TNF and infection: The demonstrated effects on the mouse neuron of a R. helvetica infection, differ to some extent from previously reported findings in infection of human monocytes with R. helvetica, where TNFα production was induced and the rickettsia bacteria both replicated and survived in the monocyte’s cell plasma without causing apoptosis of the host cell, which instead theoretically enables the infection to also spread to the CNS by crossing the blood-brain barrier [6, 14].