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An activation-induced IL-15 isoform is a natural antagonist for IL-15 function.

Zhao L, Hu B, Zhang Y, Song Y, Lin D, Liu Y, Mei Y, Sandikin D, Sun W, Zhuang M, Liu H - Sci Rep (2016)

Bottom Line: Here we identified an IL-15 isoform lacking exon-6, IL-15ΔE6, generated by alternative splicing events of activated immune cells, including macrophages and B cells.Furthermore, flow cytometry analysis demonstrated that IL-15ΔE6 expression reduced the percentages of inflammatory T cells in the spleen and spinal cord, and inhibited the infiltration of macrophages to the CNS.Our results demonstrated that IL-15ΔE6 could be induced during immune activation and function as a negative feedback mechanism to dampen IL-15-mediated inflammatory events.

View Article: PubMed Central - PubMed

Affiliation: Institute of Blood and Marrow Transplantation, Cyrus Tang Hematology Center, Department of Hematology, Collaborative Innovation Center of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, P. R. China.

ABSTRACT
Interleukin 15 (IL-15) expression induces the secretion of inflammatory cytokines, inhibits the apoptosis of activated T cells and prolongs the survival of CD8(+) memory T cells. Here we identified an IL-15 isoform lacking exon-6, IL-15ΔE6, generated by alternative splicing events of activated immune cells, including macrophages and B cells. In vitro study showed that IL-15ΔE6 could antagonize IL-15-mediated T cell proliferation. The receptor binding assay revealed that IL-15ΔE6 could bind to IL-15Rα and interfere with the binding between IL-15 and IL-15Rα. Over-expression of IL-15ΔE6 in the murine EAE model ameliorated the EAE symptoms of the mice. The clinical scores were significantly lower in the mice expressing IL-15ΔE6 than the control mice and the mice expressing IL-15. The inflammation and demyelination of the EAE mice expressing IL-15ΔE6 were less severe than the control group. Furthermore, flow cytometry analysis demonstrated that IL-15ΔE6 expression reduced the percentages of inflammatory T cells in the spleen and spinal cord, and inhibited the infiltration of macrophages to the CNS. Our results demonstrated that IL-15ΔE6 could be induced during immune activation and function as a negative feedback mechanism to dampen IL-15-mediated inflammatory events.

No MeSH data available.


Related in: MedlinePlus

Murine exon-6-lacking-IL-15 isoform was generated by alternative splicing in activated immune cells.(a) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA extracted from the splenocytes was reverse transcribed into cDNA and amplified by PCR using a specific primer for coding sequences of murine IL-15 cDNA. (b) Coding sequence comparison between IL-15ΔE6 isoform and IL-15. Boxes represent exons and the dashed lines indicate the consequence of alternative splicing. (c) Primary B cells, macrophages, SP2/0 cell line and Raw 246.7 cell line were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA was extracted from these cells and reverse transcribed into cDNA and amplified by PCR. (d) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. During LPS stimulation, CHX (1 μg/ml) was added for the last 12 h of culture. The cellular lysates were blotted with rabbit anti-mouse-IL-15 polyclonal Ab followed by goat- anti-rabbit IgG Ab. The data shown represent at least three independent experiments.
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f1: Murine exon-6-lacking-IL-15 isoform was generated by alternative splicing in activated immune cells.(a) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA extracted from the splenocytes was reverse transcribed into cDNA and amplified by PCR using a specific primer for coding sequences of murine IL-15 cDNA. (b) Coding sequence comparison between IL-15ΔE6 isoform and IL-15. Boxes represent exons and the dashed lines indicate the consequence of alternative splicing. (c) Primary B cells, macrophages, SP2/0 cell line and Raw 246.7 cell line were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA was extracted from these cells and reverse transcribed into cDNA and amplified by PCR. (d) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. During LPS stimulation, CHX (1 μg/ml) was added for the last 12 h of culture. The cellular lysates were blotted with rabbit anti-mouse-IL-15 polyclonal Ab followed by goat- anti-rabbit IgG Ab. The data shown represent at least three independent experiments.

Mentions: It was reported that the level of IL-15 transcription was increased in the immune cells after stimulation with LPS2448. Interestingly, we observed a smaller product of IL-15 from RT-PCR reaction using specific primers for IL-15 and the cDNA from splenocytes stimulated with LPS for 24 h (Fig. 1a). This smaller product was not present in the unstimulated splenocytes. The smaller PCR products were sequenced and proved to be the exon-6-missing IL-15 isoform (Fig. 1b).


An activation-induced IL-15 isoform is a natural antagonist for IL-15 function.

Zhao L, Hu B, Zhang Y, Song Y, Lin D, Liu Y, Mei Y, Sandikin D, Sun W, Zhuang M, Liu H - Sci Rep (2016)

Murine exon-6-lacking-IL-15 isoform was generated by alternative splicing in activated immune cells.(a) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA extracted from the splenocytes was reverse transcribed into cDNA and amplified by PCR using a specific primer for coding sequences of murine IL-15 cDNA. (b) Coding sequence comparison between IL-15ΔE6 isoform and IL-15. Boxes represent exons and the dashed lines indicate the consequence of alternative splicing. (c) Primary B cells, macrophages, SP2/0 cell line and Raw 246.7 cell line were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA was extracted from these cells and reverse transcribed into cDNA and amplified by PCR. (d) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. During LPS stimulation, CHX (1 μg/ml) was added for the last 12 h of culture. The cellular lysates were blotted with rabbit anti-mouse-IL-15 polyclonal Ab followed by goat- anti-rabbit IgG Ab. The data shown represent at least three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4863161&req=5

f1: Murine exon-6-lacking-IL-15 isoform was generated by alternative splicing in activated immune cells.(a) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA extracted from the splenocytes was reverse transcribed into cDNA and amplified by PCR using a specific primer for coding sequences of murine IL-15 cDNA. (b) Coding sequence comparison between IL-15ΔE6 isoform and IL-15. Boxes represent exons and the dashed lines indicate the consequence of alternative splicing. (c) Primary B cells, macrophages, SP2/0 cell line and Raw 246.7 cell line were cultured with or without LPS (10 μg/ml) for 24 h. Total RNA was extracted from these cells and reverse transcribed into cDNA and amplified by PCR. (d) Splenocytes were cultured with or without LPS (10 μg/ml) for 24 h. During LPS stimulation, CHX (1 μg/ml) was added for the last 12 h of culture. The cellular lysates were blotted with rabbit anti-mouse-IL-15 polyclonal Ab followed by goat- anti-rabbit IgG Ab. The data shown represent at least three independent experiments.
Mentions: It was reported that the level of IL-15 transcription was increased in the immune cells after stimulation with LPS2448. Interestingly, we observed a smaller product of IL-15 from RT-PCR reaction using specific primers for IL-15 and the cDNA from splenocytes stimulated with LPS for 24 h (Fig. 1a). This smaller product was not present in the unstimulated splenocytes. The smaller PCR products were sequenced and proved to be the exon-6-missing IL-15 isoform (Fig. 1b).

Bottom Line: Here we identified an IL-15 isoform lacking exon-6, IL-15ΔE6, generated by alternative splicing events of activated immune cells, including macrophages and B cells.Furthermore, flow cytometry analysis demonstrated that IL-15ΔE6 expression reduced the percentages of inflammatory T cells in the spleen and spinal cord, and inhibited the infiltration of macrophages to the CNS.Our results demonstrated that IL-15ΔE6 could be induced during immune activation and function as a negative feedback mechanism to dampen IL-15-mediated inflammatory events.

View Article: PubMed Central - PubMed

Affiliation: Institute of Blood and Marrow Transplantation, Cyrus Tang Hematology Center, Department of Hematology, Collaborative Innovation Center of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, P. R. China.

ABSTRACT
Interleukin 15 (IL-15) expression induces the secretion of inflammatory cytokines, inhibits the apoptosis of activated T cells and prolongs the survival of CD8(+) memory T cells. Here we identified an IL-15 isoform lacking exon-6, IL-15ΔE6, generated by alternative splicing events of activated immune cells, including macrophages and B cells. In vitro study showed that IL-15ΔE6 could antagonize IL-15-mediated T cell proliferation. The receptor binding assay revealed that IL-15ΔE6 could bind to IL-15Rα and interfere with the binding between IL-15 and IL-15Rα. Over-expression of IL-15ΔE6 in the murine EAE model ameliorated the EAE symptoms of the mice. The clinical scores were significantly lower in the mice expressing IL-15ΔE6 than the control mice and the mice expressing IL-15. The inflammation and demyelination of the EAE mice expressing IL-15ΔE6 were less severe than the control group. Furthermore, flow cytometry analysis demonstrated that IL-15ΔE6 expression reduced the percentages of inflammatory T cells in the spleen and spinal cord, and inhibited the infiltration of macrophages to the CNS. Our results demonstrated that IL-15ΔE6 could be induced during immune activation and function as a negative feedback mechanism to dampen IL-15-mediated inflammatory events.

No MeSH data available.


Related in: MedlinePlus