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Differential roles of interleukin 15 mRNA isoforms generated by alternative splicing in immune responses in vivo.

Nishimura H, Yajima T, Naiki Y, Tsunobuchi H, Umemura M, Itano K, Matsuguchi T, Suzuki M, Ohashi PS, Yoshikai Y - J. Exp. Med. (2000)

Bottom Line: At least two types of interleukin (IL)-15 mRNA isoforms are generated by alternative splicing at the 5' upstream of exon 5 in mice.On the other hand, a large amount of intracellular IL-15 protein was detected but hardly secreted extracellularly in alternative IL-15 Tg mice.Thus, two groups of IL-15 Tg mice may provide information concerning the different roles of IL-15 isoforms in the immune system in vivo.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Host Defense & Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya 466, Japan. nishihit@med.nagoya-u.ac.jp

ABSTRACT
At least two types of interleukin (IL)-15 mRNA isoforms are generated by alternative splicing at the 5' upstream of exon 5 in mice. To elucidate the potential roles of IL-15 isoforms in immune responses in vivo, we constructed two groups of transgenic mice using originally described IL-15 cDNA with a normal exon 5 (normal IL-15 transgenic [Tg] mice) and IL-15 cDNA with an alternative exon 5 (alternative IL-15 Tg mice) under the control of an MHC class I promoter. Normal IL-15 Tg mice constitutionally produced a significant level of IL-15 protein and had markedly increased numbers of memory type (CD44(high) Ly6C(+)) of CD8(+) T cells in the LN. These mice showed resistance to Salmonella infection accompanied by the enhanced interferon (IFN)-gamma production, but depletion of CD8(+) T cells exaggerated the bacterial growth, suggesting that the IL-15-dependent CD8(+) T cells with a memory phenotype may serve to protect against Salmonella infection in normal IL-15 Tg mice. On the other hand, a large amount of intracellular IL-15 protein was detected but hardly secreted extracellularly in alternative IL-15 Tg mice. Although most of the T cells developed normally in the alternative IL-15 Tg mice, they showed impaired IFN-gamma production upon TCR engagement. The alternative IL-15 transgenic mice were susceptible to Salmonella accompanied by impaired production of endogenous IL-15 and IFN-gamma. Thus, two groups of IL-15 Tg mice may provide information concerning the different roles of IL-15 isoforms in the immune system in vivo.

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Generation of CD4 Th1 cells specific for Salmonella antigen in IL-15 Tg mice. CD4+ T cells (2 × 105 cells) or CD8+ T cells (2 × 105 cells) in LN of IL-15 Tg mice or control mice on day 6 after an i.p. challenge with S. choleraesuis (2 × 106 CFU) were purified by MACS and cultured with or without heat-killed Salmonella in the presence of MMC-treated splenocytes (106 cells) for 3 d at 37°C. Thereafter, the supernatants were collected and cytokine activity was determined by ELISA. The data are representative of three independent experiments using pooled cells from five IL-15 Tg or control mice and shown as the mean of triplicate determinations ± SD. Statistical analysis was performed by means of Student's t test. Significant differences compared with the values in control mice are shown: *P < 0.01.
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Figure 10: Generation of CD4 Th1 cells specific for Salmonella antigen in IL-15 Tg mice. CD4+ T cells (2 × 105 cells) or CD8+ T cells (2 × 105 cells) in LN of IL-15 Tg mice or control mice on day 6 after an i.p. challenge with S. choleraesuis (2 × 106 CFU) were purified by MACS and cultured with or without heat-killed Salmonella in the presence of MMC-treated splenocytes (106 cells) for 3 d at 37°C. Thereafter, the supernatants were collected and cytokine activity was determined by ELISA. The data are representative of three independent experiments using pooled cells from five IL-15 Tg or control mice and shown as the mean of triplicate determinations ± SD. Statistical analysis was performed by means of Student's t test. Significant differences compared with the values in control mice are shown: *P < 0.01.

Mentions: Early IFN-γ production plays an important role not only in host defense at the early stage, but also in determining differentiation of naive CD4+ T cells to Th1 cells during infection with Salmonella species. Therefore, we next compared the generation of CD4+ Th1 cells specific for Salmonella in normal and alternative IL-15 Tg mice. As shown in Fig. 10, CD4+ T cells from normal IL-15 Tg mice on day 6 after the i.p. challenge with S. choleraesuis produced a larger amount of IFN-γ in response to HKS than did those from control mice, while CD4+ T cells in the LN of alternative IL-15 Tg mice produced a smaller amount of IFN-γ than did those in control mice. CD8+ T cells from normal IL-15 Tg mice or control mice produced only a small amount of IFN-γ in response to HKS. On the other hand, no IFN-γ production was evident in the CD8+ T cells from alternative IL-15 Tg mice on day 6 after infection with S. choleraesuis. These results suggest that Th1 cells are efficiently generated in normal IL-15 Tg mice but poorly generated in alternative IL-15 Tg mice.


Differential roles of interleukin 15 mRNA isoforms generated by alternative splicing in immune responses in vivo.

Nishimura H, Yajima T, Naiki Y, Tsunobuchi H, Umemura M, Itano K, Matsuguchi T, Suzuki M, Ohashi PS, Yoshikai Y - J. Exp. Med. (2000)

Generation of CD4 Th1 cells specific for Salmonella antigen in IL-15 Tg mice. CD4+ T cells (2 × 105 cells) or CD8+ T cells (2 × 105 cells) in LN of IL-15 Tg mice or control mice on day 6 after an i.p. challenge with S. choleraesuis (2 × 106 CFU) were purified by MACS and cultured with or without heat-killed Salmonella in the presence of MMC-treated splenocytes (106 cells) for 3 d at 37°C. Thereafter, the supernatants were collected and cytokine activity was determined by ELISA. The data are representative of three independent experiments using pooled cells from five IL-15 Tg or control mice and shown as the mean of triplicate determinations ± SD. Statistical analysis was performed by means of Student's t test. Significant differences compared with the values in control mice are shown: *P < 0.01.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2195806&req=5

Figure 10: Generation of CD4 Th1 cells specific for Salmonella antigen in IL-15 Tg mice. CD4+ T cells (2 × 105 cells) or CD8+ T cells (2 × 105 cells) in LN of IL-15 Tg mice or control mice on day 6 after an i.p. challenge with S. choleraesuis (2 × 106 CFU) were purified by MACS and cultured with or without heat-killed Salmonella in the presence of MMC-treated splenocytes (106 cells) for 3 d at 37°C. Thereafter, the supernatants were collected and cytokine activity was determined by ELISA. The data are representative of three independent experiments using pooled cells from five IL-15 Tg or control mice and shown as the mean of triplicate determinations ± SD. Statistical analysis was performed by means of Student's t test. Significant differences compared with the values in control mice are shown: *P < 0.01.
Mentions: Early IFN-γ production plays an important role not only in host defense at the early stage, but also in determining differentiation of naive CD4+ T cells to Th1 cells during infection with Salmonella species. Therefore, we next compared the generation of CD4+ Th1 cells specific for Salmonella in normal and alternative IL-15 Tg mice. As shown in Fig. 10, CD4+ T cells from normal IL-15 Tg mice on day 6 after the i.p. challenge with S. choleraesuis produced a larger amount of IFN-γ in response to HKS than did those from control mice, while CD4+ T cells in the LN of alternative IL-15 Tg mice produced a smaller amount of IFN-γ than did those in control mice. CD8+ T cells from normal IL-15 Tg mice or control mice produced only a small amount of IFN-γ in response to HKS. On the other hand, no IFN-γ production was evident in the CD8+ T cells from alternative IL-15 Tg mice on day 6 after infection with S. choleraesuis. These results suggest that Th1 cells are efficiently generated in normal IL-15 Tg mice but poorly generated in alternative IL-15 Tg mice.

Bottom Line: At least two types of interleukin (IL)-15 mRNA isoforms are generated by alternative splicing at the 5' upstream of exon 5 in mice.On the other hand, a large amount of intracellular IL-15 protein was detected but hardly secreted extracellularly in alternative IL-15 Tg mice.Thus, two groups of IL-15 Tg mice may provide information concerning the different roles of IL-15 isoforms in the immune system in vivo.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Host Defense & Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya 466, Japan. nishihit@med.nagoya-u.ac.jp

ABSTRACT
At least two types of interleukin (IL)-15 mRNA isoforms are generated by alternative splicing at the 5' upstream of exon 5 in mice. To elucidate the potential roles of IL-15 isoforms in immune responses in vivo, we constructed two groups of transgenic mice using originally described IL-15 cDNA with a normal exon 5 (normal IL-15 transgenic [Tg] mice) and IL-15 cDNA with an alternative exon 5 (alternative IL-15 Tg mice) under the control of an MHC class I promoter. Normal IL-15 Tg mice constitutionally produced a significant level of IL-15 protein and had markedly increased numbers of memory type (CD44(high) Ly6C(+)) of CD8(+) T cells in the LN. These mice showed resistance to Salmonella infection accompanied by the enhanced interferon (IFN)-gamma production, but depletion of CD8(+) T cells exaggerated the bacterial growth, suggesting that the IL-15-dependent CD8(+) T cells with a memory phenotype may serve to protect against Salmonella infection in normal IL-15 Tg mice. On the other hand, a large amount of intracellular IL-15 protein was detected but hardly secreted extracellularly in alternative IL-15 Tg mice. Although most of the T cells developed normally in the alternative IL-15 Tg mice, they showed impaired IFN-gamma production upon TCR engagement. The alternative IL-15 transgenic mice were susceptible to Salmonella accompanied by impaired production of endogenous IL-15 and IFN-gamma. Thus, two groups of IL-15 Tg mice may provide information concerning the different roles of IL-15 isoforms in the immune system in vivo.

Show MeSH
Related in: MedlinePlus