Differential Susceptibility of Human Peripheral Blood T Cells to Suppression by Environmental Levels of Sodium Arsenite and Monomethylarsonous Acid

Human exposure to arsenic in drinking water is known to contribute to many different health outcomes such as cancer, diabetes, and cardiopulmonary disease. Several epidemiological studies suggest that T cell function is also altered by drinking water arsenic exposure. However, it is unclear how individual responses differ to various levels of exposure to arsenic. Our laboratory has recently identified differential responses of human peripheral blood mononuclear cell (HPMBC) T cells as measured by polyclonal T cell activation by mitogens during sodium arsenite exposure. T cells from certain healthy individuals exposed to various concentrations (1–100 nM) of arsenite in vitro showed a dose-dependent suppression at these extremely low concentrations (∼0.1–10 ppb) of arsenite, whereas other individuals were not suppressed at low concentrations. In a series of more than 30 normal donors, two individuals were found to be sensitive to low concentration (10 nM equivalent ∼1 ppb drinking water exposure) to sodium arsenite-induced inhibition of T cell proliferation produced by phytohemagglutinin (PHA) and anti-CD3/anti-CD28. In an arsenite-susceptible individual, arsenite suppressed the activation of Th1 (Tbet) cells, and decreased the percentage of cells in the double positive Th17 (RORγt) and Treg (FoxP3) population. While the majority of normal blood donors tested were not susceptible to inhibition of proliferation at the 1–100 nM concentrations of As+3, it was found that all donors were sensitive to suppression by 100 nM monomethylarsonous acid (MMA+3), a key metabolite of arsenite. Thus, our studies demonstrate for the first time that low ppb-equivalent concentrations of As+3 are immunosuppressive to HPBMC T cells in some individuals, but that most donor HPBMC are sensitive to suppression by MMA+3 at environmentally relevant exposure levels

High-resolution radio astronomy: An outlook for Africa

Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the current IAU Symposium, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Network (EVN), which operates under the "open sky"policy via peer-reviewed observing proposals. Recent EVN observations cover a broad range of science themes from high-sensitivity monitoring of structural changes in inner AGN areas to observations of tidal eruptions in AGN cores and investigation of redshift-dependent properties of parsec-scale radio structures of AGN. All the topics above should be considered as potentially rewarding scientific activities of the prospective African VLBI Network (AVN), a natural "scientific ally"of EVN. This contribution briefly describe the status and near-term strategy for the AVN development as a southern extension of the EVN-AVN alliance and as an eventual bridge to the Square Kilometre Array (SKA) with its mid-frequency core in South Africa.</p

High-resolution radio astronomy: An outlook for Africa

Very Long Baseline Interferometry (VLBI) offers unrivalled resolution in studies of celestial radio sources. The subjects of interest of the current IAU Symposium, the Active Galactic Nuclei (AGN) of all types, constitute the major observing sample of modern VLBI networks. At present, the largest in the world in terms of the number of telescopes and geographical coverage is the European VLBI Network (EVN), which operates under the "open sky"policy via peer-reviewed observing proposals. Recent EVN observations cover a broad range of science themes from high-sensitivity monitoring of structural changes in inner AGN areas to observations of tidal eruptions in AGN cores and investigation of redshift-dependent properties of parsec-scale radio structures of AGN. All the topics above should be considered as potentially rewarding scientific activities of the prospective African VLBI Network (AVN), a natural "scientific ally"of EVN. This contribution briefly describe the status and near-term strategy for the AVN development as a southern extension of the EVN-AVN alliance and as an eventual bridge to the Square Kilometre Array (SKA) with its mid-frequency core in South Africa.Astrodynamics & Space Mission

PHA-Induced³H-Thymidine Stimulation and Urinary Arsenic (Inorganic + Organic) in Normal Human Blood Donors.

<p>Note: AsB = arseno betaine, MMA⁺⁵ and DMA⁺⁵ also include MMA⁺³ and DMA⁺³.</p><p>PHA-Induced³H-Thymidine Stimulation and Urinary Arsenic (Inorganic + Organic) in Normal Human Blood Donors.</p

Arsenite Suppresses Anti-CD3/Anti-CD28 Naïve HPBMC T cell Differentiation.

<p>Note: DP = double positive; Values shown are the Mean ± SD with *indicating statistical significance at p<.05.</p><p>Arsenite Suppresses Anti-CD3/Anti-CD28 Naïve HPBMC T cell Differentiation.</p

Evaluation of As⁺³ inhibition of HPBMC proliferation.

<p>In panel A, the typical response of 15 donors is shown where there is no inhibition of PHA-induced T cell proliferation. In panel B, 2 donors are shown that were extremely sensitive to low dose (0.1–1 nM) inhibition of the PHA response. Data shown are the Mean ± SD with *p<.05.</p

Correlation analysis of MMA in urine with PHA-induced T cell stimulation (³H-Thymidine counts per minute (CPM).

<p>There is an indication of a weak correlation between urinary MMA (combined MMA⁺³ and MMA⁺⁵) amounts and CPM in the 13 donors analyzed. Values are log transformed. R = −0.46, p = 0.24.</p