Alum Directly Modulates Murine B Lymphocytes to Produce IgG1 Isotype

진보라,서구영,김평현,김선진,이정민,강성호,한혜주,장영생 대한면역학회 2013 Immune Network Vol.13 No.1

Aluminum hydroxide (alum) is the most widely used adjuvant in human vaccines. Nevertheless, it is virtually unknown whether alum acts on B cells. In the present study, we explored the direct effect of alum on Ig expression by murine B cells in vitro. LPS-activated mouse spleen B cells were cultured with alum, and the level of isotype-specific Ig secretion,IgG1 secreting cell numbers, and Ig germ-line transcripts (GLT) were measured using ELISA, ELISPOT, and RT-PCR,respectively. Alum consistently enhanced total IgG1 production,numbers of IgG1 secreting cells, and GLTγ1expression. These results demonstrate that alum can directly cause IgG1 isotype switching leading to IgG1 production.

Molecular Analysis of TGF-β1-induced BAFF Promoter Activity in Mouse Antigen Presenting Cells

김현아,서구영,이화정,박재봉,김평현 한국유전학회 2007 Genes & Genomics Vol.29 No.4

BAF, one of the TNF ligand family, is primarily expresed by APCs such as macrophages eration, differentiation, survival, a n d I g p r o d u c t i o n o f B c e l s . I n t h e p r e s e n t s t u d y , w e a i m e d t o elucidate the molecular mechanisms by which TGF-1 induce BAFF expresion in order to gain a clue if TGF-1 may regulate B cell differentiation through influencing APCs. We found that TGF-1 pical TGF- signaling pathway is involved. Thus, Smad3 and Smad4 promoted BAF promoter activity in mouse dendritic cels and macrophages. Further, from the analysis of the BAF mutated promoters, we identified three putative Smad binding elements (SBEs) where Smad3 actually binds. These elements were indispensable for the promoter activity.

TGF-β and BAFF derived from CD4+CD25+Foxp3+ T cells mediate mouse IgA isotype switching

박경훈,서구영,장영생,김평현 한국유전학회 2012 Genes & Genomics Vol.34 No.6

TGF-β1 is generally accepted as the physiological IgA isotype switch factor. Nevertheless, it is unclear as to which cells in mucus-associated lymphoid tissue provide this cytokine to B cells. Regulatory T cells (Tregs) play immune-suppressive roles by secreting inhibitory cytokines such as TGF-β and IL-10. Thus, it is plausible that Tregs are involved in IgA class switch recombination (CSR) in MALT. We explored, in the present study, the possibility that CD4+CD25+ T cells facilitate IgA CSR in murine B cells. In cocultures,CD4+CD25+Foxp3+ T cells stimulated IgA production by splenic B cells to a greater extent than did CD4+CD25-Foxp3-T cells. This effect was markedly abrogated by the addition of anti-TGF-β1 Ab. Additionally, IgA production was paralleled by an increase in germ line transcript α (GLTα), an indicator of IgA CSR. In contrast, CD4+CD25-Foxp3- T cells were more potent at inducing GLTγ1 and GLTε production by cocultured splenic B cells than were CD4+CD25+Foxp3+T cells. Consistent with these results, phenotypic analyses revealed that TGF-β1 and IL-4 were predominantly expressed by CD4+CD25+Foxp3+ T cells and CD4+CD25-Foxp3- T cells,respectively. Furthermore, CD4+CD25+ T cells strongly expressed BAFF, which led to activation-induced deaminase (AID) expression in B cells. Taken together, our results suggest that CD4+CD25+ Tregs have an important effect on IgA isotype commitment by expressing TGF-β1 and BAFF in MALT.

Tiul1 and TGIF are Involved in Downregulation of TGFβ1-induced IgA Isotype Expression

박경훈,남은희,서구영,서수련,김평현 대한면역학회 2009 Immune Network Vol.9 No.6

TGF-β1 is well known to induce Ig germ-line α (GLα) transcription and subsequent IgA isotype class switching recombination (CSR). Homeodomain protein TG-interacting factor (TGIF) and E3-ubiquitin ligases TGIF interacting ubiquitin ligase 1 (Tiul1) are implicated in the negative regulation of TGF-β signaling. In the present study, we investigated the roles of Tiul1 and TGIF in TGFβ1-induced IgA CSR. We found that over-expression of Tiul1 decreased TGFβ1-induced GLα promoter activity and strengthened the inhibitory effect of Smad7 on the promoter activity. Likewise, overexpression of TGIF also diminished GLα promoter activity and further strengthened the inhibitory effect of Tiul1, suggesting that Tiul1 and TGIF can down-regulate TGFβ1- induced GLα expression. In parallel, overexpression of Tiul1 decreased the expression of endogenous IgA CSR-predicitive transcripts (GLTα, PSTα, and CTα) and TGFβ1-induced IgA secretion, but not GLTγ3 and IgG3 secretion. Here, over-expressed TGIF further strengthened the inhibitory effect of Tiul1. These results suggest that Tiul1 and TGIF act as negatively regulators in TGFβ1-induced IgA isotype expression. TGF-β1 is well known to induce Ig germ-line α (GLα) transcription and subsequent IgA isotype class switching recombination (CSR). Homeodomain protein TG-interacting factor (TGIF) and E3-ubiquitin ligases TGIF interacting ubiquitin ligase 1 (Tiul1) are implicated in the negative regulation of TGF-β signaling. In the present study, we investigated the roles of Tiul1 and TGIF in TGFβ1-induced IgA CSR. We found that over-expression of Tiul1 decreased TGFβ1-induced GLα promoter activity and strengthened the inhibitory effect of Smad7 on the promoter activity. Likewise, overexpression of TGIF also diminished GLα promoter activity and further strengthened the inhibitory effect of Tiul1, suggesting that Tiul1 and TGIF can down-regulate TGFβ1- induced GLα expression. In parallel, overexpression of Tiul1 decreased the expression of endogenous IgA CSR-predicitive transcripts (GLTα, PSTα, and CTα) and TGFβ1-induced IgA secretion, but not GLTγ3 and IgG3 secretion. Here, over-expressed TGIF further strengthened the inhibitory effect of Tiul1. These results suggest that Tiul1 and TGIF act as negatively regulators in TGFβ1-induced IgA isotype expression.

Murine γδ T Cells Render B Cells Refractory to Commitment of IgA Isotype Switching

한혜주,장영생,서구영,박성규,강승구,윤성일,고현정,이근식,김평현 대한면역학회 2018 Immune Network Vol.18 No.4

γδ T cells are abundant in the gut mucosa and play an important role in adaptive immunity as well as innate immunity. Although γδ T cells are supposed to be associated with the enhancement of Ab production, the status of γδ T cells, particularly in the synthesis of IgA isotype, remains unclear. We compared Ig expression in T cell receptor delta chain deficient (TCRδ−/−) mice with wild-type mice. The amount of IgA in fecal pellets was substantially elevated in TCRδ−/− mice. This was paralleled by an increase in surface IgA expression and total IgA production by Peyer's patches (PPs) and mesenteric lymph node (MLN) cells. Likewise, the TCRδ−/− mice produced much higher levels of serum IgA isotype. Here, surface IgA expression and number of IgA secreting cells were also elevated in the culture of spleen and bone marrow (BM) B cells. Germ-line α transcript, an indicator of IgA class switch recombination, higher in PP and MLN B cells from TCRδ−/− mice, while it was not seen in inactivated B cells. Nevertheless, the frequency of IgA+ B cells was much higher in the spleen from TCRδ−/− mice. These results suggest that γδ T cells control the early phase of B cells, in order to prevent unnecessary IgA isotype switching. Furthermore, this regulatory role of γδ T cells had lasting effects on the long-lived IgA-producing plasma cells in the BM.

Activin A Stimulates Mouse APCs to Express BAFF via ALK4-Smad3 Pathway

김재희,김평현,서구영 대한면역학회 2011 Immune Network Vol.11 No.4

Background: B cell-activating factor belonging to the TNF family (BAFF) is primarily expressed by macrophages and dendritic cells, and stimulates B cell proliferation, differentiation, survival, and Ig production. In the present study, we explored the effect of activin A on BAFF expression by APCs. Methods: To investigate the effect of activin A on BAFF expression by mouse APCs, we measured the level of BAFF expression at the transcriptional and protein levels using RT-PCR and ELISA. Results: Activin A markedly enhanced BAFF expression in mouse macrophages and dendritic cells at both the transcriptional and protein levels. SB431542, an activin receptor-like kinase 4 (ALK4) inhibitor, completely abrogated activin A-induced BAFF transcription. Furthermore, overexpression of DN-Smad3 abolished activin-induced BAFF expression at the transcriptional and protein levels. Conclusion: These results demonstrate that activin A can enhance BAFF expression through ALK4-Smad3 pathway.

마우스 내장 림프조직에서 우세하게 발현되는 IgA isotype switching 관련 전사체의 분석

채병철,전성기,김현아,서구영,김평현 대한면역학회 2005 Immune Network Vol.5 No.4

Background: Transforming growth factor-β1 (TGF-β1) directs class switch recombination (CSR) to IgA isotype, which is a predominant antibody in mucosal surfaces. Although IgA is preferentially committed in mucosal lymphoid tissues, it is not definitely established whether hallmarks of IgA CSR such as IgA germ-line transcripts (GLTα), post-switch transcripts (PSTα) and circle transcripts (CTα) are readily expressed in such tissues. Therefore, we compared the expression of these transcripts among mouse Peyer's patches (PP), mesenteric lymph nodes (MLN), and spleen. Methods: Levels of GLTs, PSTs and CTs were measured by RT-PCR in isolated PPs, MLNs and spleen cells. Results: GLTα and PSTα were well expressed in PP and MLN cells but in spleen cells. Similar patterns were observed in the expression of GLγ2b and PSTγ2b. On the other hand, these transcripts were only inducible in spleen cells upon stimulated with LPS and TGF-β1. In addition, CTα and CTγ2b were detected in PP cells. Conclusion: PP B cells readily express IgA GLT, PST, and CT. Overall expression patterns of these transcripts were similar in MLN cells. Thus, these results suggest that microenvironment of PP and MLN influences spontaneous IgA CSR, which lacks in systemic lymphoid tissues such as spleen.

Lactoferrin Combined with Retinoic Acid Stimulates B1 Cells to Express IgA Isotype and Gut-homing Molecules

강성호,진보라,김현진,서구영,장영생,김선진,안선진,박석래,김완섭,김평현 대한면역학회 2015 Immune Network Vol.15 No.1

It is well established that TGF-β1 and retinoic acid (RA)cause IgA isotype switching in mice. We recently found thatlactoferrin (LF) also has an activity of IgA isotype switchingin spleen B cells. The present study explored the effect of LFon the Ig production by mouse peritoneal B cells. LF, likeTGF-β1, substantially increased IgA production in peritonealB1 cells but little in peritoneal B2 cells. In contrast, LF increasedIgG2b production in peritoneal B2 cells much morestrongly than in peritoneal B1 cells. LF in combination withRA further enhanced the IgA production and, interestingly,this enhancement was restricted to IgA isotype and B1 cells. Similarly, the combination of the two molecules also led toexpression of gut homing molecules α4β7 and CCR9 onperitoneal B1 cells, but not on peritoneal B2 cells. Thus,these results indicate that LF and RA can contribute to gutIgA response through stimulating IgA isotype switching andexpression of gut-homing molecules in peritoneal B1 cells.

TGF-β1 Stimulates Mouse Macrophages to Express APRIL through Smad and p38MAPK/CREB Pathways

Young-Saeng Jang,김재희,서구영,김평현 한국분자세포생물학회 2011 Molecules and cells Vol.32 No.3

A proliferation-inducing ligand (APRIL), a new TNF family member, supports B-cell survival and tumor cell proliferation. APRIL is secreted as a soluble protein by macrophages,dendritic cells and activated T cells. However,factors involved in regulation of APRIL expression are as yet unknown. In this study, we investigated the effect of TGF-β1 on APRIL expression in P388D1, a mouse macrophage cell line. TGF-β1 induced APRIL mRNA expression in a time- and dose-dependent manner. One nanogram per milliliter of TGF-β1 was optimal and APRIL transcripts appeared as early as 3 h after stimulation. Based on our studies,which included overexpression of Smad3, DN-Smad3,and sh-Smad3, we found that Smad3 mediates APRIL transcription at least partially. Further, experiments using inhibitors revealed that p38MAPK and CREB are also involved in TGF-β1-induced APRIL expression. These results suggest that TGF-β1, through Smad3 and p38MAPK/CREB signaling pathways, stimulates APRIL expression in macrophages.

The PKA/CREB Pathway Is Closely Involved in VEGF Expression in Mouse Macrophages

Pyeung-Hyeun Kim,Seong-Hyun Jeon,Byung-Chul Chae,김현아,서구영,Dong-Wan Seo,Gie-Taek Chun,Se-Won Yie,Seok-Hyun Eom 한국분자세포생물학회 2007 Molecules and cells Vol.23 No.1