TNF and retinal degeneration: The present study suggests a neurotoxic role of NF-κB in photoreceptor apoptosis by not only showing its persistent high expression levels in rd retinas spanning from P12 to P18 when the photoreceptor cell loss took place, but also revealing its activation in microglial cells and co-occurrence of increased TNF-α production in microglial cells in a typical period (from P12 to P14) of retinal degenerations of rd mice [6].