| Summary: | 碩士 === 國立中興大學 === 獸醫微生物學研究所 === 97 === The purposes of this study were to confirm that mouse interleukin-18s (small or short form of interleukin-18, IL-18s) possesses the activity in stimulating mouse immune cells to express IFN-γ gene, to compare the expression of IL-18 and IL-18s mRNAs in mouse organs, and to explore whether other mammals (in particular, human, sheep, and rabbit) also have similar IL-18 isoform.
Interleukin-18 (IL-18) is a multifunctional cytokine. In addition to stimulating the production of IFN-γ, IL-18 can also enhance cytotoxic activity of NK cells, and promote the differentiation of T cells. In recent ten years, researchers have identified a smaller isoform of IL-18 (IL-18s), which is resulted from alternatively spliced IL-18 mRNAs, in rainbow trout, rats, and mice.
In 2005, we and Yang et al. respectively cloned mouse IL-18s and expressed recombinant mouse IL-18s (rmIL-18s) protein. Yang et al. reported that rmIL-18s, unlike IL-18, could not stimulate mouse splenocytes to express IFN-γ. However, in our previous study, rmIL-18s expressed in our laboratory could stimulate mouse splenocytes to express
IFN-γ. In this study, we used rmIL-18 and rmIL-18s expressed in our laboratory to stimulate mouse splenocytes, respectively, and detected the expression of IFN-γ mRNA by reverse transcription-polymerase chain reaction (RT-PCR). Our results confirmed that rmIL-18s could induce mouse splenocytes to express IFN-γ with a comparable activity as recombinant mouse IL-18 (rmIL-18). Moreover, the rmIL-18s could stimulate EL-4 cells (derived from mouse T lymphoma) to express IFN-γ as well.
In addition, we detected and compared the expression of IL-18 and IL-18s mRNAs in mouse organs by RT-PCR. IL-18 mRNA was detected unanimously in all organs examined. However, the distribution of IL-18s mRNA in muse organs was variable among mice. In general, all mice expressed IL-18s mRNA in the muscle and gastrointestinal tract.
Furthermore, we extracted RNA from peripheral blood mononuclear cells (PBMCs) of human, sheep, and rabbit and explored the presence of IL-18s mRNA. We did not observe any alternatively spliced IL-18 mRNA in human and sheep. Interestingly, two alternatively spliced mRNAs of IL-18, which were not in-frame, were identified in rabbit. We expect that the two alternatively spliced IL-18 mRNAs can not produce functional proteins.
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