Identification of IFN-gamma-producing cells in IL-12/IL-18-treated mice

Area of Science:

• Immunology
• Cytokine Signaling
• Innate Immunity

Background:

• Interleukin-12 (IL-12) and Interleukin-18 (IL-18) are key cytokines known for inducing interferon-gamma (IFN-γ).
• Concomitant administration of IL-12 and IL-18 exhibits synergistic IFN-γ induction, suggesting potential therapeutic applications in cancer, allergy, and infectious diseases.
• Understanding the cellular sources of IFN-γ is crucial for elucidating the mechanisms behind IL-12/IL-18 synergy.

Purpose of the Study:

• To investigate the cellular mechanisms underlying robust IFN-γ production induced by combined IL-12 and IL-18 treatment in mice.
• To identify and characterize the specific immune cell populations responsible for IFN-γ production in various lymphoid organs and tissues following IL-12/IL-18 stimulation.

Main Methods:

• Utilized intracellular cytokine staining for in situ detection of IFN-γ-producing cells in C57BL/6 mice.
• Analyzed IFN-γ-positive cell populations in the liver, spleen, bone marrow, peritoneum, thymus, and lymph nodes.
• Employed two-color staining to identify cell surface markers (e.g., NK1.1, CD3, CD4, CD8, CD19) on IFN-γ-producing cells.
• Conducted in vitro experiments to confirm the responsiveness of hepatic mononuclear cells to IL-12/IL-18 stimulation.

Main Results:

• Significant IFN-γ-positive cells were detected in the liver (12.18%), spleen (0.68%), bone marrow (1.80%), and peritoneum (2.12%) after IL-12/IL-18 treatment.
• The majority of IFN-γ-producing cells in the liver were NK1.1(+) cells, while splenic IFN-γ producers were predominantly CD3(+) T cells, with a smaller contribution from NK1.1(+) cells.
• Both CD4(+) and CD8(+) T cells in the liver and spleen produced IFN-γ. NKT cells were diminished and did not appear to contribute significantly.
• Hepatic mononuclear cells demonstrated responsiveness to IL-12/IL-18 stimulation in vitro.

Conclusions:

• This study provides the first phenotypic characterization of IFN-γ-producing cells following combined IL-12 and IL-18 treatment.
• The findings highlight the liver and spleen as major sites of IL-12/IL-18-induced IFN-γ production, mediated primarily by NK1.1(+) cells and CD3(+) T cells, respectively.
• The results offer insights into the cellular mechanisms driving the synergistic IFN-γ response, informing potential immunotherapies.