A respiratory chain controlled signal transduction cascade in the mitochondrial intermembrane space mediates hydrogen peroxide signaling.

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) govern cellular homeostasis by inducing signaling. H2O2 modulates the activity of phosphatases and many other signaling molecules through oxidation of critical cysteine residues, which led to the notion that initiation of ROS signaling is broad and nonspecific, and thus fundamentally distinct from other signaling pathways. Here, we report that H2O2 signaling bears hallmarks of a regular signal transduction cascade. It is controlled by hierarchical signaling events resulting in a focused response as the results place the mitochondrial respiratory chain upstream of tyrosine-protein kinase Lyn, Lyn upstream of tyrosine-protein kinase SYK (Syk), and Syk upstream of numerous targets involved in signaling, transcription, translation, metabolism, and cell cycle regulation. The active mediators of H2O2 signaling colocalize as H2O2 induces mitochondria-associated Lyn and Syk phosphorylation, and a pool of Lyn and Syk reside in the mitochondrial intermembrane space. Finally, the same intermediaries control the signaling response in tissues and species responsive to H2O2 as the respiratory chain, Lyn, and Syk were similarly required for H2O2 signaling in mouse B cells, fibroblasts, and chicken DT40 B cells. Consistent with a broad role, the Syk pathway is coexpressed across tissues, is of early metazoan origin, and displays evidence of evolutionary constraint in the human. These results suggest that H2O2 signaling is under control of a signal transduction pathway that links the respiratory chain to the mitochondrial intermembrane space-localized, ubiquitous, and ancient Syk pathway in hematopoietic and nonhematopoietic cells.

CD200 flow cytometric assessment and semiquantitative immunohistochemical staining distinguishes hairy cell leukemia from hairy cell leukemia-variant and other B-cell lymphoproliferative disorders.

OBJECTIVES: To evaluate CD200 expression in B-cell proliferative disorders. METHODS: We analyzed 180 recent specimens of B-cell neoplasms for CD200 expression by flow cytometric immunophenotypic analysis, which is better able to assess relative intensity of staining than immunohistochemical staining. RESULTS: We found that hairy cell leukemia exhibits a high level of staining for CD200 in comparison to other B-cell lymphoproliferative disorders, including hairy cell leukemia-variant (HCL-V), marginal zone lymphoma, and lymphoplasmacytic lymphoma. We confirmed this observation by semiquantitative immunohistochemical staining. CONCLUSIONS: Assessment of the CD200 expression level is helpful to distinguish HCL from HCL-V and other B-cell lymphoproliferative disorders and in the differential diagnosis of B-cell neoplasms in general.

Utility of CD200 immunostaining in the diagnosis of primary mediastinal large B cell lymphoma: comparison with MAL, CD23, and other markers.

CD200, an immunoglobulin superfamily membrane glycoprotein, is expressed in a number of B cell lymphoproliferative disorders, including primary mediastinal large B cell lymphoma, but not diffuse large B cell lymphoma, based on a preliminary study. Here, we compare the expression of CD200 with other markers of primary mediastinal large B cell lymphoma, including MAL and CD23, in formalin-fixed, paraffin-embedded histologic sections from a series of 35 cases of primary mediastinal large B cell lymphoma and 30 cases of diffuse large B cell lymphoma. CD200 exhibits the greatest staining sensitivity of the markers studied: 94%, compared with CD23 (69%), MAL (86%), TRAF (86%), and REL (77%). It exhibits staining specificity of 93%, similar to that of CD23 (93%) and MAL (97%), and greater than that of TRAF (77%) and REL (83%). We conclude that CD200 is a practical and useful marker for the diagnosis of primary mediastinal large B cell lymphoma.

Cytoplasmic Ig alpha serine/threonines fine-tune Ig alpha tyrosine phosphorylation and limit bone marrow plasma cell formation.

Igα serine 191 and 197 and threonine 203, which are located in proximity of the Igα ITAM, dampen Igα ITAM tyrosine phosphorylation. In this study, we show that mice with targeted mutations of Igα S191, 197, and T203 displayed elevated serum IgG2c and IgG2b concentrations and had elevated numbers of IgG2c- and IgG2b-secreting cells in the bone marrow. BCR-induced Igα tyrosine phosphorylation was slightly increased in splenic B cells. Our results suggest that Igα serine/threonines limit formation of IgG2c- and IgG2b-secreting bone marrow plasma cells, possibly by fine-tuning Igα tyrosine-mediated BCR signaling.

RUNX transcription factors: association with pediatric asthma and modulated by maternal smoking.

Intrauterine smoke exposure (IUS) is a strong risk factor for development of airways responsiveness and asthma in childhood. Runt-related transcription factors (RUNX1-3) have critical roles in immune system development and function. We hypothesized that genetic variations in RUNX1 would be associated with airway responsiveness in asthmatic children and that this association would be modified by IUS. Family-based association testing analysis in the Childhood Asthma Management Program genome-wide genotype data showed that 17 of 100 RUNX1 single-nucleotide polymorphisms (SNPs) were significantly (P < 0.03-0.04) associated with methacholine responsiveness. The association between methacholine responsiveness and one of the SNPs was significantly modified by a history of IUS exposure. Quantitative PCR analysis of immature human lung tissue with and without IUS suggested that IUS increased RUNX1 expression at the pseudoglandular stage of lung development. We examined these associations by subjecting murine neonatal lung tissue with and without IUS to quantitative PCR (N = 4-14 per group). Our murine model showed that IUS decreased RUNX expression at postnatal days (P)3 and P5 (P < 0.05). We conclude that 1) SNPs in RUNX1 are associated with airway responsiveness in asthmatic children and these associations are modified by IUS exposure, 2) IUS tended to increase the expression of RUNX1 in early human development, and 3) a murine IUS model showed that the effects of developmental cigarette smoke exposure persisted for at least 2 wk after birth. We speculate that IUS exposure-altered expression of RUNX transcription factors increases the risk of asthma in children with IUS exposure.

MUC2 is a highly specific marker of goblet cell metaplasia in the distal esophagus and gastroesophageal junction.

Currently, the American College of Gastroenterology requires identification of goblet cells in mucosal biopsies from the esophagus to diagnose Barrett esophagus (BE). Identification of goblet cells in mucosal biopsies is fraught with limitations such as sampling and interpretation error. One previous study by our group suggested that MUC2 expression in esophageal nongoblet columnar cells represents a late biochemical reaction in the conversion of mucinous columnar cells to goblet cells in BE. We conducted this study to evaluate the prevalence, sensitivity, and specificity of MUC2 positivity in nongoblet columnar epithelium for detection of goblet cells in the distal esophagus and gastroesophageal junction (GEJ) region. We also sought to identify associations between MUC2 positivity and clinical and endoscopic risk factors for BE. This analysis utilized mucosal biopsies of the distal esophagus or GEJ from 100 patients who participated in a community clinic-based study of patients with chronic gastroesophageal reflux disease evaluated prospectively in the western part of Washington state. We randomly selected 50 patients who had columnar epithelium with goblet cells, representing the study group and 50 patients without goblet cells, representing the comparison group. Immunohistochemistry for MUC2 was performed on samples in a blinded manner without knowledge of the clinical or endoscopic features of the patients. The presence of staining was noted in both goblet and nongoblet epithelium, both close to and distant from the mucosa with goblet cells, when the latter were present. All study patients showed MUC2 positivity in goblet cells. MUC2 was present in nongoblet columnar epithelium in 78% of study patients with goblet cells, but in only 4% of controls without goblet cells (P<0.0001) (sensitivity, 78%; specificity, 96% for goblet cell metaplasia). MUC2 was significantly more common in nongoblet columnar cells close to, rather than distant from, the mucosa with goblet cells (P<0.00001). Finally, MUC2 was significantly associated with endoscopic evidence of columnar metaplasia in the distal esophagus, and with known risk factors for BE, such as older age, white race, frequent heartburn, and elevated body mass index. We conclude that goblet cells likely develop from a field of MUC2-positive mucinous columnar cells, and as such, MUC2 represents a late event in the development of goblet cells. MUC2 staining in nongoblet columnar cells is a reasonably sensitive and highly specific marker for goblet cells in the distal esophagus and GEJ, and its presence is predictive of endoscopic columnar metaplasia of the esophagus, even in patients without goblet cells.

CD200 (OX-2 membrane glycoprotein) is expressed by follicular T helper cells and in angioimmunoblastic T-cell lymphoma.

CD200, an immunoglobulin superfamily membrane glycoprotein, is expressed in B cells, a subset of T cells, and in a range of B-cell lymphoproliferative disorders. We recently found, by immunohistochemical staining, that follicular helper T cells associated with neoplastic L and H cells in nodular lymphocyte predominant Hodgkin lymphoma, express CD200. Here we show that CD200 is expressed by follicular helper T cells in reactive lymphoid tissue, using single-color and 2-color immunohistochemical staining. Immunohistochemical staining of a range of T-cell lymphoproliferative disorders shows that the neoplastic cells in angioimmunoblastic T-cell lymphoma are immunoreactive for CD200, and the pattern of expression is similar to that of other follicular helper T-cell markers, PD-1 and CXCL13. In contrast, only a minority of cases of T-cell neoplasms other than angioimmunoblastic T-cell lymphoma are immunoreactive for CD200. A subset of CD200-positive peripheral T-cell lymphoma, not otherwise specified, cases may represent evolving angioimmunoblastic T-cell lymphoma or another neoplasm derived from follicular T helper cells. We conclude that CD200 is a useful immunophenotypic marker of angioimmunoblastic T-cell lymphoma and may be a suitable therapeutic target for an anti-CD200 immunotherapy undergoing clinical trial.

CD200 (OX-2 membrane glycoprotein) expression in b cell-derived neoplasms.

We studied the expression of CD200, an immunoglobulin superfamily membrane glycoprotein, in a wide range of B cell-derived neoplasms by immunohistochemical staining of paraffin-embedded tissue sections. In addition to chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), CD200 is expressed in other B-cell lymphoproliferative disorders, including hairy cell leukemia. In addition, neoplastic cells in classical Hodgkin lymphoma are immunoreactive for CD200. CD200 was previously reported to be expressed in acute myeloid leukemia, and we find that it is also expressed in B-lymphoblastic leukemia/lymphoma. We conclude that CD200 may be a useful immunophenotypic marker in the evaluation of B cell-derived neoplasms. Furthermore, since an anti-CD200 immunotherapeutic agent is in clinical trials, a number of B cell-derived neoplasms in addition to CLL/SLL may be suitable therapeutic targets.

The phosphatidylserine receptors, T cell immunoglobulin mucin proteins 3 and 4, are markers of histiocytic sarcoma and other histiocytic and dendritic cell neoplasms.

The T cell immunoglobulin mucin (TIM) proteins are a family of cell surface phosphatidyserine receptors that are important for the recognition and phagocytosis of apoptotic cells. Because TIM-4 is expressed by macrophages and dendritic cells in human tissue, we examined its expression in a range of histiocytic and dendritic cell neoplasms and found moderate to strong immunohistochemical staining in cases of juvenile xanthogranuloma and histiocytic sarcoma, and lower level staining in interdigitating dendritic cell sarcoma, Langerhans cell histiocytosis, acute monocytic leukemia (leukemia cutis), and blastic plasmacytoid dendritic cell neoplasm (hematodermic tumor). TIM-3 was first described on activated T(H)1 cells but was recently shown to also be a phosphatidylserine receptor and mediate phagocytosis. We found TIM-3 was expressed by peritoneal macrophages, monocytes and splenic dendritic cells. We found that it, like TIM-4, is expressed in a range of histiocytic and dendritic cell neoplasms, typically with strong immunohistochemical staining. Cases of diffuse large B cell lymphoma, anaplastic large cell lymphoma, metastatic malignant melanoma, and metastatic poorly differentiated carcinoma generally exhibited negative to minimal heterogenous staining for TIM-4 and TIM-3. We conclude that histiocytic and dendritic cell neoplasms consistently express TIM-3 and TIM-4 and that these molecules are new markers of neoplasms derived from histiocytic and dendritic cells.

Paneth cell differentiation in colonic epithelial neoplasms: evidence for the role of the Apc/beta-catenin/Tcf pathway.

Paneth cell differentiation may occur in colonic epithelial neoplasms. However, its significance and mechanism of development remains unclear. Human defensin 5 is a specific marker of Paneth cells and has been shown to represent one of the target genes of the Apc/beta-catenin/Tcf pathway. The aim of this study was to evaluate the frequency of Paneth cell differentiation in a variety of colonic neoplasms, and to investigate the role of human defensin 5 and beta-catenin in this process. The clinical and pathologic findings, including histologic evidence of Paneth cell differentiation and immunostaining for human defensin 5 and beta-catenin, were evaluated in 29 samples of nonneoplastic colonic mucosa, 18 hyperplastic polyps, 10 sessile serrated adenomas, 12 traditional serrated adenomas, 21 mixed polyps, 39 conventional adenomas, and 40 adenocarcinomas. Human defensin-5 and beta-catenin expression were evaluated for the location and degree of staining in all cell types (dysplastic and nondysplastic) and correlated with histologic areas of Paneth cell differentiation in all types of polyps. Histologic evidence of Paneth cell differentiation was observed in 15 conventional adenomas (38.5%) and 1 adenocarcinoma (2.5%) but not in other types of polyps. Human defensin-5 immunostaining was positive in the cytoplasm of all nonneoplastic Paneth cells and all neoplastic cells with Paneth cell differentiation. Human defensin-5 expression was noted in 0% of hyperplastic polyps, 10% of sessile serrated adenomas, 25% of traditional serrated adenomas, 33.3% of mixed polyps, 82.1% of conventional adenomas, and 17.5% of adenocarcinomas: human defensin 5 expression was significantly higher in conventional adenomas compared to all other groups (P < .01). Seventeen (53.1%) of 32 human defensin 5 positive conventional adenomas, 6 (86%) of 7 of human defensin 5 positive adenocarcinomas, and all human defensin 5-positive sessile serrated adenomas, traditional serrated adenomas, and mixed polyps did not show histologic evidence of Paneth cell differentiation. All mixed polyps (100%) that revealed human defensin 5 expression (7; 33.3%) revealed conventional dysplasia. In the positive mixed polyp cases, human defensin 5 was only positive in areas of conventional dysplasia. Of the 31 conventional adenomas with nuclear beta-catenin staining, 15 (48.4%) revealed histologic evidence of Paneth cell differentiation, and all of the neoplastic cells with Paneth cell differentiation showed nuclear beta-catenin staining, whereas nonneoplastic Paneth cells consistently showed a normal pattern of membranous beta-catenin staining. A strong topographical correlation was noted between human defensin 5 expression and nuclear beta-catenin expression in conventional adenomas and in conventional dysplastic epithelium of mixed polyps. Paneth cell differentiation is common in early colonic neoplasms that develop via the conventional adenoma-carcinoma carcinogenic pathway. Activation of Apc/beta-catenin/Tcf pathway may play a role in Paneth cell differentiation in human colonic neoplasms.

Germinal-center T-helper-cell markers PD-1 and CXCL13 are both expressed by neoplastic cells in angioimmunoblastic T-cell lymphoma.

Gene expression profiling identified genes uniquely expressed by human germinal-center T-helper (GCTh) cells, including programmed death-1 (PD-1) and CXCL13. Recently, we demonstrated that PD-1 is an immunophenotypic marker of GCTh cells and angioimmunoblastic T-cell lymphoma (AITL). The goal of this study was to investigate the expression pattern of CXCL13 in comparison with PD-1. We studied 63 cases of T-cell lymphoproliferative disorders, including 22 cases of AITL. In cases of AITL, PD-1+ and CXCL13+ neoplastic cells were seen at foci of expanded CD21+ follicular dendritic cell networks. CXCL13 expression was limited in other peripheral T-cell lymphomas. PD-1 and CXCL13 identified germinal-center T-helper cells, showed a similar pattern of expression in AITL, and should serve as useful new markers for AITL. The similar pattern of expression of CXCL13 and PD-1 in AITL provides further evidence that AITL is a neoplasm derived from germinal-center T-helper cells.

Vascular and lymphatic properties of the superficial and deep lamina propria in Barrett esophagus.

A well-known type of mesenchymal/epithelial interaction occurs in Barrett esophagus (BE) characterized by the formation of a new, superficially located, muscularis mucosae (MM), which results in the division of the lamina propria (LP) into a superficial and deep compartment. The vascular and lymphatic properties of these 2 regions of LP are unknown. The risk of metastases of carcinomas that infiltrate these 2 anatomic areas also remains unclear. The aim of this study was to evaluate the density of blood vessels and lymphatic spaces within the superficial and deep LP and submucosa in patients with BE, and to compare the results to normal squamous-lined esophagus. Thirty esophago-gastrectomy specimens were stained immunohistochemically with CD31 (stains blood vessel and lymphatic endothelium) and D2-40 (stains lymphatic endothelium only). The density of CD31+ blood and lymphatic vessels (per 20 x field) in BE (superficial LP=37 and deep LP=38) was significantly lower compared with the LP of squamous-lined esophagus (68; P<0.001). However, the total number of blood and lymphatic vessels in the superficial and deep LP in BE was statistically similar to the LP of squamous-lined esophagus. The density of CD31+ blood and lymphatic vessels (per 20x field) in the submucosa of BE (21) was not significantly different from the submucosa of squamous-lined esophagus (23; P>0.05). We conclude that in BE, the "native" LP in squamous-lined esophagus is separated into 2 LP compartments (superficial and deep) by the formation of a new MM. These findings suggest that carcinomas that invade through the superficial MM into the deep LP should be considered "intramucosal" rather than "submucosal." Further outcome studies are needed to evaluate the risk of vascular/lymphatic metastasis in BE patients with different levels of LP invasion.

Characteristic expression patterns of TCL1, CD38, and CD44 identify aggressive lymphomas harboring a MYC translocation.

The distinction between Burkitt (BL) or atypical Burkitt/Burkitt-like lymphomas harboring a MYC translocation (MYC+) and diffuse large B-cell lymphomas (DLBCLs) with high proliferation fractions but without a MYC translocation (MYC-) can be difficult using standard morphologic and immunohistochemical criteria. Recently, unique gene expression profiles differentiating BL and DLBCL were reported and include higher transcript levels of T-cell leukemia-1 (TCL1) and CD38 and lower transcript levels of CD44 in MYC+ BL relative to MYC- DLBCL. We examined a cohort of 67 cytogenetically defined aggressive lymphomas using immunohistochemical techniques for expression of TCL1, CD38, and CD44 and found distinct expression patterns between MYC+ and MYC- tumors. Furthermore, these markers are better predictors of MYC status than combined staining for CD10 and BCL2. Thus staining for TCL1, CD38, and CD44 are useful ancillary tests to identify B-cell tumors for which confirmatory cytogenetic and/or fluorescent in situ hybridization studies assessing the status of the MYC locus should be pursued.

Ontogeny of the eotaxins in human lung.

The ontogeny of the C-C chemokines eotaxin-1, eotaxin-2, and eotaxin-3 has not been fully elucidated in human lung. We explored a possible role for eotaxin in developing lung by determining the ontogeny of eotaxin-1 (CCL11), eotaxin-2 (CCL24), eotaxin-3 (CCL26), and the eotaxin receptor, CCR3. We tested discarded surgical samples of developing human lung tissue using quantitative RT-PCR (QRT-PCR) and immunostaining for expression of CCL11, CCL24, CCL26, and CCR3. We assessed possible functionality of the eotaxin-CCR3 system by treating lung explant cultures with exogenous CCL11 and analyzing the cultures for evidence of changes in proliferation and activation of ERK1/2, a signaling pathway associated with CCR3. QRT-PCR analyses of 22 developing lung tissue samples with gestational ages 10-23 wk demonstrated that eotaxin-1 mRNA is most abundant in developing lung, whereas mRNAs for eotaxin-2 and eotaxin-3 are minimally detectable. CCL11 mRNA levels correlated with gestational age (P < 0.05), and immunoreactivity was localized predominantly to airway epithelial cells. QRT-PCR analysis detected CCR3 expression in 16 of 19 developing lung samples. Supporting functional capacity in the immature lung, CCL11 treatment of lung explant cultures resulted in significantly increased (P < 0.05) cell proliferation and activation of the ERK signaling pathway, which is downstream from CCR3, suggesting that proliferation was due to activation of CCR3 receptors by CCL11. We conclude that developing lung expresses the eotaxins and functional CCR3 receptor. CCL11 may promote airway epithelial proliferation in the developing lung.

Programmed death-1 (PD-1) is a marker of germinal center-associated T cells and angioimmunoblastic T-cell lymphoma.

Programmed death-1 (PD-1), a member of the CD28 costimulatory receptor family, is expressed by germinal center-associated T cells in reactive lymphoid tissue. In a study of a wide range of lymphoproliferative disorders, neoplastic T cells in 23 cases of angioimmunoblastic lymphoma were immunoreactive for PD-1, but other subtypes of T cell and B cell non-Hodgkin lymphoma, as well as classic Hodgkin lymphoma, did not express PD-1. The pattern of PD-1 immunostaining of neoplastic cells in angioimmunoblastic lymphoma was similar to that reported for CD10, a recently described marker of neoplastic T cells in angioimmunoblastic lymphoma. Tumor-associated follicular dendritic cells in cases of angioimmunoblastic lymphoma were found to express PD-L1, the PD-1 ligand. In addition, PD-1-positive reactive T cells formed rosettes around neoplastic L&H cells in 14 cases of nodular lymphocyte predominant Hodgkin lymphoma studied. These findings, along with data from previous studies, suggest that angioimmunoblastic lymphoma is a neoplasm of germinal center-associated T cells and that there is an association of germinal center-associated T cells and neoplastic cells in nodular lymphocyte predominant Hodgkin lymphoma. PD-1 is a useful new marker for angioimmunoblastic lymphoma and lends further support to a model of T-cell lymphomagenesis in which specific subtypes of T cells may undergo neoplastic transformation and result in specific, distinct histologic, immunophenotypic, and clinical subtypes of T-cell neoplasia.

T-bet, a T cell-associated transcription factor, is expressed in Hodgkin's lymphoma.

T-bet, a T-box transcription factor, is expressed in CD4+ T lymphocytes committed to Th1 T-cell development and may participate in immunoglobulin class switching in B lymphocytes. T-bet is also expressed in a subset of T-cell lymphomas, particularly those that express other markers of Th1 T cell differentiation, and in a subset of B-cell non-Hodgkin's lymphomas. Because of the evidence that Hodgkin's lymphoma is a neoplasm of B cells, we examined cases of Hodgkin's lymphoma for T-bet expression by immunohistochemical staining and found that neoplastic cells in most cases of classic Hodgkin's lymphoma (33 of 37 cases, 89%), including nodular sclerosis type (17 of 21 cases, 81%) and mixed cellularity type (15 of 15, 100%), express T-bet. Neoplastic cells in most cases of nodular lymphocyte-predominant Hodgkin's lymphoma (15 of 18, 83%), a distinct clinical entity that differs from classic Hodgkin's lymphoma, also express T-bet. A Hodgkin's lymphoma-derived cell line, L1236, expresses T-bet by Western blot analysis as well as by immunohistochemical staining. In contrast, almost all cases of diffuse large B-cell lymphoma and most cases of anaplastic large cell lymphoma, neoplasms that may be confused with Hodgkin's lymphoma, are negative for T-bet. On that basis, T-bet should serve as a useful new marker for the diagnosis of Hodgkin's lymphoma. In addition, because T-bet expression is not detectable in the majority of reactive B cells, including germinal-center B cells, but is characteristically expressed by the neoplastic cells in Hodgkin's lymphoma, thought to be derived from germinal-center B cells, T-bet may play a role in Hodgkin's lymphoma oncogenesis.

The CD45 isoform B220 identifies select subsets of human B cells and B-cell lymphoproliferative disorders.

The B220 isoform of CD45, a pan B-cell marker in mice, is expressed by only a subset of human B cells that do not express the memory B-cell marker CD27, suggesting that it is a differentiation-specific isoform of CD45. We examined normal human peripheral blood B cells, secondary lymphoid tissue, and a range of human B-cell lymphoproliferative disorders for the expression of B220 by flow cytometric immunophenotyping and immunohistochemical staining. We found that a subset of human B cells in peripheral blood is positive for B220 by flow cytometric immunophenotypic analysis. In reactive lymphoid tissues, B220 is expressed by B cells occupying the mantle zones and by a subpopulation of germinal center cells, but, in contrast, marginal zone B cells in the spleen do not express B220. Of 94 cases of B-cell lymphoproliferative disorders, 33 (35%) were positive for B220 by flow cytometric immunophenotypic analysis, including most cases of marginal zone lymphoma, follicular lymphoma, and lymphoplasmacytic lymphoma. In contrast, all cases of precursor B lymphoblastic leukemia/lymphoma, mantle cell lymphoma, and chronic lymphocytic leukemia/small lymphocytic lymphoma were negative for B220. Immunohistochemical staining for B220 correlated with flow cytometric analysis for all cases studied by both methods. Our data demonstrate that B220 is expressed in a select subset of normal, reactive B cells in a pattern that is consistent with a marker of naive B cells. However, this restricted expression pattern is not seen in B-cell lymphoproliferative disorders. Discordance between the B220 expression patterns of normal mantle and marginal zone B cells and their respective neoplastic counterparts may aid in the distinction between normal and neoplastic proliferations at these anatomical sites.

T-bet, a T-cell-associated transcription factor, is expressed in a subset of B-cell lymphoproliferative disorders.

T-bet, a T-box transcription factor, is expressed in CD4+ T lymphocytes committed to Th1 T-cell development and in a subset of T-cell non-Hodgkin lymphomas. Recent evidence indicates that T-bet also is expressed in B lymphocytes and might participate in immunoglobulin class switching. We examined T-bet expression in 116 cases of B-cell lymphoproliferative disorders by immunostaining and found that T-bet was expressed consistently in precursor B-cell lymphoblastic leukemia/lymphoblastic lymphoma (14/14 cases) in contrast with precursor T-cell lymphoblastic leukemia/lymphoblastic lymphoma, which is consistently T-bet- (13 cases), as previously reported. T-bet is expressed in memory B cell-derived neoplasms (chronic lymphocytic leukemia, marginal zone lymphoma, hairy cell leukemia; 35/42 cases) but not in cases of mantle cell, follicular, and large cell lymphoma (43 cases). Expression of T-bet in precursor B-cell lymphoblastic leukemia/lymphoblastic lymphoma was confirmed by Western blot analysis. The expression of T-bet in a significant subset of B-cell lymphoproliferative disorders but not in the vast majority of reactive B cells suggests it might have a role in the oncogenesis of T-bet+ B-cell neoplasms. In addition, T-bet should serve as a useful new marker for the diagnosis and subtyping of B-cell lymphoproliferative disorders.

Differential expression of T-bet, a T-box transcription factor required for Th1 T-cell development, in peripheral T-cell lymphomas.

We studied T-bet expression in 91 cases of peripheral T-cell lymphoma (PTCL) by immunostaining and found expression in 42 cases (46%), including all 5 lymphoepithelioid lymphoma cases and 12 (86%) of 14 angioimmunoblastic lymphoma cases, but only 9 (25%) of 36 anaplastic large cell lymphoma cases. Expression of T-bet in PTCL correlates with expression of other markers of Th1 T-cell differentiation, including CXCR3 (P < .0001), CD69 (P = .0013), LEF-1 (P = .0007), and OX40/CD134 (P = .005), and absence of expression of markers of Th2 T-cell differentiation, including CD30 (P = .0001) and CXCR4 (P = .0144). Of 22 cases of PTCL immunoreactive for all Th1-associated markers previously studied and nonreactive for Th2-associated markers, 20 (91%) were immunoreactive for T-bet. Of 22 PTCL cases immunoreactive for Th2-associated markers studied and nonreactive for all Th1-associated markers studied, 4 (18%) were immunoreactive for T-bet. The remaining 47 PTCL cases (52%) exhibited incomplete or mixed staining for Th1- and Th2-associated markers, with 18 (38%) of 47 immunoreactive for T-bet. T-bet is a new marker that may contribute to the diagnosis and subtyping of PTCLs. T-bet expression in these neoplasms provides further support for a model of PTCL in which tumor subsets express markers of, and may be derived from, Th1- or Th2-committed T cells.

Mucin core peptide expression can help differentiate Barrett's esophagus from intestinal metaplasia of the stomach.

It is important to distinguish Barrett's esophagus (BE) from intestinal metaplasia related to carditis because these conditions have a different natural history, risk of malignancy, and treatment. However, the distinction between these entities is difficult both clinically and pathologically. The aim of this study was to evaluate and compare the immunostaining pattern of five mucin core polypeptides in BE to cases of carditis or antritis with intestinal metaplasia. Routinely processed mucosal biopsies from 22 patients with intestinal-type BE, 24 patients with cardia intestinal metaplasia (10 Helicobacter pylori positive), 17 patients with antral intestinal metaplasia (all H. pylori positive), 20 control patients with a normal antrum, and 22 control patients with a normal cardia were immunostained with monoclonal antibodies against MUC1, MUC2, MUC3, MUC5AC, and MUC6 mucin core polypeptides. Staining was evaluated separately for goblet cells and non-goblet columnar cells and compared between all groups. A significantly higher number of BE cases (P < 0.05) showed goblet cell staining for MUC1 (55%) or MUC6 (32%) compared with patients with carditis with intestinal metaplasia (MUC1 14%, MUC6 7%) or antritis with intestinal metaplasia (MUC1 6%, MUC6 0%). BE also showed a higher frequency of MUC1 and MUC6 positivity in non-goblet columnar cells compared with carditis and antritis cases with intestinal metaplasia. Only cases of BE showed combined MUC1 and MUC6 staining (sensitivity 23%, specificity 100%). The sensitivity and specificity of MUC1 staining for BE are 55% and 96%, respectively, and for MUC6 staining 30% and 96%, respectively. Interestingly, normal gastric cardia mucosa also showed a significantly higher prevalence of MUC2 and MUC3 expression in glandular epithelium (29% and 38%, respectively) compared with the antrum (0% for both markers) (P < 0.05). In conclusion, MUC1 and MUC6 expression in BE is distinct from that of the cardia and antrum with intestinal metaplasia; thus, immunophenotyping for these markers may have some value in a subset of patients in helping to separate BE from patients with intestinal metaplasia of the cardia. Columnar epithelium in the "normal" gastric cardia has a partially intestinalized phenotype and, as a result, may represent an early form of metaplastic epithelium.