Phagocytes are the most probable source of this TNF-α response, and our studies showed that monocytes and neutrophils from normal dogs produce this cytokine in response to B. canis. The infection of phagocytes within explants may also explain why B. canis CFU increased in explants between 2 and 24 h p.i., whereas the bacterium did not replicate in primary canine trophoblasts in vitro during this time frame. Here, TNF is linked to infection.