• The Microorganisms and Industry
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• v.16 no.3
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• pp.2-5
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• 1990

IgA is the predominant immunoglobulin isotype in mucosal secretions(1). It has been reported that a population of Peyer's patch T cells can selectively induce IgM bearing B cells to switch to surface IgA bearing B cells(2,3). Further, IL-4, IL-5, and IL-6 alone and in combination, can significantly influence murine IgA B cell differentiation in vitro(4-7). However, it remains an open question which cytokines have a major role in class switching to the IgA isotype. Recently, it has been reported that transforming growth factor .betha.1(TGF .betha.1) alone, or in combination with IL-2 increases IgA secretion by LPS-activated surface IgA negative (sIgA$\^$-/) murine spleen B cells while concurrently downregulating IgM and IgG secretion by such cells(8-11). In the present study, limiting dilution analysis was used to demonstrate, at the clonal level, that TGF .betha.1 has siginificant activity as an IgA isotype switch factor.

• IMMUNE NETWORK
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• v.4 no.4
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• pp.216-223
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• 2004

Background: It is well known that IgA isotype switching is induced by $TGF-{\beta}1$. LPS-activated mouse normal B cells well differentiate into IgA secreting plasma cells under the influence of $TGF-{\beta}1$. Nevertheless, there are lots of difficulties in studying normal B cells in detail because it is not simple to obtain highly purified B cells, showing low reproducibility and transfection efficacy, moreover impossible to keep continuous culture. To overcome these obstacles, it is desperately needed to develop B cell line which acts like normal B cells. In the present study, we investigated whether CH12F3-2A lymphoma cells are appropriate for studying IgA isotype switching event. Methods: CH12F3-2A B cell line was treated with LPS and $TGF-{\beta}1$, then levels of germ-line (GL) transcripts were measured by RT-PCR, and $GL{\alpha}$ promoter activity was measured by luciferase assay. In addition, membrane IgA (mIgA) expression and IgA secretion were determined by FACS and ELISA, respectively. Results: $TGF-{\beta}1$, regardless of the presence of LPS, increased level of $GL{\alpha}$ transcripts but not $GL{\gamma}2b$ transcripts. However, IgA secretion was increased dramatically by co-stimulation of LPS and $TGF-{\beta}1$. Both mIgA and IgA secretion in the presence of $TGF-{\beta}1$ were further increased by over-expression of Smad3/4. Finally, $GL{\alpha}$ promoter activity was increased by $TGF-{\beta}1$. Conclusion: CH12F3-2A cell line acts quite similarly to the normal B cells which have been previously reported regarding IgA expression. Thus, CH12F3-2A lymphoma cell line appears to be adequate for the investigation of the mechanism(s) of IgA isotype switching at the cellular and molecular levels.

• IMMUNE NETWORK
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• v.15 no.1
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• pp.37-43
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• 2015

It is well established that TGF-${\beta}1$ and retinoic acid (RA) cause IgA isotype switching in mice. We recently found that lactoferrin (LF) also has an activity of IgA isotype switching in spleen B cells. The present study explored the effect of LF on the Ig production by mouse peritoneal B cells. LF, like TGF-${\beta}1$, substantially increased IgA production in peritoneal B1 cells but little in peritoneal B2 cells. In contrast, LF increased IgG2b production in peritoneal B2 cells much more strongly than in peritoneal B1 cells. LF in combination with RA 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 to expression of gut homing molecules ${\alpha}4{\beta}7$ and CCR9 on peritoneal B1 cells, but not on peritoneal B2 cells. Thus, these results indicate that LF and RA can contribute to gut IgA response through stimulating IgA isotype switching and expression of gut-homing molecules in peritoneal B1 cells.

• Journal of Microbiology
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• v.37 no.3
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• pp.180-184
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• 1999

hybridoma cells producing IgM anti-pneuococcal 6B polysaccharide antibodies were induced to switch to IgG-producing cells in vitro by treating with acridine orange. Treating 0.5 $\mu\textrm{g}$/ml of acridine orange for 24 hours generated maximal number of variant cells. The maximal isotype switch frequency was 3${\times}$10-5, which is about 30-fold higher than the frequency of spontaneous switching. Resulting IgG-producing variants were enriched by sib selection and ELISA spot assay. Two IgG3-producing variant cells were finally cloned by limiting dilution. The variant cells produced similar amounts of antibodies as their parental cells did. The two switched antibodies had similar reactivity to pneumococcal 6B polysaccharide. When compared to their parental IgM antibodies, the switched IgG3 than that of IgM antibody. The antibodies will be useful as essential tools for comparative study of the role of heavy chain isotypes in protection against Streptococcus pneumoniae.

• BMB Reports
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• v.29 no.2
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• pp.127-132
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• 1996

Germinal centers (GCs) are formed in peripheral lymphoid tissues in response to protein antigens. In order to see if immunoglobulin isotype switching takes place in GC B-cells, we isolated GC B-cells (PNA positive cells) from mouse popliteal lymph nodes by a flow cytometer after the staining of lymph node cells with PNA-FITC and anti-B220-PE, and determined the expression of ${\gamma}1$ germline transcript and ${\gamma}1$ mRNA by RT-PCR. ${\gamma}1$ germline transcript and ${\gamma}1$ mRNA were amplified specifically in cDNAs from hybridoma expressing IgG1 or splenocytes stimulated LPS plus IL-4. Germinal center B-cells formed in popliteal lymph nodes of mice immunized with chicken ovalbumin were isolated 7 days after immunization. We sorted GC B-cells five times. Immunoglobulin ${\gamma}1$ germline transcripts were expressed in germinal center B-cells in three out of five sorts whereas two out of five sorts did not express ${\gamma}1$ germline transcripts in GC B-cells. The contents of GC B-cells ranged from 5 to 7% of total lymph node cells in most flow cytometric analyses but those of two sorted cells which did not express ${\gamma}1$ germline transcripts were out of normal range. These results imply that isotype switching of immunoglobulins may take place in GCs.

• Molecules and Cells
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• v.19 no.3
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• pp.445-451
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• 2005

Activation-induced cytidine deaminase (AID) is needed for Ig class switch recombination (CSR). We explored the effect of LPS on the expression of AID during B cell differentiation, and the role of AID in IgA isotype expression. In normal spleen B cells, LPS increased AID transcription up to 48 h post-stimulation, i.e. around the time of Ig CSR. TGF-${\beta}1$ and AID were required for IgA expression, and LPS contributed to $TGF{\beta}1$-induced IgA production largely by inducing AID. Interestingly, LPS repressed AID transcription in $sIgA^+$ B cells but still stimulated IgA production mainly by increasing the rate of IgA secretion. Our data indicate that LPS contributes to $TGF{\beta}1$-induced IgA isotype expression in at least two ways: by stimulating AID transcription before CSR and by enhancing the IgA secretion rate after CSR.

• IMMUNE NETWORK
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• v.13 no.1
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• pp.10-15
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• 2013

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 $GLT{\gamma}1$ expression. These results demonstrate that alum can directly cause IgG1 isotype switching leading to IgG1 production.

• IMMUNE NETWORK
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• v.12 no.1
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• pp.27-32
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• 2012

Background: Toll-like receptors (TLRs) have been extensively studied in recent years. However, functions of these molecules in murine B cell biology are largely unknown. A TLR4 stimulant, LPS is well known as a powerful polyclonal activator for murine B cells. Methods: In this study, we explored the effect of a murine TLR9 stimulant, M6-395 (a synthetic CpG ODNs) on B cell proliferation and Ig production. Results: First, M6-395 was much more potent than LPS in augmenting B cell proliferation. As for Ig expression, M6-395 facilitated the expression of both TGF-${\beta}1$-induced germ line transcript ${\alpha}$ ($GLT{\alpha}$) and IL-4-induced $GLT{\gamma}1$ as levels as those by LPS and Pam3CSK4 (TLR1/2 agonist) : a certain Ig GLT expression is regarded as an indicative of the corresponding isotype switching recombination. However, IgA and IgG1 secretion patterns were quite different--these Ig isotype secretions by M6-395 were much less than those by LPS and Pam3CSK4. Moreover, the increase of IgA and IgG1 production by LPS and Pam3CSK4 was virtually abrogated by M6-395. The same was true for the secretion of IgG3. We found that this unexpected phenomena provoked by M6-395 is attributed, at least in part, to its excessive mitogenic nature. Conclusion: Taken together, these results suggest that M6-395 can act as a murine polyclonal activator but its strong mitogenic activity is unfavorable to Ig isotype switching.

• IMMUNE NETWORK
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• v.5 no.4
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• pp.215-220
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• 2005

Background: Transforming growth factor-${\beta}$ (TGF-${\beta}1$) 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 (GLT ${\alpha}$), post-switch transcripts (PST ${\alpha}$) and circle transcripts (CT ${\alpha}$) 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: GLT ${\alpha}$ and PST ${\alpha}$ were well expressed in PP and MLN cells but in spleen cells. Similar patterns were observed in the expression of GL ${\gamma}$2b and PST ${\gamma}$2b. On the other hand, these transcripts were only inducible in spleen cells upon stimulated with LPS and TGF-${\beta}1$. In addition, CT${\alpha}$ and CT${\gamma}$2b 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.

• IMMUNE NETWORK
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• v.9 no.6
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• pp.248-254
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• 2009

[ $TGF-{\beta}1$ ]is well known to induce Ig germ-line ${\alpha}$ ($GL{\alpha}$) 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 $TGF-{\beta}$ signaling. In the present study, we investigated the roles of Tiul1 and TGIF in $TGF{\beta}1$-induced IgA CSR. We found that over-expression of Tiul1 decreased $TGF{\beta}1$-induced $GL{\alpha}$ promoter activity and strengthened the inhibitory effect of Smad7 on the promoter activity. Likewise, overexpression of TGIF also diminished $GL{\alpha}$ promoter activity and further strengthened the inhibitory effect of Tiul1, suggesting that Tiul1 and TGIF can down-regulate $TGF{\beta}1$-induced $GL{\alpha}$ expression. In parallel, overexpression of Tiul1 decreased the expression of endogenous IgA CSR-predicitive transcripts ($GLT_{\alpha},\;PST_{\alpha},\;and\;CT_{\alpha}$) and $TGF{\beta}1$-induced IgA secretion, but not $GLT_{\gamma3}$ 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 $TGF{\beta}1$-induced IgA isotype expression.