Lymphocyte apoptosis as an immune subversion strategy of microbial pathogens.

Apoptosis is a component of cellular death in several immunological reactions. Lymphocyte apoptosis is a feature of negative selection of thymic lymphocytes. Target cells die by apoptosis during their interaction with cytotoxic T cells. Antigens derived from apoptotic cells can be cross-presented by antigen presenting cells (APCs). In these examples, apoptotic death is a beneficial feature for the individual. The apoptosis of cells also occurs during infection with a variety of microorganisms, but this process can be detrimental to the handling of the infection by the host. Here, we aim to highlight some of the recent advances in understanding why apoptosis can be a detrimental event during infection. We will focus on recent research with the intracellular bacterial pathogen Listeria monocytogenes, which demonstrates how apoptosis is induced, some of the host pathways that are exploited and the immunological consequences of cell death. We propose that L. monocytogenes causes lymphocyte death by enhancing the cell-death programs of the host. The presence of apoptotic lymphocytes downregulates early innate immunity, creating a permissive environment for bacterial growth.