.7%. Hospital mortality was significantly higher in patients with candidal infection (55.6% compared to 24.1%, P = 0.02). Candida colonisation was associated with subsequent candidal infection on multivariate analysis. The Candida Colonisation Index Score was the most accurate test, with specificity of 0.79 (95% confidence interval [CI] 0.68 to 0.88), sensitivity of 0.67 (95% CI 0.41 to 0.87), negative predictive value of 0.91 (95% CI 0.82 to 0.97) and a positive likelihood ratio of 3.2 (95% CI 1.9 to 5.5). The Candida Colonisation Index Score showed the best discrimination with area under the receiver operating characteristic curve of 0.79 (95% CI 0.69 to 0.87).

Conclusions

In this study the Candida Colonisation Index Score was the most accurate and discriminative test at identifying which patients with severe acute pancreatitis are at risk of developing candidal infection. However its low sensitivity may limit its clinical usefulness.     

Effects of Procainamide on the Excitable Gap Composition in Common Human Atrial Flutter

The composition of the excitable gap (EG) in common atrial flutter (AFI) was determined before and during infusion of procainamide (PA) in 9 patients (6 men and 3 women; age 70 ± 7 years). The EG was determined by introducing a premature stimulus after every 20th AFI complex detected using a quadripolar electrode catheter placed just above the tricuspid valve. Diastole was scanned in 2- to 4-ms decrements to the atrial effective refractory period (ERP). The relationship between the coupling interval and the return cycle length (CL) determined a reset-response curve (RRC), which described the EG. PA (15 mg/kg) was administered during AFl over 30 minutes and RRC was repeated at maximum AFI CL. PA prolonged AF1 CL from 227 ± 29 to 296 ± 62 ms (P < 0.01) but did not terminate AFI. ERP during AFl prolonged from 169 ± 24 to 219 ± 41 ms (P < 0.01). Control EG was 57 ± 16 ms or 25%± 6% of AFl CL and on PA EG was 77 ± 30 ms (P = 0.01), which was still 26%± 7% of the CL. Without drug, RRC was mixed in eight cases demonstrating an EG composed of fully excitable tissue (10 ± 4 ms or 19%± 10% of the EG) and partially refractory tissue (48 ± 18 ms), PA did not change the duration of the fully excitable region (13 ± 10 ms or 19%± 15% of EG). Peak PA plasma concentration was 47 ± 20 μmol/L. PA prolonged AFI CL, ERP, and EG duration but did not change the proportion of AFI CL occupied by the EG. The persistence of fully excitable tissue at the head of the wavefront in the presence of PA may largely explain its inefficacy in the acute termination of common AFl.     

The Long QT Syndrome with Impaired Atrioventricular Conduction: A Malignant Variant in Infants

Distal Conduction Disease in the Long QT Syndrome. Introduction : The long QT syndrome (LQTS) is occasionally complicated by impaired AV conduction, mostly 2:1 AV block. This form of LQTS can manifest before birth or during neonatal life, and it is more sporadic than familial. It is usually an isolated disorder, although it can be accompanied by a variety of cardiovascular and other anomalies. In spite of different treatment modes, mortality is high.
Methods and Results : The reported case presented not only with 2:1 AV conduction, but also with Wenckebach episodes with impaired right and left bundle branch conduction, and decremental conduction in the His-Purkinje axis. We also observed sinus pauses and accelerated AV junctional escape beats.
Conclusion : Our findings, and similar observations by others., suggest involvement of the sinus node and the distal conduction system in this form of the LQTS. Several histologic studies have documented abnormalities within the conduction system, including apoptosis. Because of the rare occurrence and poor prognosis of the LQTS with impaired AV conduction, international guidelines for diagnosis and treatment are needed. Development of an internal cardiac defibrillator for this young age group is necessary.     

Arg-Gly-Asp-dependent occupancy of GPIIb/IIIa by applaggin: evidence for internalization and cycling of a platelet integrin

Using indirect immunofluorescence microscopy we examined the distribution and cycling of GPIIb/IIIa after binding to applaggin, a high-affinity Arg-Gly-Asp (RGD)--containing ligand. Resting, unfixed platelets were incubated with applaggin for 30 minutes at 37 degrees C, and bound applaggin was detected by an affinity-purified rabbit anti- applaggin antibody. Examination of intact cells showed a rim pattern for applaggin, consistent with its binding to the platelet surface. Staining of Triton X-100--permeabilized cells showed an intracellular pool of applaggin. Competition of applaggin binding by either AP-2, an anti-GPIIb/IIIa monoclonal antibody (MoAb) that blocks fibrinogen binding, or the synthetic peptide RGDW eliminated both surface and intracellular staining, indicating that applaggin is binding to GPIIb/IIIa in an RGD-dependent manner. Inhibition of platelet activation by PGE1 and theophylline had no effect on the observed staining patterns, indicating that cellular activation is not required for surface binding and subsequent internalization. To evaluate whether occupancy of functional binding sites on GPIIb/IIIa is required for internalization, we used mAb15, an anti-GPIIIa antibody that neither blocks fibrinogen binding nor induces the expression of ligand-induced binding sites on GPIIb/IIIa. In these studies mAb15 was internalized in a manner analogous to both AP-2 and applaggin, showing that occupancy of the RGD binding site is not required to initiate receptor internalization. To estimate the size of the newly internalized pool of applaggin, 125I-applaggin--binding studies were performed. Displacement of bound 125I-applaggin by excess unlabeled applaggin or EDTA showed that at least 17% of bound applaggin was nondisplaceable when binding was performed under conditions permitting membrane flow and internalization. These data indicate that GPIIb/IIIa is internalized in unstimulated platelets independent of cellular activation or occupancy of the functional binding site(s) of GPIIb/IIIa by RGD-containing ligands. Thus, internalization of GPIIb/IIIa may represent a mechanism by which the surface expression of this adhesion receptor is regulated.     

Transfected leukocyte integrin CD11b/CD18 (Mac-1) mediates phorbol ester-activated, homotypic cell:cell adherence in the K562 cell line

The CD11b/CD18 leukocyte integrin molecule mediates diverse neutrophil adherence-related functions, including cell:cell and cell:extracellular matrix attachments. To study the individual role of this leukocyte integrin in cell adherence in hematopoietic cells, we expressed the CD11b/CD18 complex on the surface of K562 cells, a cell line derived from an individual with chronic myelogenous leukemia in blast crisis. We used an amphotrophic retroviral vector designated LCD18SN, harboring the complete coding sequence for the CD18 subunit, to transfer the CD18 cDNA into K562 cells and select stable cell lines. The CD11b subunit in the expression plasmid pREP4 was transfected into these K562/CD18 cells by electroporation and stable cell clones were selected. These K562 cells possessed RNA and intracellular protein for each subunit, and they expressed the CD11b/CD18 heterodimer on the cell surface. When CD11b/CD18 expressing K562 cells were stimulated with phorbol myristate acetate (50 ng/mL) for 24 to 48 hours, these K562 cells formed dense cell:cell aggregates. This homotypic aggregation required both activation of the CD11b/CD18 complex and the induction of the counter- receptor for CD11b/CD18 on the conjugate cell. This cell line will (1) enable the structure-function relationships between cell activation and homotypic adherence to be assessed, (2) provide the opportunity to identify accessory molecules required for activation of the CD11b/CD18 complex, and (3) facilitate the identification of novel ligands for the CD11b/CD18 complex.