Bcl6 is required for the IL-4-mediated rescue of the B cells from apoptosis induced by IL-21

IL-21 has a pro-apoptotic effect on freshly isolated B cells stimulated with LPS, and also induces Bcl6 expression in the activated B cells. However, a role for Bcl6 in the activated B cells is not known. When naive B cells from Bcl6-deficient mice were stimulated with LPS plus IL-21, those B cells died by apoptosis as wild-type B cells. Co-stimulation of those B cells with IL-4 partially rescued the wild-type B cells but not the Bcl6-deficient B cells from the IL-21-induced apoptosis. Bcl-2 was not up-regulated in both B cells stimulated with LPS plus IL-21 and IL-4. Bcl-X(L) and Bax were up-regulated in both B cells stimulated with LPS plus IL-4, and the co-stimulation with IL-21 did not modulate these up-regulations in wild-type B cells. However, the co-stimulation clearly suppressed the Bcl-X(L) up-regulation but not the Bax up-regulation in Bcl6-deficient B cells. Thus, Bcl6 is required for maintaining the Bcl-X(L) up-regulation in B cells stimulated with LPS plus IL-21 and IL-4, and the up-regulation may partially rescue the B cells from apoptosis induced by IL-21.

Bcl6 is essential for the generation of long-term memory CD4+ T cells

Bcl6 plays a role in the generation and maintenance of memory CD8(+) T cells. We analyzed here a role for Bcl6 in the generation of long-term memory CD4(+) T cells. Naive CD45RB(+) CD4(+) T cells from Bcl6-deficient DO11.10 (KJ1.26(+)) transgenic mice were transferred into BALB/c mice and immunized with ovalbumin peptide and LPS. Long-term memory KJ1.26(+) CD4(+) T cells from wild-type mice were detected in the spleen, lungs and liver during 10 weeks after immunization; however, Bcl6-deficient KJ1.26(+) CD4(+) T cells were vanished completely in those organs 4 weeks after immunization. Since memory CD4(+) T cells can be generated from effector CD4(+) T cells, properties of Bcl6-deficient effector CD4(+) T cells were compared with those wild-type effector CD4(+) T cells 10 days after immunization. Numbers of IFN-gamma-non-producing CD45RB(-), CD62L(+) or IL-7Ralpha(+) effector CD4(+) T cells in the spleen, lungs and liver were similar between Bcl6-deficient and wild-type CD4(+) T cells. However, the percentage of apoptotic cells in Bcl6-deficient effector CD4(+) T cells was higher than that in wild-type effector CD4(+) T cells. At the late effector phase, the number of IFN-gamma-non-producing cells and the percentage of apoptotic cells in Bcl6-deficient CD4(+) T cells were smaller and higher than those in wild-type CD4(+) T cells, respectively. These data suggest that Bcl6 in CD4(+) T cells plays a role in protection of memory precursor CD4(+) T cells from apoptosis and may involve in survivability of long-term memory CD4(+) T cells.

Bcl6 controls granzyme B expression in effector CD8+ T cells

Bcl6, a sequence-specific transcriptional repressor, is important for generation and maintenance of memory CD8(+) T cells. Although memory CD8(+) T cells are generated from effector CD8(+) T cells, a role for Bcl6 in effector CD8(+) T cells is largely unknown. We show here that Bcl6 expression was transiently induced in activated CD8(+) T cells and continuously up-regulated in effector CD8(+) T cells. The amount of granzyme B mRNA among effector molecules produced by effector CD8(+) T cells inversely correlated with the amount of Bcl6 mRNA in CD8(+) T cells. Overexpression of Bcl6 in CD8(+) T cells resulted in lower killing activity at their effector phase, supporting the reduction of granzyme B expression in effector CD8(+) T cells by Bcl6. We identified a putative Bcl6-binding DNA sequence in the promoter region of the granzyme B gene. Binding of Bcl6 to the Bcl6-binding sequence was detected in naive CD8(+) T cells but not in activated CD8(+) T cells by chromatin immunoprecipitation assay. Furthermore, the Bcl6-binding sequence was required for Bcl6 to repress the luciferase reporter gene expression controlled by the granzyme B promoter. Thus, the granzyme B gene is a molecular target of Bcl6 in effector CD8(+) T cells.

Role of Clast1 in development of cerebellar granule cells

We have identified the murine Clast1/LR8 gene by subtraction of cDNA derived from CD40 ligand-activated and naive B cells. The Clast1 gene is ubiquitously expressed in various organs of adult mice. However, its physiological function was largely unknown. To study a role of Clast1, we established Clast1-deficient (Clast1-KO) mice. Here, we reveal that approximately 65% of Clast1-KO mice showed severe ataxia. The Clast1-KO cerebellum with ataxia is small in size and revealed a severely aberrant lobulation, loss of the internal granule cell layer, and the disorganized Purkinje cells. Clast1 mRNA is expressed in the cerebellar granule cells of normal adult mice. Developmentally, Clast1 mRNA is also detected in the external germinal layer of the embryonic cerebellum, indicating its expression in granule cell precursors. Histopathological analysis of the developing Clast1-KO cerebellum demonstrated the reduced number of cells in the external germinal layer. Thus, Clast1 is required for development of cerebellar granule cells.

JunD/AP-1 and STAT3 are the major enhancer molecules for high Bcl6 expression in germinal center B cells

The Bcl6 proto-oncogene, which encodes a transcriptional repressor, is ubiquitously expressed and predominantly in germinal center (GC) B cells. Although the promoter region of the human Bcl6 gene has been reported, enhancer molecules for its high expression in GC B cells were largely unknown. Here we show that transcriptional start sites of the murine Bcl6 gene were different from the reported human one. DNA sequence around the new promoter region is highly conserved between mice and humans and has no canonical TATA or CCAAT box. Two AP-1-binding elements in the promoter region were the major enhancer elements in GC-derived B lymphoma cells, and JunD/AP-1 was detected in GC B cells. In addition, we identified the silencer region with three Bcl6-binding elements around the start site. Bcl6 bound to the silencer elements and its over-expression repressed the promoter activity through the elements. Activated STAT factors (STATs), especially activated STAT3, also bound to the silencer elements in GC B cells and competed with Bcl6 for the binding, suggesting that JunD/AP-1 and activated STATs drive high Bcl6 expression in GC B cells. Since stimulation of splenic B cells with IL-4 or IL-21 induced high Bcl6 expression with induction of junD and activation of STATs, these cytokines may be inducers for its high expression in GC B cells. However, IL-21 but not IL-4 stimulation activated STAT3 in splenic B cells. Thus, IL-21 may be a major inducer for high Bcl6 expression in GC B cells.

A role for c-fos/activator protein 1 in B lymphocyte terminal differentiation

Expression of B lymphocyte-induced maturation protein 1 (Blimp-1) transcription factor is essential for promoting B cell differentiation into plasma cells. However, a critical transcription factor for Blimp-1 expression in activated B cells is unclear. When splenic B cells were stimulated with CD40 ligand (CD40L) and IL-4, terminal differentiation was induced in the B cells from c-fos transgenic (H2-c-fos) mice but barely in those from control littermates and from c-fos-deficient mice. AP-1 family and Blimp-1 mRNAs were transiently induced in the control B cells, and overexpression of c-Fos induced a sufficient amount of Blimp-1 for terminal differentiation in the H2-c-fos B cells. When normal and c-fos-deficient B cells were stimulated with LPS, a sufficient amount of Blimp-1 for terminal differentiation was induced in those B cells. However, expression of c-fos/AP-1 family mRNAs in LPS-stimulated normal B cells was similar to that of normal B cells stimulated with CD40L and IL-4. EMSA and chromatin immunoprecipitation assays using the AP-1-binding DNA sequence in the murine Blimp-1 promoter region demonstrated that AP-1-binding activity in nuclear protein of LPS-stimulated normal B cells was prolonged more than that in normal B cells stimulated with CD40L and IL-4. Furthermore, the percentage of CD138(+) B cells within germinal center B cells in the spleen and the number of Ab-forming cells in the bone marrow of H2-c-fos mice was larger than that of control mice 12 days after immunization. Thus, although c-Fos is not essential for Blimp-1 expression, c-Fos/AP-1 positively regulates Blimp-1 expression and terminal differentiation of activated B cells.

c- Overexpression in splenic B cells augments development of marginal zone B cells

Marginal zone (MZ)-B cells participate in very early immune responses and play a pivotal role in the first-line of defense against blood-borne Ags including bacterial LPS. Since splenic B cells from c-fos transgenic (H2-c-fos) mice are hyper-sensitive to LPS stimulation, we examined LPS-sensitivity of MZ-B cells in the spleen of H2-c-fos mice. Here, we show that proliferation of MZ-B cells from H2-c-fos mice stimulated with LPS was larger than that from control mice. Proliferation and IgM production of the H2-c-fos MZ-B cells were also larger than those of splenic follicular (FO)-B cells from the H2-c-fos mice, suggesting that c-fos overexpression augments LPS-sensitivity of MZ-B cells more than that of FO-B cells. Furthermore, the number of MZ-B cells but not that of FO-B cells in the spleen of H2-c-fos mice was two- to three-fold larger than that in control littermates. The number of transitional type II (T2)-B cells in H2-c-fos mice was also larger than that of control littermates. However, the number of transitional type I (T1)-B cells in the spleen of H2-c-fos mice was not larger than that of control mice. Moreover, this c-fos effect on differentiation of MZ-B cells was intrinsic in B cells by the competitive repopulation assay with hematopoietic stem cells of H2-c-fos and control mice. These results suggest that c-fos overexpression in B cells augments differentiation and accumulation of MZ-B cells.

Bcl6 regulates Th2 type cytokine productions by mast cells activated by FcepsilonRI/IgE cross-linking

Bcl6-deficient (Bcl6-/-) mice displayed Th2 type inflammation, which caused by abnormality of non-lymphoid cells. However, initiators for the Th2 type inflammation were not clear. In order to elucidate the initiators, we investigated property and function of mast cells derived from Bcl6-/- mice. Mast cells were developed from bone marrow cells cultured with IL-3 (BMMCs). Although the development of BMMCs from Bcl6-/- mice was similar to that from wild-type mice, proliferation of Bcl6-/- BMMCs stimulated with IL-3 was slightly lower than that of wild-type BMMCs. When these BMMCs were stimulated by FcepsilonRI/IgE cross-linking, Bcl6-/- BMMCs produced Th2 cytokines more than wild-type BMMCs did. Thus, Bcl6-/- mast cells are one of the initiators for Th2 type inflammation in Bcl6-/- mice, and Bcl6 may be a molecular target for Th2 type allergic diseases.

Abnormal erythroid differentiation in neonatal bcl-6-deficient mice

OBJECTIVE

The bcl-6 proto-oncogene is ubiquitously expressed in various tissues. Since we found out the smaller number of TER119(+) cells in the spleen of neonatal bcl-6-deficient (bcl-6(-/-)) mice compared with that of control (bcl-6(+/+)) littermates, we studied functions of bcl-6 in differentiation of erythroid lineage cells.

MATERIALS AND METHODS

Erythroblasts in the definitive erythropoiesis were separated into four subsets using anti-TER119 and anti-CD71 mAbs. The cell number and property of these four subsets in spleens of neonatal bcl-6(+/+) and bcl-6(-/-) mice were examined using a flow cytometry.

RESULTS

bcl-6 mRNA expression was detected in the TER119(high)CD71(high) subset, which is morphologically equivalent to basophilic erythroblasts, by reverse-transcribed polymerase chain reaction. High percentages of cells in the TER119(low)CD71(high) and TER119(high)CD71(high) subsets were in the cell cycle. The cell number of the TER119(high)CD71(high) subset in the spleen and the percentage of reticulocytes in the peripheral blood of neonatal bcl-6(-/-) mice were significantly lower than those of neonatal bcl-6(+/+) mice. However, the percentage of apoptotic cells and that of cells in the cell cycle in the TER119(high)CD71(high) subset of bcl-6(-/-) mice were similar to those of bcl-6(+/+) mice.

CONCLUSION

bcl-6 detected in the TER119(high)CD71(high) subset of erythroblasts in the spleen of neonatal mice may be required to retain the erythroblasts in the cell proliferation stage.

Beta-galactosidase of ROSA26 mice is a useful marker for detecting the definitive erythropoiesis after stem cell transplantation

BACKGROUND

Hematopoietic reconstitution after stem cell transplantation has been analyzed by using stem cells of Ly5 congenic mice. However, the early erythropoiesis has never been analyzed because this marker is not expressed on all of the erythroid lineage cells. The transgenic mouse expressing beta-galactosidase (beta-gal) or green fluorescent protein (GFP) has been reported. Using these markers, we analyzed the early erythropoiesis after stem cell transplantation.

METHODS

The beta-gal activity and GFP were examined in the hematopoietic cells of ROSA26 and GFP transgenic mice, respectively, by flow cytometry. The primitive hematopoietic stem cell fraction (Lin(-)c-kit(+)Sca-1(+)) in bone marrow (BM) cells of ROSA26 mice was transferred into lethally irradiated mice. The kinetics of hematopoietic reconstitution was analyzed in the BM and spleen after transplantation.

RESULTS

The beta-gal activity, but not the GFP and Ly5, was detected in all of the erythroid (TER119+) cells. The beta-gal activity was also detected in the donor-derived myeloid (Mac-1+), B lymphoid (B220+), and T lymphoid (Thy-1+) cells in the BM and spleen after stem cell transplantation. The kinetics of the hematopoietic reconstitution demonstrated that early erythroid (TER119(low)CD71(med)) cells were developed in the BM and spleen within 2 days after transplantation before development of proerythroblasts (TER119(+)CD71(high)), and that massive erythropoiesis and myelopoiesis were observed in the spleen until 2 and 4 weeks after transplantation, respectively. Conclusions. The beta-gal of ROSA26 mice can be a useful marker to identify the donor-derived hematopoietic cells, including early erythroid cells, and the first major wave of erythropoiesis occurring in the spleen after stem cell transplantation.

BAZF is required for activation of naive CD4 T cells by TCR triggering

BAZF, a member of the Bcl6 gene family, acts as a sequence-specific transcriptional repressor in association with Bcl6. However, the tissue expression pattern of BAZF differs from that of Bcl6, suggesting a Bcl6-independent function of BAZF. In order to examine the physiological function of BAZF, we generated BAZF-deficient mice and transgenic mice with BAZF-cDNA under the control of the lck proximal promoter (lck-BAZF). These mice were viable and no gross anatomical abnormalities were observed after birth. Since Bcl6 is a key molecule for the generation of memory T cells, we examined the function of T cells of these mice. We show here that cell proliferation of naive CD4 T cells, but not memory ones, of BAZF-deficient mice to anti-CD3 antibody stimulation was impaired. Conversely, cell proliferation of naive CD4 T cells, but not memory ones, of lck-BAZF mice was augmented. Since cell proliferation of naive CD4 T cells of lck-Bcl6 mice to anti-CD3 antibody stimulation was severely impaired, BAZF may attenuate the regulatory effect of Bcl6 on antigenic activation of naive CD4 T cells by Bcl6/BAZF heterodimer formation. These results suggest that BAZF is necessary for activation of naive T cells to antigenic stimulation.

Effect of c-fos overexpression on development and proliferation of peritoneal B cells

We examined effects of c-fos overexpression on the development and property of peritoneal B-1 cells using transgenic (H2-c-fos) mice carrying the c-fos gene under the control of the constitutive H-2Kb promoter. The number of B-1b cells in the peritoneal cavity of H2-c-fos mice was 4-fold larger than that in control littermates. Although the numbers of total peritoneal B cells and B-1a cells were similar between them, the peritoneal B-2 cell number in H2-c-fos mice was reduced to 50% of control littermates, suggesting the effect of c-fos overexpression on a balance of B-1b and B-2 cells in a peritoneal cavity. Adoptive transfer experiments with hematopoietic stem cells of H2-c-fos and control mice into irradiated H2-c-fos mice demonstrated that the augmentation of B-1b cells is due to the c-fos effect in B cells and the effect on environment of the peritoneal cavity of H2-c-fos mice. When peritoneal B cells were cultured with LPS in the presence or absence of IL-4, cell proliferation of B-1b cells was the highest among these peritoneal B cell subsets, and the proliferation of H2-c-fos B-1b cells was 3-fold higher than that of control B-1b cells. This augmentation is due to the c-fos effect in B cells. IgG1 production of B-1b cells in these cultures was slightly higher than those of B-1a and peritoneal B-2 cells. Thus, the c-fos overexpression augments development of B-1b cells in a peritoneal cavity and proliferation of peritoneal B-1b cells to LPS.

Effects of CD80 and CD86 on cytokine production in patients with wasp-venom allergy who receive venom immunotherapy

Several studies have provided evidence that activation of antigen-specific T cells requires interactions between CD28 on T cells and its ligands, CD80 and CD86, on antigen-presenting cells (APCs). However, the effects of CD80 and CD86 on cytokine production in patients with Hymenoptera venom allergy who receive venom immunotherapy remain unclear. We examined the effects of CD80 and CD86 on Th1- and Th2-cytokine production before and after venom immunotherapy in patients with wasp-venom allergy. Peripheral blood mononuclear cells (PBMCs) were isolated from patients with wasp-venom allergy before and after three months of venom immunotherapy. CD4+ T cells and monocytes were isolated as APCs from PBMCs and were cocultured with wasp venom in the presence of anti-CD80 or -CD86 blocking antibodies. Interleukin (IL)-4, IL-10, and interferon (IFN)-gamma were measured by enzyme-linked immunosorbent assay. The expression of CD80 and CD86 on CD14+ PBMCs was detected by fluorescence-activated cell-sorter analysis. The expression of CD86, but not that of CD80, on CD14+ PBMCs cocultured with venom increased after three months of venom immunotherapy, but not before venom immunotherapy. Blockade of CD86 reduced IL-10 production after three months of venom immunotherapy. IL-10 production promoted by CD86 costimulation may be involved in the mechanism of venom immunotherapy in patients with venom allergy.

Prostaglandin D2 reinforces Th2 type inflammatory responses of airways to low-dose antigen through bronchial expression of macrophage-derived chemokine

PGD2, a lipid mediator released from mast cells, is known to participate in allergic reactions. However, the mechanism by which PGD2 contributes to such reactions remains unclear. We established a novel experimental model of asthma that permitted direct assessment of the role of PGD2 in airway inflammation. Antigen-sensitized mice were exposed to aerosolized prostaglandin D2 (PGD2) 1 d before challenge with low-dose aerosolized antigen. Not only the numbers of eosinophils, lymphocytes, and macrophages but also the levels of IL-4 and IL-5 in bronchoalveolar lavage fluid were higher in PGD2-pretreated mice than in control mice. The expression of macrophage-derived chemokine (MDC), a chemoattractant for Th2 cells, was greater in PGD2-pretreated mice than in control. Injection of anti-MDC antibody into PGD2-pretreated mice markedly inhibited inflammatory cell infiltration as well as Th2 cyto-kine production after antigen challenge. These results indicate that PGD2 accelerates Th2 type inflammation by induction of MDC. Our results suggest that this mechanism may play a key role in the development of human asthma and that MDC might be a target molecule for therapeutic intervention.

Bcl6 is a transcriptional repressor for the IL-18 gene

Bcl6 functions as a sequence-specific transcriptional repressor, and Bcl6-deficient (Bcl6(-/-)) mice have been reported to display Th2-type inflammatory diseases in multiple organs. Since IL-18 is a potent stimulator of Th2 cells, we examined the expression of IL-18 mRNA in bone marrow-derived macrophages from Bcl6(-/-) mice after LPS stimulation. Here we show that the expression was strikingly up-regulated after stimulation. The expression was also up-regulated in RAW264 cells, a murine macrophage cell line, by transfection with the dominant negative type of Bcl6 gene. We identified a putative Bcl6-binding DNA sequence (IL-18BS) upstream of exon 1 of the murine IL-18 gene and three IL-18BSs in the promoter region of human IL-18 gene. Binding of Bcl6 in nuclear protein from resting RAW264 cells to murine IL-18BS was detected by gel retardation assay and chromatin immunoprecipitation assay. The binding activity was diminished gradually in RAW264 cells after LPS stimulation. However, the amount of Bcl6 protein in these cells was constant over the period examined, suggesting the functional modification of Bcl6 protein after stimulation. Furthermore, murine IL-18BS was required for Bcl6 to repress the expression of the luciferase reporter gene under control of the IL-18 promoter. Taken together, Bcl6 is a key regulator of IL-18 production by macrophages.

Efficacy and safety of rush immunotherapy in patients with Hymenoptera allergy in Japan

In Japan, approximately 40 persons die annually from anaphylaxis caused by Hymenoptera stings. Venom immunotherapy is considered safe and effective for the treatment of allergic systemic reactions caused by Hymenoptera stings in patients with Hymenoptera allergy. We studied the efficacy and safety of rush immunotherapy in patients who had a history of systemic reactions to Hymenoptera stings in Japan. Between 1988 and 2002, 95 patients with a history of systemic reactions to Hymenoptera stings were investigated. The stings originated from honeybees in 5 patients, yellow jackets in 28, wasps in 48, both yellow jackets and wasps in 9, and both yellow jackets and honeybees in 5. All patients had venom-specific IgE antibodies in sera (RAST score > or = 2) and received rush immunotherapy with venom extracts at our hospital. Forty-three patients had 63 field re-stings during immunotherapy. Of these patients, 41 (95.3%) with 59 field re-stings (93.7%) had no systemic reactions. Two patients (4.7%) with four field restings (6.3%) had anaphylactic shock. Although anaphylactic reactions developed in two patients (2.1%) during rush immunotherapy with honeybee venom and one patient (1.1%) during maintenance therapy wasp venom, systemic adverse reactions were mitigated by treatment with antihistamines before venom injection. Our results show that immunotherapy is safe and effective for the prevention of systemic reactions to Hymenoptera re-stings in patients with Hymenoptera allergy. We therefore recommend that patients who are allergic to Hymenoptera venom prophylactically receive immunotherapy.

Production of TARC and MDC by naive T cells in asthmatic patients

The helper (Th)2 cell-attracting chemokines thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC) are ligands for the chemokine receptor CCR4. A number of cellular sources of TARC and MDC have been identified, including not only macrophages, dendritic cells, and natural killer cells, but also bronchial epithelial cells. Recent studies report that TARC and MDC may serve as pivotal chemokines for the development of Th2-dominated experimental allergen-induced asthma. This study was designed to assess TARC and MDC production by CD4+ T cells, including naive T cells and memory/effector T cells, purified from peripheral blood mononuclear cells in patients with asthma. Asthmatic subjects included in this study had mild asthmatic symptoms, positive skin test responses to house dust mite allergen, and elevated level of Dermatophagoides farinae immunoglobulin E in the sera. CD4+ T cells--CD45RA+ CD4+ T cells--as naive T cells and CD45RO+ CD4+ T cells--as memory/effector T cells--were purified by negative selection from peripheral blood mononuclear cells obtained from asthmatic patients (n = 6) and healthy controls (n = 6). These cells and established Th1/Th2 cell lines were then cultured in the presence of both anti-CD3 and -CD28 antibodies. After 48 hr of incubation, concentrations of TARC, MDC, interleukin (IL)-4, IL-5, and interferon-gamma in the supernatants were measured by enzyme-linked immunoadsorbent assay. Reverse transcriptase-polymerase chain reaction was performed to analyze mRNA expression of TARC and MDC. Our results clearly showed that TARC and MDC were produced by activated CD45RA+ CD4+ T cells rather than by activated CD45RO+ CD4+ T cells, and the levels of these chemokines in the asthmatic patients were higher than those in the healthy controls. Furthermore, these chemokines production by Th2 cell lines were greater than those by Th1 cell lines, but the level were smaller than those by naive T cells. Our studies suggest that TARC and MDC are produced by naive T cells rather than by memory/effector T cells, including Th2 cells, in asthmatic patients, and these chemokines were produced at modest levels in any T-cell populations from healthy controls. Taken together, naive T cells in asthma have a peculiar function to produce TRAC and MDC, which contribute to local migration of Th2 cells into lung and lymphoid tissues, along with a function as precursor for memory/effector T cell. This novel function of naive T cells may be implicated in the development of asthma.

Anti-interleukin-9 antibody treatment inhibits airway inflammation and hyperreactivity in mouse asthma model

Numerous in vitro and in vivo studies in both animals and patients with asthma have shown that interleukin (IL)-9 is an important inflammatory mediator in asthma. To examine the effects of IL-9 antagonism on airway inflammation, ovalbumin-sensitized BALB/c mice were intravenously given anti-IL-9 antibody or an isotype-matched control antibody 30 minutes before challenge with aerosolized ovalbumin. Airway response to methacholine was measured, and samples of bronchoalveolar lavage fluid (BALF) were obtained 24 hours after the last antigen challenge. Lung tissue was harvested and examined histopathologically. After ovalbumin challenge, there were significant increases in airway hyperreactivity, the numbers of inflammatory cells in lung, and IL-4, IL-5, and IL-13 production in BALF. Treatment with anti-IL-9 antibody significantly prevented airway hyperreactivity in response to methacholine inhalation. Blockade of IL-9 reduced the numbers of eosinophils (0.3 +/- 0.1 x 10(5) and 23.6 +/- 0.5 x 10(5)/ml, anti-IL-9 antibody/control immunoglobulin G) and lymphocytes (0.2 +/- 0.2 x 10(5) and 0.8 +/- 0.1 x 10(5)/ml) in BALF. Anti-IL-9 antibody treatment also reduced the concentrations of IL-4 (from 70.6 +/- 4.6 to 30.8 +/- 5.2 pg/ml), IL-5 (from 106.4 +/- 12 to 54.4 +/- 6.6 pg/ml), and IL-13 (from 44.2 +/- 7.6 to 30.1 +/- 5.5 pg/ml) in BALF. Macrophage-derived cytokine expression in the airways was also decreased by IL-9 blockade. Taken together, our findings emphasize the importance of IL-9 in the pathogenesis of asthma and suggest that blockade of IL-9 may be a new therapeutic strategy for bronchial asthma.

A putative silencer element in the IL-5 gene recognized by Bcl6

The Bcl6 gene is ubiquitously expressed in adult murine tissues and its product functions as a sequence-specific transcriptional repressor. Bcl6-deficient mice displayed eosinophilic inflammation caused by overproduction of Th2 cytokines. The regulatory mechanism of those cytokine productions by Bcl6 is controversial. When CD4(+) T cells from Bcl6-deficient and lck-Bcl6-transgenic mice were stimulated with anti-CD3 Abs, production of IL-5 among Th2 type cytokines was preferentially affected by the amount of Bcl6 in the T cells. We found a putative Bcl6-binding sequence (IL5BS) on the 3' untranslated region in the murine and human IL-5 genes, and specific binding of Bcl6 protein to the sequence was confirmed by gel retardation assay and chromatin immunoprecipitation assay. The binding activity of endogenous Bcl6 was transiently diminished in Th2 but not in Th1 clones after anti-CD3 stimulation. The exogenous Bcl6 repressed expression of the reporter gene with the IL5BS in K562 cells and the repressor activity was lost by a point mutation of the IL5BS. Furthermore, the IL5BS was required for Bcl6 to repress expression of the IL-5 cDNA. Thus, the IL5BS may act as a silencer element for Bcl6 to repress expression of the IL-5 gene.

Role for Bcl-6 in the generation and maintenance of memory CD8+ T cells

Naïve T cells proliferate and differentiate into memory cells after antigenic stimulation or in a lymphopenic environment. We showed here transient increases in memory phenotype CD8+ T cell numbers in the lymphopenic environment of spleens of very young mice. The magnitude of the increase correlated with Bcl-6 expression in the T cells. Bcl-6 controlled the generation and maintenance of antigen-specific memory phenotype CD8+ T cells in the spleens of immunized mice. These data suggest that Bcl-6, which is essential for memory B cell development in germinal centers, is a key molecule for the establishment not only of memory T cells but also of the peripheral T cell compartment in infancy.

A549 cells can express interleukin-16 and stimulate eosinophil chemotaxis

Alveolar epithelial cells produce many types of chemokines such as regulated on activation, normal T cells expressed and secreted (RANTES), eotaxin induced by interleukin (IL)-1 beta, or tumor necrosis factor (TNF)-alpha and may contribute to allergic disease by recruiting eosinophils. However, identification of the eosinophil chemotacic activity (ECA) release from A549 cells, an alveolar type II cell line, has not yet been completed. Recently, IL-16 was also reported to be a potent chemotactic stimulus for CD4(+) T lymphocytes and eosinophils in asthma and other pulmonary diseases. To test the possibility that alveolar epithelial cells produce IL-16, we analyzed RNA and culture supernatant from A549 cells by reverse transcription/ polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). The release of ECA from A549 cells was assessed using a blind-well chemotactic chamber. IL-16 release was increased in a concentration-dependent manner by stimulation with IL-1 beta or TNF-alpha. A549 cells also expressed IL-16 messenger RNA. The combination of IL-4 and IL-1 beta or TNF-alpha had an additive effect on IL-16 production. The release of ECA was induced by IL-1 beta or TNF-alpha in a dose-dependent manner. The combination of these cytokines had a greater effect than one alone. The blockade of eotaxin and IL-16 caused 70% inhibition of ECA, but anti-RANTES antibodies only caused 30% inhibition and anti-IL-8 antibodies failed to affect inhibition. These findings suggest a role for chemokines released by alveolar epithelial cells in the recruitment of eosinophils into the lung in pulmonary disorders such as asthma and interstitial lung diseases, and suggested that eotaxin and IL-16 are potent and effective eosinophil chemoattractants.

Binding of BAZF and Bc16 to STAT6-binding DNA sequences

BAZF, a family member of Bcl6, can function as a sequence-specific transcriptional repressor. We determined BAZF-binding DNA sequence. The consensus binding sequence (CBS) of BAZF is almost the same as those of Bcl6 previously described. Three nucleotides of T, G and A at position 6, 8, and 9 in the CBS (5'-ATTCCTAGAAAG-3') are important nucleotides for binding of both BAZF and Bcl6. Since a part (5'-TTC-CTA-GAA-3') of the CBS resembled the sequence motif (5'-TTC-(N3-4)-GAA-3') bound by STAT factors, BAZF and Bcl6 can bind to the CD23b-STAT6-binding sequence (5'-TTTC-TTA-GAAAT-3'), the immunoglobulin germline epsilon-STAT6-binding sequence (5'-CTTC-CCAA-GAAC-3'), and the IL4-STAT6-binding sequence (5'-TTTC-CCA-GAAAA-3') with weak affinity. However, a mutation of C nucleotide to T nucleotide in the IL4-STAT6-binding sequence (5'-TTTC-CTA-GAAAA-3') strongly increased the binding activity of BAZF and Bcl6. These results suggest that BAZF and Bcl6 can repress some of STAT-induced transcription by binding to DNA sequences recognized by STAT factors.

Recurrence of myocarditis presenting as pacing and sensing failure after implantation of a permanent pacemaker at first onset

A 31-year-old woman was admitted to hospital with loss of consciousness and generalized convulsions. Electrocardiography (ECG) showed complete atrioventricular block (AV block) with a pulse rate of 30 beats/min. Endomyocardial biopsy from the right ventricle showed massive necrosis and degeneration of myocardial cells with extensive infiltration of lymphocytes into the interstitial space. These pathological findings suggested fulminant myocarditis. Following glucocorticoid therapy, the patient became asymptomatic, but the AV block did not resolve completely and a bifocal pacemaker was implanted. However, similar symptoms recurred 7 years later. An ECG showed pacing and sensing failure linked to an increase in the pacing threshold and a decrease in the sensing threshold. Endomyocardial biopsy from the right ventricle again showed interstitial infiltration with lymphocytes and eosinophils. After glucocorticoid therapy, she became asymptomatic once more, and the improvement in the pacing and sensing failure, and cardiomegaly, was satisfactory. This patient represents a very rare case of recurrence of acute myocarditis without progression, as much as 7 years after its first occurrence. Glucocorticoid therapy was still effective in treating the recurrent myocarditis presenting with pacing and sensing failure.