IL18 and infection: Previous studies have demonstrated IFNγ production at transcriptional and translational levels by various types of mouse and human macrophages [8] upon stimulation of IL12 and IL18 combination [6, 14, 33], IFNγ per se [17], U.V. exposure [66] or infections of Salmonella typhimurium [24, 38], Legionella pneumophila [52] and Chlamydia pneumoniae [21, 47–49, 55].