Intestinal epithelial culture under an air-liquid interface: a tool for studying human and mouse esophagi.

This study investigated whether an intestinal epithelial culture method can be applied to mouse and human esophageal cultures. The esophagi harvested from 1-day-old mice and adult humans were maintained in collagen gels. A commercially available culture medium for human embryonic stem cells was used for the human esophageal culture. We discovered that the intestinal epithelial culture method can be successfully applied to both mouse and human esophageal cultures. The long-term cultured esophageal organoids were rod-like luminal structures lined with myofibroblasts. We discovered that regeneration of the esophageal mucosal surface can be almost completely achieved in vitro, and the advantage of this method is that organoid cultures may be generated using host-derived fibroblasts as a niche. This method is a promising tool for mouse and human research in intestinal biology, carcinogenesis, and regenerative medicine.

Concurrent analysis of human equilibrative nucleoside transporter 1 and ribonucleotide reductase subunit 1 expression increases predictive value for prognosis in cholangiocarcinoma patients treated with adjuvant gemcitabine-based chemotherapy.

BACKGROUND: The aim of this study was to investigate the predictive and prognostic values of intratumoural human equilibrative nucleoside transporter 1 (hENT1) and ribonucleotide reductase subunit 1 (RRM1) expression in advanced cholangiocarcinoma patients treated with adjuvant gemcitabine-based chemotherapy (AGC). METHODS: Intratumoural hENT1 and RRM1 expression levels were investigated immunohistochemically in 127 patients with advanced cholangiocarcinoma who underwent surgical resection (68 with AGC and 59 without AGC). The impacts of hENT1 and RRM1 expression on survival were evaluated. RESULTS: High intratumoural hENT1 and RRM1 expression levels were observed in 86 (68%) and 67 (53%) patients, respectively. In a multivariate analysis of 68 patients who received AGC, high hENT1 (P=0.044) and low RRM1 expression (P=0.009) were independently associated with prolonged disease-free survival (DFS), whereas low RRM1 expression (P=0.024) was independently associated with prolonged overall survival (OS). Moreover, concurrent high hENT1 and low RRM1 expression was a powerful independent predictor of prolonged DFS (P<0.001) and OS (P=0.001) when the combined classification of hENT1 and RRM1 was introduced. CONCLUSIONS: Concurrent analysis of hENT1 and RRM1 expression may increase the predictive value of these biomarkers for survival of advanced cholangiocarcinoma patients treated with AGC.

Amplification of PVT-1 is involved in poor prognosis via apoptosis inhibition in colorectal cancers.

BACKGROUND: We previously conducted gene expression microarray analyses to identify novel indicators for colorectal cancer (CRC) metastasis and prognosis from which we identified PVT-1 as a candidate gene. PVT-1, which encodes a long noncoding RNA, mapped to chromosome 8q24 whose copy-number amplification is one of the most frequent events in a wide variety of malignant diseases. However, PVT-1 molecular mechanism of action remains unclear. METHODS: We conducted cell proliferation and invasion assays using colorectal cancer cell lines transfected with PVT-1siRNA or negative control siRNA. Gene expression microarray analyses on these cell lines were also carried out to investigate the molecular function of PVT-1. Further, we investigated the impact of PVT-1 expression on the prognosis of 164 colorectal cancer patients by qRT-PCR. RESULTS: CRC cells transfected with PVT-1 siRNA exhibited significant loss of their proliferation and invasion capabilities. In these cells, the TGF-ß signalling pathway and apoptotic signals were significantly activated. In addition, univariate and multivariate analysis revealed that PVT-1 expression level was an independent risk factor for overall survival of colorectal cancer patients. CONCLUSION: PVT-1, which maps to 8q24, generates antiapoptotic activity in CRC, and abnormal expression of PVT-1 was a prognostic indicator for CRC patients.

Transcriptional CCND1 expression as a predictor of poor response to neoadjuvant chemotherapy with trastuzumab in HER2-positive/ER-positive breast cancer.

Several trials have confirmed that the pathological complete response (pCR) rates after neoadjuvant chemotherapy (NAC) are significantly lower in HER2-positive/ER-positive patients than in HER2-positive/ER-negative patients. To understand this phenomenon, we investigated the association between NAC resistance and CCND1, which is frequently overexpressed in ER-positive tumors. Pretreatment formalin-fixed tumor tissues were collected from 75 HER2-positive patients receiving NAC comprised anthracyclines, taxanes, and trastuzumab. Seventeen gene transcripts along with PIK3CA mutations were detected using MassARRAY (Sequenom, San Diego, CA). The gene expression levels were dichotomized according to the median values. The immunohistochemical expression of ER, PTEN, BCL-2, and cyclin D1 was scored. The relationship between the variables was assessed using the Spearman correlation. A logistic regression analysis was performed to detect predictors of pCR, which was defined as no invasive tumor in the breast or axilla. Forty-seven percent of the cases were ER-positive and 52 % (40/63 % in ER-positive/ER-negative) achieved a pCR. Among the ER-positive patients, the CCND1 gene expression level was 2.1 times higher than that in ER-negative patients and was significantly correlated with the expression of cyclin D1 protein. In a univariate analysis, a pCR was associated with high mRNA levels of ESR1, PGR, LMTK3, HER2, IGF1R, INPP4B, PDL-1, BCL-2, and CCND1 (P ≤ 0.05). In contrast, none of these genes were significantly correlated with a pCR among the ER-negative tumors and only EGFR was significantly correlated with a pCR. PIK3CA mutations or PTEN loss were not associated with a pCR in either group. After excluding ESR1 (r = 0.58), PGR (r = 0.64), and IGF1R (r = 0.59), the expressions of which were correlated with CCND1, a multivariate analysis revealed that CCND1 [P = 0.043; OR, 0.16] and HER2 [P = 0.012; OR, 11.2] retained its predictive value for pCR among ER-positive patients, but not among ER-negative patients. A High Level of CCND1 gene expression is a poor predictor of a pCR and provides a rationale for evaluating CDK4/6 inhibitors in HER2-positive/ER-positive breast cancer patients.

PICT1 regulates TP53 via RPL11 and is involved in gastric cancer progression.

BACKGROUND: The TP53 pathway is frequently inactivated in human cancers. PICT1 (also known as GLTSCR2) is a novel regulator of the MDM2-TP53 pathway via its interaction with the ribosomal protein RPL11 in the nucleolus. However, the clinical significance of PICT1 in gastric cancer remains unknown. METHODS: To evaluate PICT1 function, we used shRNA to inhibit PICT1 expression in gastric cancer cells that expressed wild-type TP53. PICT1 expression and TP53 mutation status were quantified in 110 cases of primary gastric cancer to explore the impact of PICT1 expression levels on gastric cancer. RESULTS: Deficiency of PICT1 significantly impaired cell proliferation and colony formation via TP53-mediated cell cycle arrest. Following induction of PICT1 deficiency, RPL11 translocated out of the nucleolus. Of the 110 gastric cancer samples tested, 70 (63.6%) and 40 (36.4%) tumours expressed wild-type and mutant TP53, respectively. In gastric cancer patients with wild-type TP53 tumours, patients with relatively low PICT1 expression levels had a better prognosis compared with high expression level patients (P=0.046). CONCLUSION: The findings suggest that PICT1 has a crucial role in gastric cancer progression by regulating the MDM2-TP53 pathway through RPL11. Clinically, PICT1 expression is a novel prognostic parameter in gastric cancer patients with wild-type TP53 tumours.

Paired related homoeobox 1, a new EMT inducer, is involved in metastasis and poor prognosis in colorectal cancer.

BACKGROUND: Paired related homoeobox 1 (PRRX1) has been identified as a new epithelial-mesenchymal transition (EMT) inducer in breast cancer. However, the function of PRRX1 in colorectal cancer (CRC) has not been elucidated. METHODS: We utilised ectopic PRRX1-expressing cell lines to analyse the function of PRRX1 in CRC. The clinical significance of PRRX1 was also examined on three independent CRC case sets. RESULTS: PRRX1 induced EMT and the stem-like phenotype in CRC cells. In contrast to studies of breast cancer, abundant expression of PRRX1 was significantly associated with metastasis and poor prognosis in CRC. CONCLUSION: PRRX1 is an indicator of metastasis and poor prognosis in CRC cases. Further investigation is required to uncover the signalling network regulating PRRX1.

An endoscopic hydro-mastoidectomy technique for cholesteatoma surgery.

OBJECTIVE: Endoscopic hydro-mastoidectomy, in which mastoidectomy is performed underwater, can be employed during transcanal endoscopic ear surgery for cholesteatoma removal. It was hypothesised that endoscopic hydro-mastoidectomy might take less time than endoscopic non-underwater mastoidectomy because the endoscope does not need to be removed for cleaning. METHODS: This study compared the mastoidectomy and total operative durations between the endoscopic hydro-mastoidectomy (n = 25) and endoscopic non-underwater drilling (control, n = 8) groups. Moreover, it compared the size of resected areas of the external auditory canal between the two groups. RESULTS: The mastoidectomy time of the endoscopic hydro-mastoidectomy group was significantly shorter than that of the control group (p < 0.01). The total operative time did not differ significantly between the endoscopic hydro-mastoidectomy and control groups (p = 0.17). The resected area was significantly larger in the endoscopic hydro-mastoidectomy group than in the control group (p < 0.05). CONCLUSION: Endoscopic hydro-mastoidectomy enables more extensive bone resection within a shorter period.

Temperature distributions of electron beam-irradiated samples by scanning electron microscopy.

An electron beam (EB) generated by a scanning electron microscope (SEM) was used to irradiate two samples having different thermal conductivities, and the resulting temperatures of the EB-irradiated areas as well as the temperature distributions within the samples were then measured using a thermal camera. These measurements showed overall increases in sample temperatures, as well as revealed temperature rises at the EB-irradiated areas that had little difference with one of the theoretical predictions. Differences between the actual and the predicted temperature measurements were analysed in terms of the accuracy with which parameters could be estimated. The temperature distributions of the samples were measured and, On the basis of the results, it was hypothesized that the temperature differential over an irradiated sample will be inversely correlated with its thermal conductivity.

Phenotype Harmonization in the GLIDE2 Oral Health Genomics Consortium.

Genetic risk factors play important roles in the etiology of oral, dental, and craniofacial diseases. Identifying the relevant risk loci and understanding their molecular biology could highlight new prevention and management avenues. Our current understanding of oral health genomics suggests that dental caries and periodontitis are polygenic diseases, and very large sample sizes and informative phenotypic measures are required to discover signals and adequately map associations across the human genome. In this article, we introduce the second wave of the Gene-Lifestyle Interactions and Dental Endpoints consortium (GLIDE2) and discuss relevant data analytics challenges, opportunities, and applications. In this phase, the consortium comprises a diverse, multiethnic sample of over 700,000 participants from 21 studies contributing clinical data on dental caries experience and periodontitis. We outline the methodological challenges of combining data from heterogeneous populations, as well as the data reduction problem in resolving detailed clinical examination records into tractable phenotypes, and describe a strategy that addresses this. Specifically, we propose a 3-tiered phenotyping approach aimed at leveraging both the large sample size in the consortium and the detailed clinical information available in some studies, wherein binary, severity-encompassing, and "precision," data-driven clinical traits are employed. As an illustration of the use of data-driven traits across multiple cohorts, we present an application of dental caries experience data harmonization in 8 participating studies (N = 55,143) using previously developed permanent dentition tooth surface-level dental caries pattern traits. We demonstrate that these clinical patterns are transferable across multiple cohorts, have similar relative contributions within each study, and thus are prime targets for genetic interrogation in the expanded and diverse multiethnic sample of GLIDE2. We anticipate that results from GLIDE2 will decisively advance the knowledge base of mechanisms at play in oral, dental, and craniofacial health and disease and further catalyze international collaboration and data and resource sharing in genomics research.

The indications for a diverting stoma in low anterior resection for rectal cancer: a prospective multicentre study of 222 patients from Japanese cancer centers.

AIM: The aim of the study was to determine the present state of diverting stoma construction in Japanese cancer centres and to investigate the relationship between symptomatic leakage and diverting stoma after low anterior resection for rectal cancer. METHOD: Two hundred and twenty-two consecutive patients undergoing low anterior resection for rectal cancer located within 10 cm from the anal verge were investigated in a prospective, multicenter study. RESULTS: The overall leakage rate was 9.0% (20/222). Of 31 cases with an anastomosis within 2.0 cm from the anal verge, 22 (71%) had a diverting stoma. Of cases anastomosed within 5.0 cm, the absence of a diverting stoma and tumour size were significantly related to an increased rate of leakage [leakage in 13 (12.7%) of 102 cases without a diverting stoma; in three (3.8%) of 80 cases with a diverting stoma]. Among anastomoses within 2.0 cm from the anal verge, leakage occurred in four (44.4%) of nine cases without and in none (0%) of 22 cases with a diverting stoma. CONCLUSION: We recommend a diverting stoma for an anastomosis within 5.0 cm of the anal verge and strongly recommend it for a very low anastomosis within 2.0 cm.

Differentiation in vitro of T3+ large granular lymphocytes with characteristic cytotoxic activity from an isolated hematopoietic progenitor colony.

Blast colonies were developed by rIL-3 from the spleen cells of mice pretreated with 5-fluorouracil (5-FU) in the methylcellulose cultures. When such IL-3-induced blast colonies were individually lifted up and recultured in the presence of rIL-3 and recombinant erythropoietin (rEpo), a variety of hematopoietic colonies developed from every single colony, including neutrophils, macrophages, eosinophils, megakaryocytes, mast cells, and erythroblasts. The results indicated that IL-3-induced blast colonies consisted of multipotential hematopoietic progenitor cells. By culturing individual IL-3-induced blast colonies in the presence of rIL-2 and irradiated peritoneal macrophages, on the other hand, the proliferation of homogeneous lymphoid cells was observed in 5 of 24 wells, each of which received a single blast colony. Morphologically, they were typical large granular lymphocytes (LGL), and thus it was indicated that LGL could be differentiated directly from the hematopoietic progenitor cells utterly in vitro by rIL-2 and accessory macrophages. From one of these culture wells, a continuous LGL line, IL3B1, was successfully obtained. The proliferation of IL3B1 was dependent on IL-2 in the presence of accessory macrophages, but they no longer responded to IL-3, nor to another T cell growth factor, IL-4. Flow cytometric analysis indicated that the phenotype of IL3B1 was Thy-1+,T3+,L3T4-,Lyt-2-,T200+ Asialo GM1+, whereas that of original IL-3-induced blast cells was Thy-1+,T3-,L3T4-,Lyt-2-,B220-. The results suggested that the expression of T3 molecules was induced in the process of LGL differentiation from the hematopoietic progenitor cells in vitro. Conforming to this, it was revealed that both gamma and beta chain genes of the TCR were rearranged in IL3B1. Northern blot analysis indicated that IL3B1 had abundant mRNA for gamma chain, while mRNA for beta chain was rather faint. Functionally, IL3B1 exhibited typical NK-patterned cytotoxic activity against a panel of tumor cell targets. In addition, they showed significant cytotoxic activity against normal bone marrow cells, as well as various factor-dependent myelogenous progenitor cell lines, all of which were resistant to endogenous NK activity of the fresh spleen cells. These results indicated that at least a set of T3+ LGL with rearranged TCR genes could be directly differentiated from isolated hematopoietic progenitor cells in vitro. Results also suggested that such a prethymically differentiated subset of T-lineage lymphocytes, namely T3+ double-negative LGL, had particular cytotoxic activity in addition to conventional NK activity, which might well contribute to feedback regulation of hematopoiesis.

Generation of continuous large granular lymphocyte lines by interleukin 2 from the spleen cells of mice infected with Moloney leukemia virus. Involvement of interleukin 3.

Continuous cell lines could be reproducibly established by culturing spleen cells from adult mice injected with MLV-producer cells or directly infected with Mo-MLV with rIL-2, whereas the culture of normal splenic cells with rIL-2 induced only transient and limited proliferation resulting in no such lines. All of the lines showed morphological characteristics as LGL with Thy-1+,Lyt-1-,L3T4-,Lyt-2-,AsGM1+,FcR gamma+ phenotype without exception, and most of them exhibited typical NK-patterned cytotoxicity. Analysis of reverse transcriptase activity of the culture supernatants as well as Southern hybridization of the DNA from the lines using an Mo-MLV-specific cDNA probe indicated no evidence of retroviral replication or proviral integration, suggesting that the generation of cell lines reflected a reactive process and viral infection was not directly responsible. It was subsequently revealed that Thy-1+,Lyt-1+,Lyt-2- spleen cells from mice infected with Mo-MLV in vivo spontaneously produced surprising amounts of IL-3 in vitro, leading to the possibility that IL-3 was responsible for the generation of lines. The possibility was directly supported by the observation that continuous lines with identical characteristics could be generated completely in vitro by sequential stimulation with rIL-3 and rIL-2 from normal spleen cells without any involvement of Mo-MLV. The C beta gene of TCR was shown to be rearranged in all the lines examined, indicating the LGL lines were all genetically committed to T cell lineage. Unlike the situation in normal splenic populations expanded by rIL-2, where the expression of IL-2-R was progressively lost, constitutive expression of high-affinity-IL-2-R was observed in all the lines and thus, this was considered to explain the unlimited proliferation of them in response to rIL-2 alone. These results suggested the probable role of IL-3 in the regulation of growth and differentiation of a set of LGL committed to T cell lineage. The possible implications of the phenomenon in the regulation of hematopoiesis as well as in the control of Mo-MLV-induced leukemogenesis were discussed.

Functional interaction between human histocompatibility leukocyte antigen (HLA) class II and mouse CD4 molecule in antigen recognition by T cells in HLA-DR and DQ transgenic mice.

Studies in vitro have suggested that a species barrier exists in functional interaction between human histocompatibility leukocyte antigen (HLA) class II and mouse CD4 molecules. However, whether mouse CD4+ T cells restricted by HLA class II molecules are generated in HLA class II transgenic mice and respond to peptide antigens across this barrier has remained unclear. In an analysis of T cell responses to synthetic peptides in mice transgenic for HLA-DR51 and -DQ6, we found that DR51 and DQ6 transgenic mice acquired significant T cell response to influenza hemagglutinin-derived peptide 307-319 (HA 307) and Streptococcus pyogenes M12 protein-derived peptide 347-397 (M6C2), respectively. Inhibition studies with several monoclonal antibodies showed that transgenic HLA class II molecules presented these peptides to mouse CD4+ T cells. Furthermore, T cell lines specific for HA 307 or M6C2 obtained from the transgenic mice could respond to the peptide in the context of relevant HLA class II molecules expressed on mouse L cell transfectants that lack the expression of mouse MHC class II. These findings indicate that interaction between HLA class II and mouse CD4 molecules is sufficient for provoking peptide-specific HLA class II-restricted T cell responses in HLA class II transgenic mice.

A recombinant murine granulocyte/macrophage (GM) colony-stimulating factor derived from an inducer T cell line (IH5.5). Functional restriction to GM progenitor cells.

The cDNA for the murine granulocyte/macrophage colony-stimulating factor (GM-CSF) was cloned from a cDNA library obtained from a murine T cell line, IH5.5, by using two synthetic probes that encoded two parts of the GM-CSF from murine lung. The cDNA inserted into the plasmid vector pcDV1 was transfected into monkey COS-1 cells and the conditioned medium was used to investigate the hemopoietic activities of the resultant product, recombinant GM-CSF (rGM-CSF), by means of various colony assays. rGM-CSF stimulated only neutrophil/macrophage colonies in the cultures of murine normal bone marrow and fetal liver cells. No other colony stimulating activities (CSA) were seen in the preparation including burst-promoting activity, eosinophil-CSA, megakaryocyte-CSA and mast cell-CSA. rGM-CSF could not support colony formation of 5-fluorouracil-treated mouse spleen cells, in which only the primitive population of stem cells survived. However, after culture of these cells with PWM-spleen cell-conditioned medium (PWM-SCM), the colonies consisting of blast cells were formed. These blast cells could now be induced to form neutrophil/macrophage colonies in the presence of rGM-CSF. Pure neutrophil colonies, pure macrophage colonies, as well as mixed neutrophil/macrophage colonies, were formed from these single blast cells in the presence of rGM-CSF by micromanipulation. rGM-CSF did not act on pluripotent hemopoietic stem cells, but did act directly and selectively on neutrophil/macrophage progenitors. Moreover, striking heterogeneities were noted in the size of the colonies and the proportion of components. GM-CSF is, therefore, considered to play a noninstructive role in the differentiation of the GM pathway.

Identification of proliferating dendritic cell precursors in mouse blood.

While it has been known that dendritic cells arise from proliferating precursors in situ, it has been difficult to identify progenitors in culture. We find that aggregates of growing dendritic cells develop in cultures of mouse blood that are supplemented with granulocyte/macrophage colony-stimulating factor (GM-CSF) but not other CSFs. The dendritic cell precursor derives from the Ia-negative and nonadherent fraction. The aggregates of developing dendritic cells appear at about 1 wk of culture, with 100 or more such clusters being formed per 10(6) blood leukocytes. The aggregates can be dislodged and subcultured as expanding clusters that are covered with cells having the motile sheet-like processes ("veils") of dendritic cells. By about 2 wk, large numbers of single, major histocompatibility complex (MHC) class II-rich dendritic cells begin to be released into the medium. Combined immunoperoxidase and [3H]thymidine autoradiography show that the cells that proliferate within the aggregate lack certain antigenic markers that are found on mature dendritic cells. However, in pulse-chase protocols, the [3H]thymidine-labeled progeny exhibit many typical dendritic cell features, including abundant MHC class II and a cytoplasmic granular antigen identified by monoclonal antibody 2A1. The progeny dendritic cells are potent stimulators of the mixed leukocyte reaction and can home to the T-dependent areas of lymph node after injection into the footpads. We conclude that mouse blood contains GM-CSF-dependent, proliferating progenitors that give rise to large numbers of dendritic cells with characteristic morphology, mobility, phenotype, and strong T cell stimulatory function.

Commitment and differentiation of osteoclast precursor cells by the sequential expression of c-Fms and receptor activator of nuclear factor kappaB (RANK) receptors.

Osteoclasts are terminally differentiated cells derived from hematopoietic stem cells. However, how their precursor cells diverge from macrophagic lineages is not known. We have identified early and late stages of osteoclastogenesis, in which precursor cells sequentially express c-Fms followed by receptor activator of nuclear factor kappaB (RANK), and have demonstrated that RANK expression in early-stage of precursor cells (c-Fms(+)RANK(-)) was stimulated by macrophage colony-stimulating factor (M-CSF). Although M-CSF and RANKL (ligand) induced commitment of late-stage precursor cells (c-Fms(+)RANK(+)) into osteoclasts, even late-stage precursors have the potential to differentiate into macrophages without RANKL. Pretreatment of precursors with M-CSF and delayed addition of RANKL showed that timing of RANK expression and subsequent binding of RANKL are critical for osteoclastogenesis. Thus, the RANK-RANKL system determines the osteoclast differentiation of bipotential precursors in the default pathway of macrophagic differentiation.

Expression and function of c-kit in hemopoietic progenitor cells.

The expression and function of a receptor tyrosine kinase, c-kit, in the adult bone marrow of the mouse were investigated by using monoclonal antibodies (mAbs) against the extracellular domain of murine c-kit. In adult C57BL/6 mouse, 7.8% of total bone marrow cells express c-kit on their surface. Half of the c-kit+ cells do not express lineage markers including Mac-1, Gr-1, TER-119, and B220, while the remainder coexpress myeloid lineage markers such as Mac-1 and Gr-1. After c-kit+ cells were removed from the bone marrow cell preparation, hemopoietic progenitor cells reactive to IL-3, GM-CSF, or M-CSF and also those which give rise to spleen colonies in irradiated recipients disappeared almost completely. Thus, most hemopoietic progenitors in the adult bone marrow express c-kit. To investigate whether or not c-kit has any role in the hemopoiesis of adult bone marrow, we took the advantage of one of the anti-c-kit mAbs that can antagonize the function of c-kit. As early as two days after the injection of 1 milligram of an antagonistic antibody, ACK2, almost all hemopoietic progenitor cells disappeared from the bone marrow, which eventually resulted in the absence of mature myeloid and erythroid cells in the bone marrow. These results provide direct evidence that c-kit is an essential molecule for constitutive intramarrow hemopoiesis, especially for the self-renewal of hemopoietic progenitor cells at various stages of differentiation.

Stepwise progression of B lineage differentiation supported by interleukin 7 and other stromal cell molecules.

Growth of early B precursor cells was investigated in vitro by using rIL-7 and IL-7-defective stromal cell line PA6 as separate growth signals. B cell development proceeds through three sequential stages different from the growth signal requirement. The cells in the first stage require PA6 alone for the proliferation, and differentiate into the second stage, which requires both PA6 and IL-7 for its growth. When IL-7 is available for the cells in the second stage, they proliferate extensively on the PA6 layer, and some acquire the ability to proliferate in response to IL-7 alone. This sequential change of growth signal requirement, however, does not proceed autonomously along the time schedule. The possibility that it is primarily directed by the result of Ig gene rearrangement is considered. This mode of growth control may explain why only functional B cells are selected in the error-prone process of Ig gene rearrangement during B lineage differentiation.

Interleukin 7 production and function in stromal cell-dependent B cell development.

The role of IL-7 in the stromal cell-dependent B cell development was investigated using two stromal cell clones, ST2 and PA6; the former supports B lymphopoiesis while the latter can not. We demonstrate here that: (a) the ability of the stromal cell clone to produce IL-7 correlates well with the stromal cell activity to support B lymphopoiesis; (b) IL-7 production by ST2 is inducible rather than constitutive; (c) the IL-7-dependent B cell itself is a potent inducer of IL-7 production by ST2; (d) addition of rIL-7 to the PA6 layer renders this in vitro environment B lymphopoietic; and (e) the differentiation from early B progenitor to pre-B cell requires both IL-7 and other stromal cell molecule(s) yet to be identified.