Identification of IFN-gamma-producing cells in IL-12/IL-18-treated mice.
Both IL-12 and IL-18 have been characterized as effective IFN-gamma-inducing cytokines. Concomitant treatment with IL-12 and IL-18 has been shown to synergistically induce IFN-gamma and may be an effective therapy for treating cancer, allergy, and infectious diseases. To understand the mechanisms underlying the strong induction of IFN-gamma by IL-12/IL-18 in mice, we focused our studies on the IFN-gamma-producing cells in various lymphoid organs and tissues and utilized the intracellular cytokine staining method to detect such cells in situ. After combined treatment with IL-12 and IL-18, IFN-gamma-positive cells in C57BL/6 mice were detected in the liver (12.18%), spleen (0.68%), bone marrow (1.80%), and peritoneum (2.12%), but not in the thymus or lymph nodes (<0.05 and <0.08%, respectively). A two-color staining method revealed that the majority of IFN-gamma-producing cells in the liver were NK1.1(+) cells, while those in the spleen were mostly CD3(+) cells, and to a lesser degree NK1.1(+) cells. Both CD4(+) and CD8(+) cells in the liver and in the spleen produced IFN-gamma. The CD19(+) B cell population was not definitely shown to produce IFN-gamma in our induction experiments. NKT cells, which are a subpopulation of NK1. 1(+) CD3(+) cells, were diminished in the liver and did not seem to contribute to IFN-gamma production arising from IL-12/IL-18 treatment. Further in vitro experiments confirmed the responsiveness of hepatic mononuclear cells to IL-12/IL-18 stimulation. This study is the first to show the IFN-gamma-producing mechanisms of IL-12/IL-18 treatment at the phenotypic level.
Otani
T
T
Fujisaki Cell Center, Hayashibara Biochemical Laboratories, Inc., Okayama, Japan.
Nakamura
S
S
Toki
M
M
Motoda
R
R
Kurimoto
M
M
Orita
K
K
D000818:Animals; D004357:Drug Synergism; D005260:Female; D005434:Flow Cytometry; D007371:Interferon-gamma / Q000096:biosynthesis*; D018664:Interleukin-12 / Q000494:pharmacology*; D020382:Interleukin-18 / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000276:immunology; D008099:Liver / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL
D020382:Interleukin-18; D018664:Interleukin-12; D007371:Interferon-gamma