%A Ebenezer GJ %A Arumugam S %A Job CK %T Dosage and site of entry influence growth and dissemination of Mycobacterium leprae in T900r mice %0 Journal Article %D 2002 %J International Journal of Leprosy and other Mycobacterial Diseases %P 0148-916X %V 70 %N 4 %X In the present study, we examined profiles of the interaction of Mycobacterium leprae and Mycobacterium avium complex (MAC) with murine peritoneal macrophages (MΦS) in terms of up-regulation of MΦ expression of proinflammatory and im-munosuppressing cytolines (CKs) after infection. First, the reverse transcription polymerase chain reaction (RT-PCR) assay revealed that both MAC and M. leprae infections up-regulated MΦ mRNA expression IL-12. TNF-α, IL-10, and transforming growth factor-β (TGF-β). except that M. leprae-infected MΦs showed no increase in the IL-12 mRNA expression. Second, the RT-PCR assay also showed some differences between M. leprae- and MAC-infected MΦs with respect to the modes of IL-10 and inducible nitric oxide synthase (iNOS) mRNA expression. That is MAC, but not M. leprae, infection caused a prolonged increase in the expression of IL-10 and iNOS mRNAs. Third, a ribonuclease protection assay revealed that MΦs co-infected with MAC and M. leprae showed the IL-12. TNF-α and IL-10 mRNA expression in an intermediate mode of those of MΦs infected with either M. leprae or MAC alone. This implies that the CK expression of M. leprae-infected MΦs may be modified by co-infection with MAC. These findings may suggest differential interactions of M. leprae and MAC organisms with murine peritoneal MΦs in terms of the activation of signal transduction pathways for expression of some kinds of im-munoregulatory cytokines and immuno-protective enzymes.