Internal quality control and external quality assurance in testing for antiphospholipid antibodies: Part I--Anticardiolipin and anti-β2-glycoprotein I antibodies.

Over 30 years since it was first described as a discrete clinical entity, the antiphospholipid antibody syndrome (APS) remains a challenge for both laboratory workers and clinicians in a wide range of specialties. In addition to the presence of appropriate clinical features, the diagnosis of APS also fundamentally requires the finding of positive antiphospholipid antibody (aPL) test result(s), which comprise clot-based assays for the identification of lupus anticoagulant (LA) and immunologic ("solid-phase") assays such as anticardiolipin antibodies (aCL) and anti-β2-glycoprotein I antibodies (aβ2GPI). This article is the first of two that review the process for, and provides recommendations to improve, internal quality control (IQC) and external quality assurance (EQA; or proficiency testing) for aPL assays.

Assessment of cell concentration and viability of isolated hepatocytes using flow cytometry.

The assessment of cell concentration and viability of freshly isolated hepatocyte preparations has been traditionally performed using manual counting with a Neubauer counting chamber and staining for trypan blue exclusion. Despite the simple and rapid nature of this assessment, concerns about the accuracy of these methods exist. Simple flow cytometry techniques which determine cell concentration and viability are available yet surprisingly have not been extensively used or validated with isolated hepatocyte preparations.

FcgammaRIIb expression on human germinal center B lymphocytes.

IgG antibody can specifically suppress the antibody response to antigen. This has been explained by the hypothesis that signaling through the B cell antigen receptor is negatively modulated by the co-ligation of immunoglobulin with the receptor for IgG, FcgammaRIIb. We hypothesized that inhibitory signaling through FcgammaRIIb would be counter-productive in germinal center cells undergoing selection by affinity maturation, since these cells are thought to receive a survival/proliferative signal by interacting with antigen displayed on follicular dendritic cells.