The role of these CPs in pathogenesis of and immunity to Mtb is unknown; however, CPs of other important bacteria such as Haemophilus influenzae type b, Streptococcus pneumoniae, Neisseria meningitidis and Salmonella typhi have been shown to inhibit complement-mediated and phagocytic actions, thereby preventing initial control of infection [7,8]. This evidence concerns the gene CAD and infection.