Comparative roles of macrophages and NK cells in the host innate resistance of mice to Mycobacterium fortuitum infection

Abstract Objectives . Profiles of host innate resistance to Mycobacterium fortuitum (MFT) infection in mice and the roles of macrophages (Mφs) and NK cells in host resistance to MFT infection were studied. Methods . MFT-infected mice with or without the treatments to reduce Mφs and NK cells were examined for survival and the bacterial loads in the kidneys during the course of infection. Results . A unique profile of strain difference was found in the innate resistance of mice to MFT. A/J, C3H/He and DBA/2 mice were susceptible, while BALB/c, B10A and C57BL/6 mice were resistant, in terms of survival after MFT infection. Such profiles of host resistance to MFT were essentially correlated with the ability of individual strain mice to prevent the bacterial growth in the early periods after infection. These profiles were different from the strain difference controlled by Bcg gene. Studies using carrageenan, anti-asialo GM1 antibody, and NK cell-deficient beige mice indicated the important roles of Mφs and NK cells in the host innate defense against MFT. Conclusions . These findings suggest that Bcg gene does not control the host resistance to MFT and that both Mφs and NK cells play crucial roles in the host innate resistance to MFT infection.