マウスMycobacterium intracellulare感染におけるサイトカイン産生動態と抵抗性

Abstract

The purpose of this study was to better the sequence of cytokine mRNA expression during the infectious course of Mycobacterium intracellulare, belonging to Mycobacterium avium complex (MAC), in MAC-resistant A/J mice and MAC-susceptible C57 BL/6 mice. Cytokine mRNA expression was detected by polymerase chain reaction-assisted amplification of RNA extracted from the spleen cells of individual mice euthanized on days 0 to 40 of infection. By using this method, mRNAs for IL-2, IL-3, IL-5, IFN-α and IFN-β were not detected in RNA from the spleen cells of infected mice of both strains over the infection period. Expression of mRNAs for IL-1, IL-6, TNF-α and IFN-γ remained similar in intensity and timing between both mouse strains during infection. The mRNA for IL-4 was expressed in RNA from C57 BL/6 spleen cells after day 9, at the time when the number of viable M.intracellulare began increasing in the spleen of C57 BL/6 mice, while IL-4 mRNA was not induced in A/J spleen cells throughout the infectious course. Moreover, mRNA for IL-10 was expressed in C57 BL/6 mice at higher levels than that in A/J mice after day 6 of infection. Recombinant IL-4 and IL-10 affected anti-MAC activity of spleen cells from MAC-infected A/J mice in vitro, and also recombinant IL-4 suppressed the in vitro production of IFN-γ by infected A/J spleen cells upon stimulation with M.intracellulare extract. These results suggest that the induction of inhibitory cytokines, including IL-4 and IL-10, after MAC infection results in deterioration of mouse innate resistance to MAC infection.