Synthesis and secretion of interferon by murine fibroblasts in response to intracellular Listeria monocytogenes

Listeria monocytogenes, a gram-positive facultative intracellular bacterium, was shown to be capable of infecting and proliferating in murine embryo fibroblasts. During exponential proliferation, the doubling time of the bacterium was determined to be 2.5 h intracellularly, compared with 25 min extracellularly. Progressive intracellular growth of listeriae ultimately resulted in the destruction of initially infected cells and the spread of infection to neighboring cells. Listeria infection induced fibroblasts to synthesize considerable quantities of an acid-stable interferon that proved to be antigenically indistinguishable from both polyinosinic-polycytidylic acid-induced and virus-induced interferon.