Brucella abortus is. an intracellular pathogen affecting macrophages. Macrophages release some antibrucella componen such as lysozymes (LZ), reactive-oxygen species (ROS) and reactive nitrite intermediates (RNI) which prevent intracellul survival of Brucella. The present study compared the antibrucella activity of bovine and murine macrophages followir stimulation with B. abortus lipopolysaccharides. Our results revealed increased production of these antibrucella substanci in murine macrophages as compared to bovine macrophages. The differential production of these antibrucella componen explained the differential B. abortus killing ability of these species (bovine and mice) that was measured in terms intramacrophagic survival of Brucellae in murine and bovine macrophages.