Use of bone marrow-derived macrophages to model murine innate immune responses

The innate immune system is composed of neutrophils and monocyte/macrophages. As a cell type, bone marrow-derived macrophage (BMM) are easier to study than neutrophils since they are still capable of cell division and have a longer life span. However, in comparison with neutrophils, few methodological studies on the production of reactive oxygen species (ROS) by such macrophages have been reported. Here we present studies on ROS production of this cell type under various conditions including the use of different priming and stimulating agents. In addition, we report that the de novo adhesion of BMM to tissue culture plates induces superoxide anion production and this can be further enhanced by stimulation with PMA. BMM are able to adhere to endothelial cells that have been activated by TNF-α exposure, and under these circumstances also generate ROS. We explored different methods to introduce gene products into BMM without activating them to avoid complicating subsequent studies of ROS production. Infection with lentiviral vectors was very efficient, allowed long-term expression and did not activate the BMM. We conclude that BMM are very suitable for the biochemical study of the oxidative burst.