ABSTRACT
Cross-talk between TGF-beta and IL-6 has been shown to direct the differentiation of CD4(+) cells into special IL-17-secreting cells, which are termed Th17 cells. In this study, we demonstrated that TGF-beta and IL-6 could stimulate CD8(+) cells to differentiate into noncytotoxic, IL-17-producing cells in MLC. These IL-17-producing CD8(+) cells exhibit a unique granzyme B(-)IFN-gamma(-)IL-10(-) phenotype. The mRNA level of Th2/T cytotoxic 2 (Tc2) transcription factors GATA3 and Th1/Tc1 transcription factors T-box expressed in T cell (T-bet) as well as its target H2.O-like homeobox (Hlx) is decreased in CD8(+) cells from TGF-beta- and IL-6-treated MLC. In addition, these CD8(+) cells display a marked up-regulation of retinoic acid-related orphan receptor-gammat, a key IL-17 transcription factor. These results demonstrate that the existence of an IL-17-producing CD8(+) subset belongs to neither the Tc1 nor the Tc2 subset and can be categorized as a T noncytotoxic 17 (Tnc17) subset.
Subject(s)
CD8 Antigens/analysis , CD8-Positive T-Lymphocytes/immunology , Interleukin-6/pharmacology , Transforming Growth Factor beta/pharmacology , Animals , CD8-Positive T-Lymphocytes/metabolism , Cell Line, Tumor , Cells, Cultured , Female , Interleukin-17/metabolism , Interleukin-6/immunology , Lymphocyte Culture Test, Mixed , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , RNA, Messenger/metabolism , T-Lymphocytes, Cytotoxic/immunology , Th1 Cells/immunologyABSTRACT
Though it is well established that gamma interferon (IFN-gamma) is crucial to the early innate defense of murine listeriosis, its sources remain controversial. In this study, intracellular cytokine staining of IFN-gamma-expressing splenocytes early after Listeria monocytogenes infection revealed that NK1.1(+), CD11c(+), CD8(+) T, and CD4(+) T cells expressed IFN-gamma 24 h after infection. Contrary to the previous report, most IFN-gamma(+) dendritic cells (DC) were CD8alpha(-) DC. Unexpectedly, almost all CD11c(+) IFN-gamma-expressing cells also expressed NK1.1. These NK1.1(+) CD11c(+) cells represented primary IFN-gamma-expressing cells after infection. In situ studies showed these NK1.1(+) CD11c(+) cells were recruited to the borders of infectious foci and expressed IFN-gamma. A significant NK1.1(+) CD11c(+) population was found in uninfected spleen, lymph node, blood, and bone marrow cells. And its number increased significantly in spleen, lymph node, and bone marrow after L. monocytogenes infection. Using interleukin-12 (IL-12) p40(-/-) mice, IFN-gamma expression was found to be largely IL-12 p40 dependent, and the number of IFN-gamma-expressing cells was only about one-third of that of wild-type mice. Moreover, the IFN-gamma expression was absolutely dependent on live L. monocytogenes infection, as no IFN-gamma was detected after inoculation of heat-killed L. monocytogenes. Our findings not only provide an insight into IFN-gamma expression after in vivo infection but may also change the current perceptions of DC and natural killer cells.
