Differences in interleukin-12 and-15 production by dendritic cells at the early stage of Listeria monocytogenes infection between BALB/c and C57BL/6 mice

The mechanisms responsible for the resistance of C57BL/6 mice and for the s usceptibility of BALB/c mice to infection with Listeria monocytogenes were studied by comparing early IL-12 and IL-15 production by dendritic cells (D C) after infection with L. monocytogenes. Splenic DC expressing CD11b(low) and CD11c(+) obtained from C57BL/6 mice at 3 and 6 h after L. monocytogenes infection expressed higher levels of IL-12 p40 mRNA and IL-12 p40 protein than did those from BALB/c mice. Concurrently, a larger amount of IFN-gamma was produced by the splenic T cells from C57BL/6 mice in response to immob ilized anti-TCR alpha beta mAb than by those from BALB/c mice, while the sp lenic T cells from BALB/c mice produced a higher level of IL-4 upon TCR alp ha beta stimulation than did those of C57BL/6 mice. IL-15 mRNA and intracel lular IL-15 protein were detected more abundantly in the DC from C57BL/6 mi ce than in those from BALB/c mice on day 3 after infection. CD3(+) IL2R bet a(+) cells in the spleen were increased in C57BL/6 mice but not in BALB/c m ice at the early stage after infection. Furthermore, IL-12R beta 2 gene exp ression was up-regulated in T cells from C57BL/6 mice but not in those from BALB/c mice at the early stage after listerial infection. These results su ggest that the difference in early production of IL-12 and IL-15 by DC may at least partly underlie the difference in susceptibility to L. monocytogen es between C57BL/6 and BALB/c mice. (C) 2000 Academic Press.