Apoptosis in infectious disease: how bacteria interfere with the apoptotic apparatus

Cell death by apoptosis is a common response of a human cell to many extrinsic stimuli. A cell's sensitivity to apoptotic triggers is affected by its activation and differentiation status. Bacteria are recognised by cellular receptors and elicit a multitude of signal transduction events that can, among other effects, alter the cell's response towards apoptotic stimuli. Many different bacteria and bacterial products have been recognised as agents that can act in this way and either induce or inhibit cell death. Besides these common and, as we argue, indirect activities, chlamydiae have been described to have a more specific capacity. These specialists of intracellular life can directly attack the host cell's apoptotic pathway. Here, we will attempt to structure the field of bacterial inhibition of apoptosis and discuss recent advancements in our knowledge of how chlamydiae interfere with the host cell's capacity to undergo apoptosis.