IL-2 activation of STAT5 enhances production of IL-10 from human cytotoxic regulatory T cells, HOZOT.
OBJECTIVE
Interleukin (IL)-10 is an immunosuppressive cytokine produced by many cell types, including T cells. We previously reported that a novel type of regulatory T (Treg) cells, termed HOZOT, which possesses a FOXP3+CD4+CD8+CD25+ phenotype and dual suppressor/cytotoxic activities, produced high levels of IL-10. In this study, we examined the mechanisms of high IL-10 production by HOZOT, focusing on Janus activating kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway.


METHODS
We prepared five different types of T cells, including HOZOT from human umbilical cord blood. Cytokine productions of IL-10, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) were compared among these T cells after anti-CD3/CD28 antibody stimulation in the presence or absence of IL-2. Specific inhibitors for JAK/STAT, nuclear factor-kappaB (NF-kappaB), and nuclear factor for activated T cell (NFAT) were used to analyze signal transduction mechanisms.


RESULTS
IL-10 production by HOZOTs was greatly enhanced by the addition of IL-2. Little or no enhancement of IFN-gamma and TNF-alpha production was observed under the same conditions. The enhancing effect of IL-2 was specific for both HOZOT and IL-10-secreting Treg cells. T helper type 2 cells, whose IL-10 production mechanisms involve GATA-3, failed to show IL-2-mediated enhancement of IL-10. Similar enhancing effects of IL-15 and IFN-alpha suggested a major role of JAK/STAT activation pathway for high IL-10 production. Further inhibitor experiments demonstrated that STAT5 rather than STAT3 was critically involved in this mechanism.


CONCLUSIONS
Our results demonstrated that IL-2 selectively enhanced production of IL-10 in HOZOT primarily through activation of STAT5, which synergistically acts with NF-kappaB/NFAT activation, implying a novel regulatory mechanism of IL-10 production in Treg cells.
Tsuji-Takayama
Kazue
K
Cell Biology Institute, Research Center, Hayashibara Biochemical Laboratories, Inc., Fujisaki, Okayama, Japan. kztakayama@hayashibara.co.jp
Suzuki
Motoyuki
M
Yamamoto
Mayuko
M
Harashima
Akira
A
Okochi
Ayumi
A
Otani
Takeshi
T
Inoue
Toshiya
T
Sugimoto
Akira
A
Motoda
Ryuichi
R
Yamasaki
Fumiyuki
F
Nakamura
Shuji
S
Kibata
Masayoshi
M
D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D016898:Interferon-alpha / Q000096:biosynthesis / Q000276:immunology; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D016753:Interleukin-10 / Q000096:biosynthesis / Q000276:immunology*; D019409:Interleukin-15 / Q000096:biosynthesis / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology* / Q000494:pharmacology; D053612:Janus Kinases / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D050778:NFATC Transcription Factors / Q000276:immunology / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000276:immunology / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000276:immunology
D000906:Antibodies; D015703:Antigens, CD; C508609:IL10 protein, human; C508594:IL2 protein, human; D016898:Interferon-alpha; D019409:Interleukin-15; D007376:Interleukin-2; D050778:NFATC Transcription Factors; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D007371:Interferon-gamma; D053612:Janus Kinases