HIV/SIV Infection Primes Monocytes and Dendritic Cells for Apoptosis

Subversion or exacerbation of antigen-presenting cells (APC) death modulates host/pathogen equilibrium. We demonstrated during in vitro differentiation of monocyte-derived macrophages and monocyte-derived dendritic cells (DCs) that HIV sensitizes the cells to undergo apoptosis in response to TRAIL and FasL, respectively. In addition, we found that HIV-1 increased the levels of pro-apoptotic Bax and Bak molecules and decreased the levels of anti-apoptotic Mcl-1 and FLIP proteins. To assess the relevance of these observations in the context of an experimental model of HIV infection, we investigated the death of APC during pathogenic SIV-infection in rhesus macaques (RMs). We demonstrated increased apoptosis, during the acute phase, of both peripheral blood DCs and monocytes (CD14+) from SIV+RMs, associated with a dysregulation in the balance of pro- and anti-apoptotic molecules. Caspase-inhibitor and death receptors antagonists prevented apoptosis of APCs from SIV+RMs. Furthermore, increased levels of FasL in the sera of pathogenic SIV+RMs were detected, compared to non-pathogenic SIV infection of African green monkey. We suggest that inappropriate apoptosis of antigen-presenting cells may contribute to dysregulation of cellular immunity early in the process of HIV/SIV infection

Temperature dependence of efficiency in GaInN/GaN light-emitting diodes with a GaInN underlayer

The temperature dependence of the efficiency (i.e., temperature-mediated efficiency droop) in blue light-emitting diodes (LEDs) is investigated. A GaInN/GaN LED with a GaInN underlayer having an indium mole fraction of 8% shows less temperature dependence of efficiency, compared to the LED without an underlayer. Better carrier confinement in the active region of the LED with a GaInN underlayer is proposed to reduce carrier leakage from the active region at high temperature. The results indicate that the insertion of an underlayer leads to an improvement of the LED's radiative efficiency and its high-temperature-tolerant performance.1110sciescopu