Systemic Listeria monocytogenes Infection as a Model to Study T Helper Cell Immune Responses

Listeria monocytogenes, a Gram-positive facultative intracellular pathogen, has been widely used as a model for studying the immune response. Here, we describe a protocol for the systemic infection of mice with L. monocytogenes, followed by isolation of lymphocytes from spleens and lymph nodes. We also include details on how to culture and store L. monocytogenes, as well as the specifics for fluorescence-activated cell sorting (FACS) for CD4⁺ cells in response to the systemic infection. This protocol can be adapted by changing the dosage of L. monocytogenes for a more or less aggressive infection and/or sorting for other immune cell subtypes of interest.