Human CD1c+ dendritic cells secrete high levels of IL-12 and potently prime cytotoxic T-cell responses.

Dendritic cells (DC) have the unique capacities to induce primary T-cell responses. In mice, CD8α(+)DC are specialized to cross-prime CD8(+) T cells and produce interleukin-12 (IL-12) that promotes cytotoxicity. Human BDCA-3(+)DC share several relevant characteristics with CD8α(+)DC, but the capacities of human DC subsets to induce CD8(+) T-cell responses are incompletely understood. Here we compared CD1c(+) myeloid DC (mDC)1, BDCA-3(+)mDC2, and plasmacytoid DC (pDC) in peripheral blood and lymphoid tissues for phenotype, cytokine production, and their capacities to prime cytotoxic T cells. mDC1 were surprisingly the only human DC that secreted high amounts of IL-12p70, but they required combinational Toll-like receptor (TLR) stimulation. mDC2 and pDC produced interferon-λ and interferon-α, respectively. Importantly, mDC1 and mDC2 required different combinations of TLR ligands to cross-present protein antigens to CD8(+) T cells. pDC were inefficient and also expressed lower levels of major histocompatibility complex and co-stimulatory molecules. Nevertheless, all DC induced CD8(+) memory T-cell expansions upon licensing by CD4(+) T cells, and primed naive CD8(+) T cells following appropriate TLR stimulation. However, because mDC1 produced IL-12, they induced the highest levels of cytotoxic molecules. In conclusion, CD1c(+)mDC1 are the relevant source of IL-12 for naive T cells and are fully equipped to cross-prime cytotoxic T-cell responses.

Differential endothelial transcriptomics identifies semaphorin 3G as a vascular class 3 semaphorin.

OBJECTIVE: To characterize the role of a vascular-expressed class 3 semaphorin (semaphorin 3G [Sema3G]). METHODS AND RESULTS: Semaphorins have been identified as axon guidance molecules. Yet, they have more recently also been characterized as attractive and repulsive regulators of angiogenesis. Through a transcriptomic screen, we identified Sema3G as a molecule of angiogenic endothelial cells. Sema3G-deficient mice are viable and exhibit no overt vascular phenotype. Yet, LacZ expression in the Sema3G locus revealed intense arterial vascular staining in the angiogenic vasculature, starting at E9.5, which was detectable throughout adolescence and downregulated in adult vasculature. Sema3G is expressed as a full-length 100-kDa secreted molecule that is processed by furin proteases to yield 95- and a 65-kDa Sema domain-containing subunits. Full-length Sema3G binds to NP2, whereas processed Sema3G binds to NP1 and NP2. Expression profiling and cellular experiments identified autocrine effects of Sema3G on endothelial cells and paracrine effects on smooth muscle cells. CONCLUSIONS: Although the mouse knockout phenotype suggests compensatory mechanisms, the experiments identify Sema3G as a primarily endothelial cell-expressed class 3 semaphorin that controls endothelial and smooth muscle cell functions in autocrine and paracrine manners, respectively.

Evaluation of novel second-generation RSV and influenza rapid tests at the point of care.

Acute respiratory infections represent common pediatric emergencies. Infection control warrants immediate and accurate diagnoses. In the past, first-generation respiratory syncytial virus (RSV) rapid tests (strip tests) have shown suboptimal sensitivities. In 2013, the Food and Drug Administration licensed a second-generation RSV rapid test providing user-independent readouts (SOFIA™-RSV) using automated fluorescence assay technology known to yield superior results with influenza rapid testing. We are reporting the first point-of-care evaluation of the SOFIA™-RSV rapid test. In the Charité Influenza-Like Disease Cohort, 686 nasopharyngeal samples were tested in parallel with SOFIA™-RSV and SOFIA™-Influenza A+B. Compared to real-time PCR, SOFIA™-RSV sensitivities/specificities were 78.6%/93.9%, respectively (SOFIA™-Influenza A: 80.6%/99.3%). Performance was greatest in patients below 2 years of age with a test sensitivity of 81.8%. RSV sensitivities were highest (85%) in the first 2 days of illness and with nasopharyngeal compared to nasal swabs (P=0.055, McNemar's test). Second-generation RSV and influenza rapid testing provides highly accurate results facilitating timely patient cohortation and management.

CCR6 is expressed on an IL-10-producing, autoreactive memory T cell population with context-dependent regulatory function.

Interleukin (IL)-10 produced by regulatory T cell subsets is important for the prevention of autoimmunity and immunopathology, but little is known about the phenotype and function of IL-10-producing memory T cells. Human CD4(+)CCR6(+) memory T cells contained comparable numbers of IL-17- and IL-10-producing cells, and CCR6 was induced under both Th17-promoting conditions and upon tolerogenic T cell priming with transforming growth factor (TGF)-beta. In normal human spleens, the majority of CCR6(+) memory T cells were in the close vicinity of CCR6(+) myeloid dendritic cells (mDCs), and strikingly, some of them were secreting IL-10 in situ. Furthermore, CCR6(+) memory T cells produced suppressive IL-10 but not IL-2 upon stimulation with autologous immature mDCs ex vivo, and secreted IL-10 efficiently in response to suboptimal T cell receptor (TCR) stimulation with anti-CD3 antibodies. However, optimal TCR stimulation of CCR6(+) T cells induced expression of IL-2, interferon-gamma, CCL20, and CD40L, and autoreactive CCR6(+) T cell lines responded to various recall antigens. Notably, we isolated autoreactive CCR6(+) T cell clones with context-dependent behavior that produced IL-10 with autologous mDCs alone, but that secreted IL-2 and proliferated upon stimulation with tetanus toxoid. We propose the novel concept that a population of memory T cells, which is fully equipped to participate in secondary immune responses upon recognition of a relevant recall antigen, contributes to the maintenance of tolerance under steady-state conditions.