Members of the Mycobacterium tuberculosis complex share a high level of genetic identity, however pathogenic ability appears to display host restriction. Interestingly M. tuberculosis, the primary cause of tuberculosis in humans, is non-pathogenic in cattle. Conversely Mycobacterium bovis, the cause of tuberculosis in cattle, is also responsible for a proportion of tuberculosis cases in humans. We hypothesise that differences in the abilities of M. bovis and M. tuberculosis to cause pathogenesis in cattle will be reflected in their interactions with bovine antigen presenting cells. To analyse the importance of host species in mycobacterial infection, bovine antigen presenting cells were infected with bovine or human mycobacterial strains. Levels of nitric oxide and tumour necrosis factor production, markers of antimicrobial activity, were found to be associated with a specific mycobacterial strain, and varied between cell subsets.