Mediastinal (thymic) large B-cell lymphoma: where do we stand?

Mediastinal (thymic) B-cell lymphoma (MBL) is a locally highly aggressive tumour that was first definitively described in the early 1980s. The incidence of MBL is low, which made disease characterisation difficult initially. However, MBL has several peculiar clinical, morphological, immunological, and genetic features. Collectively, these characteristics distinguish it from other diffuse, large B-cell lymphomas. Consequently, MBL has become a defined subtype of diffuse large B-cell lymphoma with its own code (9679/3) in the International Classification of Diseases. New insights into the biological and clinical aspects of MBL have been gained from the study of large numbers of cases. Nevertheless, the histogenesis of the disease is not yet fully understood. We review the available data on MBL with special emphasis on its morphological, immunological, and genetic properties. Also discussed are recent data on molecular genetics, biology, and treatment.

Mediastinal B-cell lymphoma, a lymphoma type with several characteristics unique among diffuse large B-cell lymphomas

Mediastinal B-cell lymphoma is a locally highly aggressive tumor with a rather unique pattern of clinical, morphologic, imunologic, and genetic features distinct from other diffuse large B-cell lymphomas. Characterization of this disease has been hampered by the relatively low incidence of this lymphoma type. Although recent studies on larger numbers of cases have allowed new insights into biology and clinics of this lymphoma type, the histogenesis of mediastinal B-cell lymphoma is not yet fully understood. This review will list morphologic, immunlogic, and genetic properties of mediastinal B-cell lymphoma and discuss recent data regarding the biology of this lymphoma type.

Low incidence of SV40-like sequences in ependymal tumours

Between 1955 and 1963, millions of children and adults were exposed to SV40-contaminated poliovirus vaccines. The oncogenic potential of this polyomavirus was revealed when intracerebral inoculation of SV40 into newborn hamsters resulted in the development of ependymomas and choroid plexus papillomas. Subsequently, SV40-like sequences were repeatedly detected in human ependymomas with broadly ranging incidence rates of 7-90%. Most epidemiological studies, however, have not described an increased occurrence of ependymomas. To gain more data on this controversial issue, this study examined 62 archived ependymal tumours from 31 children and 31 adults who underwent surgery between 1990 and 1999. Only three (5%) of the tumours--including 24 classical, 20 anaplastic, and 12 myxopapillary ependymomas; one subependymoma; and five ependymoblastomas--revealed subgenomic SV40 sequences. None of the ependymomas in patients born between 1920 and 1960 demonstrated SV40-like sequences. The positive tumours represent 7% of grade II and III ependymomas (two paediatric and one adult tumour). DNA sequencing of the PCR product revealed identical sequences of SV40 in the positive ependymal tumours. Compared with the results from other countries, this incidence rate is relatively low. Therefore, it seems likely that significant differences between individual countries exist regarding the prevalence of SV40-positive ependymomas. These differences may reflect different degrees of exposure to SV40-contaminated polio vaccine.

Isotype-switched immunoglobulin genes with a high load of somatic hypermutation and lack of ongoing mutational activity are prevalent in mediastinal B-cell lymphoma

Primary mediastinal B-cell lymphoma (PMBL) is a subentity of diffuse large B-cell lymphoma with characteristic clinical, histomorphologic, immunophenotypical, and genetic features. Unlike other B-cell lymphomas, PMBL has not yet been the subject of comprehensive molecular studies on the rearranged immunoglobulin (Ig) gene. Such investigations have proved essential to obtaining information about the differentiation stage of the lymphomagenic B cell. In the present study, the clonally rearranged immunoglobulin heavy-chain gene of 13 PMBL cases is analyzed by polymerase chain reaction (PCR) in conjunction with cloning and DNA sequencing. Twelve of 13 rearrangements were potentially functional. All clonally rearranged immunoglobulin genes bore a high load of somatic mutations (average, 13.0%), which appeared to be selected for a functional antibody in the majority of cases. The comparison of cloned PCR products revealed no evidence of ongoing mutation of the immunoglobulin variable gene. By means of reverse-transcriptase PCR, lymphoma-specific immunoglobulin transcripts were detected in 8 of 13 cases, all of which were of the postswitched type, whereas immunoglobulin protein expression was undetectable except for 1 case. A PMBL cell line, MedB-1, generated from an IgG(-) parental tumor, constitutively expressed IgG protein in a subset of cells, which was moderately suppressed by interleukin-4 and up-regulated in the presence of dexamethasone. PMBL is thus characterized by a heavily mutated, class-switched immunoglobulin gene without evidence of ongoing mutational activity. Moreover, our data indirectly suggest that regulation by extrinsic signals contributes to the immunoglobulin-negative phenotype of PMBL.

Clustering of colonic lamina propria CD4(+) T cells to subepithelial dendritic cell aggregates precedes the development of colitis in a murine adoptive transfer model

Initial lesions in inflammatory bowel disease induced during the repopulation of immunodeficient RAG1(-/-) mice with immunocompetent CD4(+) T cells have not been previously described. In this transfer colitis model, we followed CD4(+) T cell repopulation in the host by injecting autofluorescent CD4(+) T cells from congenic, enhanced green fluorescent protein (eGFP)-transgenic mice. This allowed the direct, sensitive, and unambiguous histological detection of the repopulation of the intestinal tract, mesenteric lymph nodes, and spleen of the host with donor eGFP(+) CD4(+) T cells. We identified in RAG1(-/-) mice intestinal dendritic cell (DC) aggregates under the basal crypt epithelium at the mucosa/submucosa junction from which F4/80(+) macrophages were excluded. At Days 8 to 11 posttransfer (before colitis was manifest), CD4(+) T cells clustered and proliferated in CD11c(+) DC aggregates. T cell clustering was most pronounced in the cecum where histologically overt colitis became manifest 5 to 10 days later. Junctional DC aggregates were thus prevalent in the triggering phase of the disease. The data suggest that pathogenic T cell responses inducing inflammatory bowel disease are primed or restimulated in situ in junctional CD4(+) T cell/DC aggregates.

Activating immunity in the liver. I. Liver dendritic cells (but not hepatocytes) are potent activators of IFN-gamma release by liver NKT cells

A prominent subset of the hepatic innate immune system is alpha-galactosylceramide (alphaGalCer)-reactive, (CD4(+) and CD4(-)CD8(-)) CD1d-restricted NKT cells. We investigated in C57BL/6 (B6) mice which hepatic cell type stimulates hepatic NKT cell activation. Surface expression of CD1d but not CD40, CD80, or CD86 costimulator molecules was detected in hepatocytes. Pulsed in vitro or in vivo with alphaGalCer, hepatocytes triggered IL-4 release by liver NKT cells but required exogenous IL-12 to trigger IFN-gamma release by NKT cells. Liver dendritic cells (DC) isolated from nontreated mice showed low surface expression of MHC, CD1d, and CD40, CD80, or CD86 costimulator molecules that were strikingly up-regulated after alphaGalCer injection. Although liver CD11c(+) DC displayed lower CD1d surface expression than hepatocytes, they were potent stimulators of IFN-gamma and IL-4 release by liver NKT when pulsed with alphaGalCer in vitro or in vivo. Liver DC are thus potent stimulators of proinflammatory cytokine release by NKT cells, are activated themselves in the process of NKT cell activation, and express an activated phenotype after the NKT cell population is eliminated following alphaGalCer stimulation.

Molecular-cytogenetic comparison of mucosa-associated marginal zone B-cell lymphoma and large B-cell lymphoma arising in the gastro-intestinal tract

Extranodal B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type may represent a model of lymphoma progression, because a small cell component frequently occurs in the large cell variants. We studied 52 extranodal B-cell lymphomas: 18 extranodal marginal zone B-cell lymphomas of MALT type (MZBL,MT), 7 MZBL,MT of the gastro-intestinal tract with a diffuse large B-cell component (giMZBLplusLBCL), and 27 diffuse large B-cell lymphomas of the gastro-intestinal tract without small cell component (giLBCL). Analytical techniques were comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The translocation t(11;18) was found as the sole aberration in two MZBL,MT only. In contrast to this, t(11;18)-negative MZBL,MT were characterized by frequent gains on chromosome 3 and DNA amplifications on 2p13-p15. Furthermore, we found a clonal lymphoma progression from the small to the large cell component with accumulation of gains and losses of chromosomal material in the large cell component in giMZBLplusLBCL. Aberrations overlapping with MZBL,MT and giMZBLplusLBCL included losses on chromosome 13, amplifications of the REL proto-oncogene, or gains on chromosome 12. In addition, the large cell component revealed gains on 8q24, including amplifications of the MYC proto-oncogene, and losses on 2q. The giLBCL had frequent gains on chromosomes 12 and 9, as well as on 11q, and losses on 6q. We conclude that, based on the distinctive and partly overlapping patterns of genetic aberrations, MALT lymphomas can be divided into different genetic subgroups.

In situ characterization of genetically targeted (green fluorescent) single cells and their microenvironment in an adoptive host

Stable expression of transgene-encoded enhanced green fluorescence protein (eGFP) was used as a sensitive and specific marker to detect in situ donor cells engrafted into different tissues of adoptive hosts. eGFP(+) lymphoid or myeloid cells (eg, CD4(+) T cells or bone marrow-derived dendritic cells) from eGFP-transgenic C57BL/6 donor mice were injected into congenic, immunodeficient RAG1(-/-) C57/BL6 hosts. eGFP(+) cells were detected in the adoptive host from 2 days to 4 weeks after transfer using an optimized method of fixed cryopreservation to process the tissue. This allowed the simple, sensitive, and specific detection of eGFP(+) donor cells in histological sections of transplanted hosts. We further demonstrate that this technique can be combined with other established labeling methods such as 1) immunofluorescent labeling to characterize the host cells interacting with engrafted cells and to determine the phenotype of the engrafted cells in situ; 2) terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining to detect apoptotic death of engrafted and autochthonous cell populations; and 3) fluorescent antibody labeling of incorporated bromodeoxyuridine to measure the fraction of proliferating cells in the graft.

MedB-1, a human tumor cell line derived from a primary mediastinal large B-cell lymphoma

Primary mediastinal B-cell lymphoma is a locally highly aggressive but poorly disseminating tumor composed of medium sized or large cells most probably of thymic medullary origin. It has a mature B-cell phenotype, typically lacks immunoglobulin expression and has variable defects in expression of HLA-molecules. We present here a cell line, MedB-1, derived from such a tumor. As is frequently found in mediastinal B-cell lymphomas in situ, MedB-1 is CD10(-), CD19(+), CD21(-), CD22(+), CD23(+), CD25(-), CD37(+), CD38(-), CD39(+), CD40(+), CD54(+), CD95(+). Like the parental tumor, MedB-1 lacks HLA-A,B,C alpha-chains and beta(2)microglobulin and expresses HLA-D molecules at decreased levels. Both parental tumor and MedB-1 cells are clonally related as shown by immunoglobulin heavy chain gene rearrangement analysis. Unlike the parental tumor tissue, the MedB-1 cell line cytoplasmically expresses IgG/kappa in a very small subset of cells under standard culture conditions. MedB-1 does not contain any Epstein-Barr virus DNA. In a tissue adhesion assay MedB-1 cells showed an extensive binding to the medullary region of normal thymus. Altogether, MedB-1 is a suitable tool for functional and molecular analysis of this distinct lymphoma entity.

MHC-II-independent CD4+ T cells induce colitis in immunodeficient RAG-/- hosts

CD4(+) alpha beta T cells from either normal C57BL/6 (B6) or MHC-II-deficient (A alpha(-/-) or A beta(-/-)) B6 donor mice engrafted into congenic immunodeficient RAG1(-/-) B6 hosts induced an aggressive inflammatory bowel disease (IBD). Furthermore, CD4(+) T cells from CD1d(-/-) knockout (KO) B6 donor mice but not those from MHC-I(-/-) (homozygous transgenic mice deficient for beta(2)-microglobulin) KO B6 mice induced a colitis in RAG(-/-) hosts. Abundant numbers of in vivo activated (CD69(high)CD44(high)CD28(high)) NK1(+) and NK1(-) CD4(+) T cells were isolated from the inflamed colonic lamina propria (cLP) of transplanted mice with IBD that produced large amounts of TNF-alpha and IFN-gamma but low amounts of IL-4 and IL-10. IBD-associated cLP Th1 CD4(+) T cell populations were polyclonal and MHC-II-restricted when derived from normal B6 donor mice, but oligoclonal and apparently MHC-I-restricted when derived from MHC-II-deficient (A alpha(-/-) or A beta(-/-)) B6 donor mice. cLP CD4(+) T cell populations from homozygous transgenic mice deficient for beta(2)-microglobulin KO B6 donor mice engrafted into RAG(-/-) hosts were Th2 and MHC-II restricted. These data indicate that MHC-II-dependent as well as MHC-II-independent CD4(+) T cells can induce a severe and lethal IBD in congenic, immunodeficient hosts, but that the former need the latter to express its IBD-inducing potential.

CD95 ligand (CD95L) immunohistochemistry: a critical study on 12 antibodies

In recent years, some studies on the expression of CD95(Fas/APO-1) ligand (CD95L) in tissues or cells raised concerns about the specificity of the antibodies used. We therefore tested 12 CD95L antibodies for their reliability in immunocyto/histochemistry by (i) staining CD95L-transfected and control CV-1/EBNA cells and (ii) comparing staining patterns in immunohistochemically labeled tissue sections with the localization of CD95L+ cells in in situ hybridization. While G247-4, NOK-1, NOK-2, 4H9, and MIKE-1 stained CD95L-transfected cells and did not significantly bind to controls, G247-4 was the only antibody giving satisfying signals in tissue sections perfectly matching the distribution of CD95L+ cells by in situ hybridization. MAb 33, C-20, and N-20 comparably stained both transfected and control cells and showed considerable background or falsely positive staining in sections. MIKE-2, 8B8, A11, and 4A5 did not or only very faintly bind to either cells and, thus, were not tested on sections. We conclude that G247-4 is the only tested antibody that is recommendable for immunohistochemistry.

Primary gastric apoptosis-rich T-cell lymphoma co-expressing CD4, CD8, and cytotoxic molecules

In contrast to primary gastric lymphomas of B-cell type, little is known about primary gastric T-cell lymphomas. We describe three cases with remarkably similar features: diffuse growth, epitheliotropism, medium too large cell size, high apoptotic rates, and a CD3+, CD4+, CD8+, CD45RO+ immunophenotype. Clonal TCRgamma gene rearrangement was shown in two cases. Epstein-Barr virus infection was excluded in two cases. Taking advantage of fresh-frozen material, we analyzed two cases further, revealing CD5-, CD16+, CD56-, CD57-, CD25+, CD30+, CD103 (alphaEbeta7)+, bcl-2 protein+, CD95+, CD95 ligand(L)-. CD95L, however, was detected in histiocytic and fibroblastoid by stander cells. The lymphomas expressed granzyme B, perforin, and the TIA-1 antigen in various combinations. All three cases had a very unfavorable clinical course characterized by local recurrence and/or dissemination to other epithelial sites, leading to death within 6-12 months after the initial diagnosis despite surgery and aggressive antineoplastic treatment. These data suggest a novel variant of peripheral T-cell lymphoma operationally characterized as primary gastric, apoptosis-rich, CD103+, EBV-, T-cell lymphoma co-expressing CD4, CD8, CD16 and cytotoxic molecules.

Epstein-Barr virus meningoencephalitis with a lymphoma-like response in an immunocompetent host

We report the clinical and neuropathological findings in an immunocompetent 19-year-old patient with a fatal acute Epstein-Barr virus (EBV) meningoencephalitis and a lymphoma-like B-lymphocyte response. Our results suggest that an immunotoxic rather than direct viral neuronal invasion mediates brain damage in EBV encephalitis and rule out primary central nervous system lymphoma (PCNSL) in our patient. We discuss immunosuppression as a therapeutic option, because present strategies mainly consist of symptomatic therapy due to unclear pathogenesis and nonavailability of effective antiviral agents.

Colitis-inducing potency of CD4+ T cells in immunodeficient, adoptive hosts depends on their state of activation, IL-12 responsiveness, and CD45RB surface phenotype

We studied the induction, severity and rate of progression of inflammatory bowel disease (IBD) induced in SCID mice by the adoptive transfer of low numbers of the following purified BALB/c CD4+ T cell subsets: 1) unfractionated, peripheral, small (resting), or large (activated) CD4+ T cells; 2) fractionated, peripheral, small, or large, CD45RBhigh or CD45RBlow CD4+ T cells; and 3) peripheral IL-12-unresponsive CD4+ T cells from STAT-4-deficient mice. The adoptive transfer into SCID host of comparable numbers of CD4+ T cells was used to assess the colitis-inducing potency of these subsets. Small CD45RBhigh CD4+ T lymphocytes and activated CD4+ T blasts induced early (6-12 wk posttransfer) and severe disease, while small resting and unfractionated CD4+ T cells or CD45RBlow T lymphocytes induced a late-onset disease 12-16 wk posttransfer. SCID mice transplanted with STAT-4-/- CD4+ T cells showed a late-onset IBD manifest > 20 wk posttransfer. In SCID mice with IBD transplanted with IL-12-responsive CD4+ T cells, the colonic lamina propria CD4+ T cells showed a mucosa-seeking memory/effector CD45RBlow Th1 phenotype abundantly producing IFN-gamma and TNF-alpha. In SCID mice transplanted with IL-12-unresponsive STAT-4-/- CD4+ T cells, the colonic lamina propria, mesenteric lymph node, and splenic CD4+ T cells produced very little IFN-gamma but abundant levels of TNF-alpha. The histopathologic appearance of colitis in all transplanted SCID mice was similar. These data indicate that CD45RBhigh and CD45RBlow, IL-12-responsive and IL-12-unresponsive CD4+ T lymphocytes and lymphoblasts have IBD-inducing potential though of varying potency.

CD95 ligand (CD95L) in normal human lymphoid tissues: a subset of plasma cells are prominent producers of CD95L

CD95(Fas/APO-1)-ligand (CD95L) mediates apoptosis by trimerization of the CD95 receptor on the surface of sensitive cells. In vitro studies have shown CD95L expression mainly by activated T cells and suggested a role for CD95L in the regulation of immune responses. Little is known, however, about the cellular distribution of CD95L in situ in the normal human immune system. We investigated CD95L expression in tissue sections of the thymus, lymph node, spleen, tonsil, and gastrointestinal tract using in situ hybridization and two monoclonal antibodies. In all these organs, cells expressing CD95L message and protein were scarce and comprised scattered lymphocytes, rare nonlymphoid cells, and a subset of epithelioid endothelial cells. Surprisingly, a subset of plasma cells turned out to be the most prominent producers of CD95L, matching the reports on CD95L in myeloma cells. CD95L+ plasma cells were most numerous in the mucosa-associated lymphoid tissue. This also applied to acquired mucosa-associated lymphoid tissue in chronic gastritis in which CD95L+ plasma cells were found scattered in the lamina propria. Our data suggest that plasma cells as yet may be neglected modulators of immune responses.

T cell-mediated, IFN-gamma-facilitated rejection of murine B16 melanomas

The murine melanoma cell line B16.F10 (H-2b) was used to study specific T cell responses that reject tumors. Stable B16 transfectants were established that express viral Ags, either the hepatitis B surface Ag (HBsAg) or the large tumor Ag (T-Ag) of SV40. B16 cells and their transfected sublines were CD40+ CD44+ but expressed no (or low levels of the) costimulator molecules CD154 (CD40L), CD48, CD54, CD80, and CD86. Surface expression of MHC class I (Kb, Db) and class II (I-Ab) molecules by B16 cells was low, but strikingly up-regulated by IFN-gamma. CD95 (Fas) and CD95 ligand (CD95L (FasL)) were "spontaneously" expressed by B16 cells growing in vitro in serum-free medium; these markers were strikingly up-regulated by IFN-gamma. B16 cells coexpressing CD95 and CD95L were irreversibly programmed for apoptosis. In vitro, noninduced B16 transfectants stimulated a specific IFN-gamma release response, but no cytolytic response (in a 4-h assay) in MHC class I-restricted CTL; in contrast, IFN-gamma-induced B16 targets were efficiently and specifically lysed by CTL. In vivo, B16 transfectants were specifically rejected by DNA-vaccinated syngeneic hosts through a T-dependent immune effector mechanism. The tumors showed evidence of massive apoptosis in vivo during the rejection process. The data suggest that CTL-derived IFN-gamma enhances an intrinsic suicide mechanism of these tumor cells in addition to facilitating lytic interactions of effectors with tumor targets.

A pancolitis resembling human ulcerative colitis (UC) is induced by CD4+ TCR alphabeta T cells of athymic origin in histocompatible severe combined immunodeficient (SCID) mice

CD4+ TCRalphabeta+ T cells from the colonic lamina propria of athymic (nude) mice were adoptively transferred into histocompatible (SCID) mice homozygous for the autosomal recessive mutation scid (severe combined immunodeficiency). Transfer of these extrathymic CD4+ T cells into SCID mice induced a pancolitis in the adoptive host. The histopathology of this inflammatory response was restricted to the colon and closely resembled human UC. CD4+ T cells infiltrating the colonic lamina propria of diseased SCID mice displayed the surface phenotype of mucosa-seeking memory/effector cells, expressed interferon-gamma (IFN-gamma), and lysed targets in a Fas (CD95)/FasL-dependent pathway. Massive accumulation of oligoclonal CD4+ T cells of athymic origin with the phenotype of Th1 memory/effector T cells in the colonic lamina propria of a histocompatible, immunodeficient host elicits a pancolitis that morphologically mimics human UC.

CD56/neural cell adhesion molecule expression in primary extranodal Ki-1/CD30+ lymphoma. Report of a pediatric case with simultaneous cutaneous and bone localizations

We describe the clinicopathologic features of an unusual case of CD30+/CD50+ T-cell lymphoma in a child who presented with simultaneous primary extranodal cutaneous and bone localizations. The expression of CD56 (neural cell adhesion molecule, or NCAM) is rare in non-Hodgkin's lymphomas other than in a group of haematopoietic/lymphoid neoplasms of natural killer and natural killer-like T-cells, which usually involve extranodal sites and often pursue an aggressive clinical behavior. Coexpression of CD30 and CD56 in T-cell lymphomas is exceedingly rare, and its biological significance is unknown. Our patient responded well to an intensive chemotherapy regimen, and she is now in complete remission 4 years after discontinuation of chemotherapy. Expression of NCAM could be regarded as responsible, in part, for the extranodal localization of lymphoma cells; expression of CD56 also might contribute to the definition of a subset of CD30+ lymphomas with distinctive clinicopathologic features.

[CD95 (APO-1/Fas) and CD95-ligand (CD95L). Implications of these apoptosis mediating receptor/ligand systems in the pathogenesis of autoimmune diseases]

The CD95 (APO-1/Fas) receptor mediates programmed cell death in apoptosis sensitive cells upon oligomerization either by CD95 antibody or by its natural ligand, CD95 ligand (CD95 L). Studies on tissue distribution have shown that CD95 is broadly expressed in normal adult tissues. Furthermore, the spectrum of CD95-expressing cells in inducibly enlarged in the context of chronic inflammation. In contrast, the number of cells capable of expressing CD95 L is strikingly limited to small subsets of lymphocytes and histiocytes and to some specialized normal epithelia. This suggests that cell death via this receptor/ligand system, although possible in almost every tissue and cell type, is limited to very special scenarios one of which is chronic lymphohistiocytic inflammation. The lpr/lpr mouse and the gld/gld mouse are well-known models for autoimmune disorders. Both mutants have abnormal B and T lymphocytes and high titers of autoantibodies. Recently, these mice have been discovered to have functional defects in the murine equivalents of human CD95 and CD95 L, respectively. This suggests that the CD95/CD95 L system might act by preventing autoimmune disease, e.g., by preventing emergence of autoreactive T and B lymphocytes. A human homologue of the lpr mutation has been described as autoimmune lymphoproliferative syndrome. We show that, in mice, CD95/ CD95 L might be operative in experimental graft versus host disease. Further, we suggest a role of this system in early steps of ulcerative colitis. Considering our observations against the background of current literature, CD95/CD95 L is likely to play a dual role in induction and maintenance of peripheral tolerance on the one hand and in tissue damage by chronic inflammation on the other.

Expression of APO-1 (CD95), a member of the NGF/TNF receptor superfamily, in normal and neoplastic colon epithelium

APO-1 is a 48-kDa cell-membrane protein identical to the Fas antigen now designated CD95. It is a member of the NGF/TNF receptor superfamily. Anti-APO-1 monoclonal antibody induces apoptosis in a variety of cell types expressing this antigen. We immunohistochemically investigated APO-1 expression in normal colon mucosa, 20 adenomas, 258 colon carcinomas and 10 liver metastases and carried out in vitro studies using a panel of colon-carcinoma cell lines. Immunohistochemically, APO-1 was regularly expressed at the basolateral membrane of normal colon epithelia. In a minor fraction of colon adenomas and in 39.1% of colon carcinomas APO-1 expression was diminished and in 48.1% of carcinomas, predominantly of the non-mucinous type, APO-1 expression was completely abrogated. The normal level of APO-1 in carcinomas was correlated with the mucinous type. Reduced/lost APO-1 expression was more frequent in rectal carcinomas. Complete loss of APO-1 was more frequent in tumors that had already metastasized. APO-1 expression in liver metastases essentially corresponded to that of the primary tumors. Comparative analysis with data from previous studies revealed that the mode of APO-1 expression is correlated with that of HLA-A,B,C./beta 2m, HLA-DR, HLA-D-associated invariant chain and of the secretory component. Surface expression of APO-1 was heterogeneous in colon-carcinoma cell lines; SW480 expressed considerable amounts of APO-1 on all cells, while HT-29 constitutively did less so and only in a minority of cells. Surface density of APO-1 and the fraction of positive cells in HT-29 was enhanced by interferon-gamma (IFN-gamma) and, additively, by tumor necrosis factor-alpha (TNF-alpha), whereas in SW480 APO-1 expression was not modulated by these cytokines. We conclude that neoplastic transformation of colon epithelium often leads to a loss of the physiologic, high level of surface APO-1 by giving rise either to a stable lack of APO-1 or to an IFN-gamma/TNF-alpha-sensitive phenotype of inducible APO-1 expression.

Constitutive and induced expression of APO-1, a new member of the nerve growth factor/tumor necrosis factor receptor superfamily, in normal and neoplastic cells

BACKGROUND

APO-1 is a 48 kilodalton transmembrane, cysteine-rich glycoprotein identical with the Fas antigen which belongs to the nerve growth factor/tumor necrosis factor receptor superfamily. Cross-linking of APO-1 induces apoptotic cell death in sensitive cells.

EXPERIMENTAL DESIGN

As suggested by our preliminary results, APO-1 expression is not restricted to cells of the hematopoietic lineage. We therefore investigated APO-1 expression in normal human tissues and in various epithelial and nonepithelial tumors.

RESULTS

We show by immunohistochemistry that APO-1 is a non-lineage antigen constitutively expressed in a variety of epithelial cells. This includes the basal layers of various squamous epithelia, transitional epithelium and columnar epithelium of the biliary tract and intestine. Among the epithelial cell types of the reproductive system of both genders, APO-1 expression is complex. Except the satellite cells of autonomic ganglia, all cells of the nervous tissue are APO-1-negative. Among mesenchymal cells, constitutive APO-1 expression is rare but detectable in various kinds of activated cells, e.g. fibroblasts, osteoblasts, and subpopulations of endothelial cells. Within the immune system, APO-1 is broadly distributed among histiocytic cells but restricted to minor subpopulations of peripheral T and B cells. Immature T cells, i.e., thymocytes, do not express detectable APO-1-antigen. Expression of APO-1 was induced in phytohemagglutinin activated T cells and in a mammary carcinoma cell line by interferon-gamma alone and in combination with tumor necrosis factor alpha. Consistently, there was an in situ induction of APO-1 in several types of glandular epithelium in microtopographic association with lymphohistiocytic infiltrates. This inflammation-associated APO-1 induction went along with increased expression of this molecule within the lymphocytic compartment of the lesion. In tumors. APO-1 expression was heterogeneous. In comparison to their normal counterparts, some tumors showed abnormal hypo-expression or loss of APO-1. However, abnormal neo-expression was also found.

CONCLUSIONS

Tissue distribution, in vitro expression, and reaction upon cytokine-induced activation suggest that APO-1 might not only transmit apoptotic signals but might play a more general role in growth control.

Coregulation of the APO-1 antigen with intercellular adhesion molecule-1 (CD54) in tonsillar B cells and coordinate expression in follicular center B cells and in follicle center and mediastinal B-cell lymphomas

APO-1 is a 48-Kd transmembrane glycoprotein identical to the Fas antigen and belongs to the nerve growth factor (NGF)/tumor necrosis factor (TNF) receptor family of surface molecules. Cross-linking of APO-1 induces apoptotic cell death in sensitive cells. We show here that APO-1 is an activation molecule on B cells. It was induced/enhanced on dense and buoyant tonsillar B cells, respectively, through surface Ig cross-linking in combination with interleukin-2 or by interferon-gamma together with tumor necrosis factor-alpha. These conditions also increased the amount of intercellular adhesion molecule-1 (CD54) on these cells. Epstein-Barr virus transformants of peripheral B cells coexpressed APO-1 and CD54 at very high levels. Immunohistologically, Apo-1 was detectable at low levels in a subpopulation of follicle center B blasts and, at higher levels, in sinusoidal B cells. APO-1 was undetectable in follicular mantle B cells and plasma cells. In isolated tonsillar B cells, APO-1 was expressed in CD10+ follicle center cells. In acute B lymphoblastic leukemia, chronic B lymphocytic leukemia, and Burkitt's lymphomas, APO-1 and CD54 molecules were immunohistochemically undetectable. Coordinate expression of these antigens was found in mediastinal B-cell lymphomas. The mode of APO-1 and CD54 expression was correlated in follicle center cell lymphomas (P < .0019), but less stringently in hairy cell leukemia. No association was found in plasmacytomas. This was in line with the differential expression of these molecules found in reactive plasma cells. Expression of APO-1 in B cells of different stages of differentiation and, correspondingly, in certain B-cell neoplasias might suggest a role of this molecule in the induction of B-cell apoptosis. This function might be influenced by CD54 and CD54-mediated signals.

Venular endothelium binding molecules CD44 and LECAM-1 in normal and malignant B-cell populations. A comparative study

Lymphocytes leave the blood via post-capillary venules by binding initially to their specialized endothelium. CD44 is a 80-90 kDa hyaluronate-binding glycoprotein involved in binding to endothelium of high endothelial venules (HEV). LECAM-1 is a 75-85 kDa glycoprotein with lectin activity interacting with human peripheral lymph node vascular addressin (PNAd) on HEV. This immunohistochemical study shows that CD44 and LECAM-1 are essentially coordinately expressed on B-lymphocytes. The mode and level of CD44/LECAM-1 expression dissect the peripheral B-cell development into stages that are closely linked to morphologically defined B-cell compartments. Although statistically correlated in B-cell leukaemias (p < 0.0009) and extranodal B-cell lymphomas (p < 0.003), expression of both molecules was less stringently coordinated in 127 B-cell neoplasms examined. B-cell chronic lymphocytic leukaemia, hairy cell leukaemia and mantle zone lymphoma were CD44/LECAM-1 positive, thus corresponding to their reactive counterparts. Correspondingly, follicular centre cell-derived lymphomas were devoid of both markers. Conversely, CD44 and LEC-AM-1 were infrequently detectable in extranodal malignant B-cell neoplasms, irrespective of their maturational state. Presence versus absence of CD44 and LECAM-1, alone or together, determined neither the leukaemic versus aleukaemic state nor the nodal versus extranodal tumour-forming phenotype of a B-cell tumour.

Interaction of the hexamethonium derivative W84, an allosteric effector at muscarinic cholinoreceptors, with rat brain nicotinic binding sites

The hexamethonium derivative W84 (hexamethylene-bis-[dimethyl-(3-phthalimidopropyl)-ammonium bromide]) combined with atropine has an overadditive protective action against organophosphorus intoxications. It affects allosterically the binding of (-) [3H]N-methylscopolamine [(3H]NMS) to muscarinic cholinoceptors. Because nicotinic receptors are involved in organophosphorus intoxications, the interaction of W84 with nicotinic cholinoceptors was investigated. (-) [3H]nicotine (2.5 nM) was used to label nicotinic binding sites in rat brain membranes in 50 nM Tris, pH 7.3 at 23 degrees. Under control conditions, (-) [3H]nicotine-binding revealed a KD of 4 X 10(-9) M and a Bmax of 53 fmol/mg membrane protein. W84 inhibited (- ) [3H]nicotine-binding with an IC50 of 3 X 10(-5) M by reducing the binding affinity. The IC50 of hexamethonium was 20 X 10(-5) M. At 10(-4) M, W84 did not affect the dissociation rate of (-)[3H]nicotine, suggesting a lack of allosteric activity. For sake of comparison, the action of W84 was checked on [3H]NMS-binding (control: KD approximately 1 X 10(-9) M, Bmax approximately 500 fmol/mg prot). W84 inhibited the binding of [3H]NMS (0.5 nM) with an IC50 of 1.5 X 10(-9) M. At 10(-4) M, W84 prevented [3H]NMS-dissociation almost completely, thus displaying the allosteric action at muscarinic cholinoceptors. In conclusion, the results of the (-)[3H]nicotine-binding experiments point to a pure competitive action of W84 at nicotine cholinoceptors, lacking any allosteric effect. This competitive action may contribute to the protective effect of W84 in organophosphorus poisoning.