Dendritic cells in Leishmania infection

Dendritic cells (DCs) are key elements of the immune system, which function as sentinel in the periphery and alert T lymphocytes about the type of invading antigen and address their polarisation, in order to mount an efficacious immune response. Leishmania spp. are parasitic protozoa which may cause severe disease in humans and domestic animals. In this work, the main studies concerning the role of DCs in Leishmania infection are reviewed, in both the murine and human models. In particular, the importance of the genetic status of the hosts and of the different Leishmania species in modulating DC-mediated immune response is examined. In addition, different approaches of DC-based vaccination against experimental leishmaniasis, which could have important future applications, are summarised.     

Can metarhodopsin I activate rod outer segment phosphodiesterase?

The rod photoreceptors of vertebrate retinas contain a cGMP phosphodiesterase (PDE) that is activated by light. The light is absorbed by rhodopsin that activates an intermediate GTP-binding protein; this species then activates the PDE. Photo-excited rhodopsin passes through a series of transient states, and the purpose of this study is to identify the earliest state that interacts with the GTP-binding protein and thus activate the PDE. The majority of evidence points to this state being metarhodopsin II (MII), but PDE activation is seen at low temperatures where the rhodopsin reaction sequence is not expected to pass beyond the metarhodopsin I (MI) stage. Light thresholds for PDE activation have been determined under conditions where little MII is generated, and these are compared with the concentration of MII. The conclusion is that for a criterion threshold of PDE activity, the MII concentration is constant, irrespective of the amount of MI present, which suggests that MI cannot activate the PDE system.     

Statistical inference for net benefit measures in biomarker validation studies

Referral strategies based on risk scores and medical tests are commonly proposed. Direct assessment of their clinical utility requires implementing the strategy and is not possible in the early phases of biomarker research. Prior to late-phase studies, net benefit measures can be used to assess the potential clinical impact of a proposed strategy. Validation studies, in which the biomarker defines a prespecified referral strategy, are a gold standard approach to evaluating biomarker potential. Uncertainty, quantified by a confidence interval, is important to consider when deciding whether a biomarker warrants an impact study, does not demonstrate clinical potential, or that more data are needed. We establish distribution theory for empirical estimators of net benefit and propose empirical estimators of variance. The primary results are for the most commonly employed estimators of net benefit: from cohort and unmatched case-control samples, and for point estimates and net benefit curves. Novel estimators of net benefit under stratified two-phase and categorically matched case-control sampling are proposed and distribution theory developed. Results for common variants of net benefit and for estimation from right-censored outcomes are also presented. We motivate and demonstrate the methodology with examples from lung cancer research and highlight its application to study design.     

Antibody binding by native and denatured myosin and paramyosin.

By the techniques of immunodiffusion and fluorescent immunohistochemistry we show that antibodies to both the native and the SDS-denatured forms of the proteins, paramyosin and myosin, react with the native, SDS-denatured and glutaraldehyde-fixed forms of their respective antigens. Anti-denatured myosin also binds to both native and denatured forms of the proteolytic subfragments of myosin: globular subfragment-1 and alpha-helical LMM. Anti-native myosin, on the other hand, while able to bind to both native and denatured LMM or rod and to native and glutaraldehyde-fixed S-1, does not bind to SDS-denatured S-1.     

Comparison of cortisol-cortisone interconversion in vitro by the human and baboon placenta

The kinetics of 11 beta-hydroxysteroid dehydrogenase (11HSD) catalyzing the interconversion of cortisol (F) and cortisone (E) were compared in vitro following incubation of homogenates of human (N = 7) and baboon (N = 2) placenta. In both species, enzyme activity catalyzing the conversion of F to E was associated with the membrane fraction of the cell, was greater in the presence of NAD+ than NADP+, was of similar concentration within the placenta, and exhibited a similar Km for F. Moreover, there was no conversion of E to F in either the baboon or human placenta indicating that in both species, term placenta lacks the 11HSD enzyme catalyzing the reduction of the 11-oxo group of corticosteroids. Significantly, the conversion of F to E by both the baboon and human placenta was inhibited when progesterone was added to the reaction mixture at concentrations equimolar to the substrate. We conclude that 11HSD enzyme kinetics in term baboon placental homogenates are similar to those measured in human term placenta. Moreover, progesterone may be a physiologic regulator of 11HSD in both the human and baboon placenta. Collectively, our findings support the use of the baboon as a model for studies of the regulation of placental corticosteroid metabolism during human pregnancy.     

Gene transfer of immunoglobulin light chain restores heavy chain secretion

Several lines of evidence suggest that immunoglobulin (Ig) light (L) chain plays a role in the secretion of heavy (H) chain. For example, myeloma variant lines, which synthesize the Ig H chain but not the L chain, fail to secrete H chain protein. Here we have tested directly the role of chain assembly in the control of Ig secretion by the transfer of functional L chain genes into two such L chain-defective myeloma mutants. A lambda 2 or kappa L chain gene was introduced into variant lines of the mouse myelomas MOPC 315 (IgA, lambda 2) or PC7 (IgM, kappa), respectively. Although the two mutant lines are unable to secrete the H chain they produce, rescue of secretion of complete Ig protein molecules (IgA or IgM) was observed after transfection. These results imply that the secretory apparatus of these cells is intact and that the failure to secrete free H chain reflects a structural feature intrinsic to that protein. The implications of these results with respect to control of secretion of multi-subunit proteins are discussed.