Blood monocytes: distinct subsets, how they relate to dendritic cells, and their possible roles in the regulation of T-cell responses

Monocytes can have important effects on the polarization and expansion of lymphocytes and may contribute to shaping primary and memory T-cell responses in humans and mice. However, their precise contribution in terms of cellular subsets and the molecular mechanisms involved remains to be determined. Mouse monocytes originate from a bone marrow progenitor, the macrophage and DC precursor (MDP), which also gives rise to conventional dendritic cells through a separate differentiation pathway. Mouse monocytes may be grouped in different functional subsets. The CD115(+) Gr1(+) 'inflammatory' monocyte subset can give rise not only to immunostimulatory 'TipDCs' in infected mice but also to immunosuppressive 'myeloid-derived suppressor cells' in tumor-bearing mice. CD115(+) Gr1(+) monocytes can also contribute to the renewal of several resident subsets of macrophages and DCs, such as microglia and Langerhans cells, in inflammatory conditions. The CD115(+) Gr1(-) 'resident' monocyte subset patrols blood vessels in the steady state and extravasates during infection with Listeria monocytogenes or in the healing myocardium. CD115(+) Gr1(-) monocytes are responsible for an early and transient inflammatory burst during Lm infection, which may play a role in the recruitment of other effector cells and subsequently differentiate toward 'M2'-like macrophages that may be involved in wound healing. More research will no doubt confirm the existence of more functional subsets, the developmental relationship between mouse subsets as well as the correspondence between mouse subsets and human subsets of monocytes. We will discuss here the potential roles of monocytes in the immune response, the existence of functional subsets and their relationship with other myeloid cells, including dendritic cells.     

Cytology and outcome of LSIL: cannot exclude HSIL compared to ASC-H

Objective:  The cytological features associated with clinical outcome of 'LSIL cannot exclude HSIL (LSIL-H)' in comparison with 'atypical squamous cells cannot exclude HSIL (ASC-H)' are incompletely described.
Methods:  LSIL-H and ASC-H Pap tests reported in a regional laboratory during a 13-month period were reviewed by two pathologists. Cytological features suspicious for HSIL were evaluated against a check list of 52 atypical features. All histology over 2 years of follow up for tests reclassified as LSIL-H and ASC-H was retrieved to determine clinical outcome. Atypical cytological features were correlated with outcome.
Results:  The review yielded 89 LSIL-H and 86 ASC-H. The highest ranked atypical cytological feature in each group was increased nuclear cytoplasmic ratio. Clinical outcome was positive (CIN II/III or AIS) in 44 (49%) LSIL-H and 33 (38%) ASC-H. Round ( P  = 0.02) and naked nuclei ( P  = 0.009) were significant correlates of outcome amongst LSIL-H tests, but no feature correlated with outcome in the ASC-H group.
Conclusions:  LSIL-H is different to ASC-H because of the 11% higher frequency of a positive outcome and the cytological features associated with outcome.     

Plasma-based approach to measure target engagement for liver-targeting stearoyl-CoA desaturase 1 inhibitors

A positive correlation between stearoyl-CoA desaturase (SCD)1 expression and metabolic diseases has been reported in rodents and humans. These findings indicate that SCD1 is a promising therapeutic target for the chronic treatment of diabetes and dyslipidemia. The SCD1 enzyme is expressed at high levels in several human tissues and is required for the biosynthesis of monounsaturated fatty acids, which are involved in many biological processes. Liver-targeted SCD inhibitors were designed to pharmacologically manipulate SCD1 activity in the liver to avoid adverse events due to systemic inhibition. This article describes the development of a plasma-based SCD assay to assess the level of SCD inhibition, which is defined in this article as target engagement. Essentially, animals are dosed with an exogenous deuterated tracer (d7-stearic acid) as substrate, and the converted d7-oleic acid product is measured to monitor SCD1 inhibition. This study reveals that this plasma-based assay correlates with liver SCD1 inhibition and can thus have clinical utility.     

Influenza A Virus Assembly Intermediates Fuse in the Cytoplasm

Reassortment of influenza viral RNA (vRNA) segments in co-infected cells can lead to the emergence of viruses with pandemic potential. Replication of influenza vRNA occurs in the nucleus of infected cells, while progeny virions bud from the plasma membrane. However, the intracellular mechanics of vRNA assembly into progeny virions is not well understood. Here we used recent advances in microscopy to explore vRNA assembly and transport during a productive infection. We visualized four distinct vRNA segments within a single cell using fluorescent in situ hybridization (FISH) and observed that foci containing more than one vRNA segment were found at the external nuclear periphery, suggesting that vRNA segments are not exported to the cytoplasm individually. Although many cytoplasmic foci contain multiple vRNA segments, not all vRNA species are present in every focus, indicating that assembly of all eight vRNA segments does not occur prior to export from the nucleus. To extend the observations made in fixed cells, we used a virus that encodes GFP fused to the viral polymerase acidic (PA) protein (WSN PA-GFP) to explore the dynamics of vRNA assembly in live cells during a productive infection. Since WSN PA-GFP colocalizes with viral nucleoprotein and influenza vRNA segments, we used it as a surrogate for visualizing vRNA transport in 3D and at high speed by inverted selective-plane illumination microscopy. We observed cytoplasmic PA-GFP foci colocalizing and traveling together en route to the plasma membrane. Our data strongly support a model in which vRNA segments are exported from the nucleus as complexes that assemble en route to the plasma membrane through dynamic colocalization events in the cytoplasm.     

In Vivo Measurement of Hippocampal GABAA/cBZR Density with [18F]-Flumazenil PET for the Study of Disease Progression in an Animal Model of Temporal Lobe Epilepsy

Purpose

Imbalance of inhibitory GABAergic neurotransmission has been proposed to play a role in the pathogenesis of temporal lobe epilepsy (TLE). This study aimed to investigate whether [¹⁸F]-flumazenil ([¹⁸F]-FMZ) PET could be used to non-invasively characterise GABA_A/central benzodiazepine receptor (GABA_A/cBZR) density and affinity in vivo in the post-kainic acid status epilepticus (SE) model of TLE.

Methods

Dynamic [¹⁸F]-FMZ -PET scans using a multi-injection protocol were acquired in four male wistar rats for validation of the partial saturation model (PSM). SE was induced in eight male Wistar rats (10 weeks of age) by i.p. injection of kainic acid (7.5–25 mg/kg), while control rats (n = 7) received saline injections. Five weeks post-SE, an anatomic MRI scan was acquired and the following week an [¹⁸F]-FMZ PET scan (3.6–4.6 nmol). The PET data was co-registered to the MRI and regions of interest drawn on the MRI for selected structures. A PSM was used to derive receptor density and apparent affinity from the [¹⁸F]-FMZ PET data.

Key Findings

The PSM was found to adequately model [¹⁸F]-FMZ binding in vivo. There was a significant decrease in hippocampal receptor density in the SE group (p<0.01), accompanied by an increase in apparent affinity (p<0.05) compared to controls. No change in cortical receptor binding was observed. Hippocampal volume reduction and cell loss was only seen in a subset of animals. Histological assessment of hippocampal cell loss was significantly correlated with hippocampal volume measured by MRI (p<0.05), but did not correlate with [¹⁸F]-FMZ binding.

Significance

Alterations to hippocampal GABA_A/cBZR density and affinity in the post-kainic acid SE model of TLE are detectable in vivo with [¹⁸F]-FMZ PET and a PSM. These changes are independent from hippocampal cell and volume loss. [¹⁸F]-FMZ PET is useful for investigating the role that changes GABA_A/cBZR density and binding affinity play in the pathogenesis of TLE.