PubMed HealthSearch

Biomedical subjects

M Rowe

Publications and source records attributed to M Rowe.

At least 73 records · Page 4Linked to original sources

The application of immunoassays and fluorometry to the detection of polycyclic hydrocarbon-macromolecular adducts and anti-adduct antibodies in humans.

The metabolic activation of polycyclic aromatic hydrocarbons (PAH) to chemical species that form covalent adducts with cellular macromolecules (DNA and protein) is central to theories of carcinogenesis. Assays are currently being developed that will accurately reflect human macromolecular exposure to these carcinogens. Immunoassays are capable of detecting low levels of PAH-DNA adducts and antibodies directed against these adducts in humans and HPLC/spectrophotofluorimetry allows the detection of carcinogen-DNA or carcinogen-protein adducts in human peripheral blood. Both types of method have inherent advantages and disadvantages, and the use of more than one type of corroborative assay is a feature in our work. Simplified but highly specific synchronous fluorescence spectra have been obtained for BP-tetrols after mild acid hydrolysis and HPLC of sample materials. When using a wavelength difference of 34 nm to drive the excitation and emission monochromators simultaneously, the pyrene fluorophore, when present, has a signature peak at 345 nm (excitation). The results of immunoassays demonstrate human exposure to PAH as a class of carcinogen, since serological cross-reactivity of antibodies does not limit detection in this system to a single chemical compound. In addition the formation in humans of anti-PAH-DNA antibodies has been shown, presumably in response to both past and present exposure to the parent compounds. In summary the results of each assay can indicate human exposure to PAH and have the potential for molecular dosimetry of this exposure.

Antibodies

Characterization of the serological response in man to the latent membrane protein and the six nuclear antigens encoded by Epstein-Barr virus.

A total of 116 sera from healthy individuals and from patients with Burkitt's lymphoma (BL), nasopharyngeal carcinoma (NPC) or rheumatoid arthritis (RA) were studied with respect to antibody responses to each of the seven known transformation-associated Epstein-Barr virus (EBV)-encoded antigens [latent membrane protein (LMP) and six nuclear proteins (EBNAs 1 to 6)]. The antibodies were detected using modified standard immunoblotting techniques. Antibodies to LMP were detected for the first time in sera from 6/27 (22%) healthy, EBV-immune individuals (seropositive for the viral capsid antigens). An increased incidence of anti-LMP antibodies was found in EBV-immune sera from patients with BL (17/24 positive; 71%), NPC (21/33; 64%), and RA (16/21; 76%). Antibodies to EBNA 1 were detected in all EBV-immune sera at a standard 1:20 dilution. Antibodies to the other EBNAs were detected in only a proportion of these sera (20 to 95%) at the same dilution. Only minor disease-associated differences in the incidence of these antibodies were observed, the most consistent being that RA sera had a higher incidence of antibodies to EBNAs 2 to 6 compared with healthy controls. Testing of the sera at a 1:100 dilution suggested that there were some disease-related differences in the titres of anti-EBNA antibodies. At this serum dilution, a reduced incidence of antibodies to EBNA 2 was seen in NPC (6/31) compared with RA (18/19) and healthy EBV-seropositives (16/26); antibodies to EBNA 3 were detected at an increased incidence in BL (8/15) and NPC (16/31) compared with control sera (7/26); antibodies to EBNA 4 were detected at increased incidence in BL (5/15) and RA (6/19) compared with control sera (1/26); and antibodies to EBNA 6 were detected at increased incidence in NPC (19/31) and RA (7/19) compared with control sera (3/26).

AIDS-Related Complex

Epstein-Barr virus-specific cytotoxic T-cell recognition of transfectants expressing the virus-coded latent membrane protein LMP.

Cytotoxic T cells from Epstein-Barr virus (EBV)-immune individuals specifically kill EBV-transformed B cells from HLA class I antigen-matched donors even though the latently infected cells express only a restricted set of virus genes. The virus-induced target antigens recognized by these immune T cells have not been identified. In our experiments, EBV DNA sequences encoding the virus latent gene products Epstein-Barr nuclear antigen (EBNA)1, EBNA 2, and EBNA-LP and the latent membrane protein (LMP) were individually expressed in a virus-negative human B-lymphoma cell line, Louckes. Transfected clones expressing LMP were killed by EBV-specific cytotoxic T-cell preparations from each of three virus-immune donors HLA matched with Louckes through HLA-A2, B44 antigens; control transfectants or clones expressing one of the EBNA proteins were not recognized. Expression of LMP in a second virus-negative B-cell line, BL41, sensitized these cells to EBV-specific cytolysis restricted through the HLA-A11 antigen. To distinguish between the viral protein and an induced human B-cell activation antigen as the target for T-cell recognition, LMP was then expressed in a murine mastocytoma cell line, P815-A11-restricted human T cells. The LMP-expressing P815-A11 transfectants were susceptible to lysis by EBV-specific cytotoxic T cells from three HLA-A11-positive individuals. Both Louckes and P815-A11 cells were also transfected with constructs capable of encoding a truncated form of LMP (Tr-LMP) which lacks the N-terminal 128 amino acids of the full-length protein. Tr-LMP-expressing transfectants were not recognized by the above T-cell preparations. The results suggest that LMP, and, in particular, epitopes derived from the N-terminal region of the protein, provides one of the target antigens for the EBV-induced human cytotoxic T-cell response.

Animals

Different patterns of Epstein-Barr virus gene expression and of cytotoxic T-cell recognition in B-cell lines infected with transforming (B95.8) or nontransforming (P3HR1) virus strains.

Epstein-Barr virus (EBV)-negative Burkitt's lymphoma (BL) cell lines have been converted to EBV genome positivity by in vitro infection with the transforming EBV strain B95.8 and with the nontransforming mutant strain P3HR1, which has a deletion in the gene encoding the nuclear antigen EBNA2. These B95.8- and P3HR1-converted lines have been compared for their patterns of expression of EBV latent genes (i.e., those viral genes constitutively expressed in all EBV-transformed lines of normal B-cell origin) and for their recognition by EBV-specific cytotoxic T lymphocytes (CTLs), in an effort to identify which latent gene products provide target antigens for the T-cell response. B95.8-converted lines on several different EBV-negative BL-cell backgrounds all showed detectable expression of the nuclear antigens EBNA1, EBNA2, and EBNA3 and of the latent membrane protein (LMP); such converts were also clearly recognized by EBV-specific CTL preparations with restriction through selected human leukocyte antigen (HLA) class I antigens on the target cell surface. The corresponding P3HR1-converted lines (lacking an EBNA2 gene) expressed EBNA1 and EBNA3 but, surprisingly, showed no detectable LMP; furthermore, these converts were not recognized by EBV-specific CTLs. Such differences in T-cell recognition were not due to any differences in expression of the relevant HLA-restricting determinants between the two types of convert, as shown by binding of specific monoclonal antibodies and by the susceptibility of both B95.8 and P3HR1 converts to allospecific CTLs directed against these same HLA molecules. The results suggest that in the normal infectious cycle, EBNA2 may be required for subsequent expression of LMP and that both EBNA2 and LMP (but not EBNA1 or EBNA3) may provide target antigens for the EBV-specific T-cell response.

Antigens, Viral

The level of expression of class-I MHC antigens in adenovirus-transformed human cell lines.

The level of expression of the class-I major histocompatibility (MHC) antigen was determined in a series of human embryo cell lines transformed with either adenovirus 12 (Ad 12) early region I (EI) or adenovirus 5 (Ad 5) EI DNA or with combinations of Ad 12 early region IA (EIA) or Ad 2 EIA with activated N-ras DNA. MHC class-I antigen expression was greatly reduced in all Ad 12 transformants, compared to primary cells. Expression was also reduced in the Ad 5 cell lines transformed with EIA and EIB DNA, but levels were near normal in those lines with only EIA DNA present. Amounts of MHC class-I antigen on the cell surface, as determined by RIA and FACS analysis, generally reflected total cellular levels as determined by Western blotting. Expression of beta 2 microglobulin was also much reduced in those cell lines with low levels of MHC class-I antigen. The treatment of primary cells and all the transformants with human gamma-interferon resulted in increased expression of HLA on the cell surface. Infection of primary human cells with Ad 12 or with a series of Ad 12 mutants did not have any effect on the MHC class-I antigens present.

Adenovirus Early Proteins

Epstein-Barr virus-specific T-cell recognition of B-cell transformants expressing different EBNA 2 antigens.

Epstein-Barr (EB) virus isolates can be classified as type A or type B depending upon the identity of the virus-encoded nuclear antigen EBNA 2; the EBNA 2A and 2B proteins show limited amino-acid homology and induce largely non-cross-reactive antibody responses in humans. To examine whether EBNA 2 might also be a target for virus-specific cytotoxic T-cell responses (like "intracellular" antigens in other viral systems), normal B cells from non-immune donors of known HLA type were transformed in vitro with virus isolates either of type A (from the B95-8 and IARC-BL74 cell lines) or of type B (from the AG876 and IARC-BL16 cell lines) to provide a suitable panel of target cells. DNA hybridization with type-specific probes and immunoblotting with type-specific antisera confirmed the EBNA 2 type of the resident virus in the various in vitro transformants. These cells were then tested as targets for virus-specific cytotoxic T cells, the latter being prepared from type-A virus-infected donors by in vitro reactivation of memory cells from peripheral blood using autologous type-A virus-transformed cells as stimulators. Such effector cells lysed type-A virus-transformed and type-B virus-transformed target cells equally well, indicating that EBNA 2 (in particular that part of the protein which varies between virus types) seems not to be a dominant antigen for the induction of EB virus-specific cytotoxic responses.

Antibodies, Monoclonal

Epstein-Barr virus-transformed human precursor B cell lines: altered growth phenotype of lines with germ-line or rearranged but nonexpressed heavy chain genes.

A series of lymphoblastoid cell lines (LCLs) have been established by in vitro infection of fetal bone marrow and fetal liver cells with Epstein-Barr virus (EBV). While most lines showed the usual mature B cell phenotype, a small proportion were cytoplasmic and surface immunoglobulin (Ig) heavy and light chain negative. Analysis of gene rearrangements indicated that the Ig- lines were either germ-line or nonproductively rearranged when probed for JH and were in germ-line configuration for C chi; no mu or chi mRNA could be detected in such cells. Precursor B cell lines were indistinguishable from their normal Ig+ counterparts in their expression of a wide variety of cell surface markers including "activation" antigens usually associated with the lymphoblastoid state; even the single LCL showing germ-line heavy and light chain genes expressed B lineage-specific cell surface antigens. However, the Ig- lines were distinct from their Ig+ counterparts in three important respects: (a) they grew much more slowly and achieved lower saturation densities, (b) they showed unusually high proportions (8-16%) of cells in EBV-productive cycle, and (c) they contained unusually high proportions (up to 40%) of cells expressing free joining (J) chain. These results suggest that precursor B cells differ in their response to the growth-transforming effects of EBV such that the virus-cell interaction in precursor B cell lines is inherently less stable than in conventional LCL. In particular there may be a greater movement of cells out of cycle and along the B cell maturation pathway. It is possible that such movement leads in individual cells either to virus replication or to a "sterile" plasmacytoid differentiation with J chain expression in the absence of Ig synthesis.

Antibody Formation

Differences in B cell growth phenotype reflect novel patterns of Epstein-Barr virus latent gene expression in Burkitt's lymphoma cells.

Recently established Epstein-Barr virus (EBV)-positive Burkitt's lymphoma (BL) cell lines, carrying chromosomal translocations indicative of their malignant origin, have been monitored for their degree of in vitro progression towards a more 'lymphoblastoid' cell surface phenotype and growth pattern, and for their expression of three EBV latent gene products which are constitutively present in all virus-transformed normal lymphoblastoid cell lines (LCLs). BL cell lines which stably retained the original tumour biopsy phenotype on serial passage were all positive for the nuclear antigen EBNA 1 but did not express detectable amounts of two other 'transforming' proteins, EBNA 2 and the latent membrane protein (LMP). This novel pattern of EBV gene expression was also observed on direct analysis of BL biopsy tissue. All three viral proteins became detectable, however, in BL cell lines which had progressed towards a more LCL-like phenotype in vitro. This work establishes a link between B cell phenotype and the accompanying pattern of EBV latent gene expression, and identifies a novel type of EBV:cell interaction which may be unique to BL cells.

Antibodies, Monoclonal

Epstein-Barr virus nuclear antigen 2 specifically induces expression of the B-cell activation antigen CD23.

Epstein-Barr virus (EBV) infection of EBV-negative Burkitt lymphoma (BL) cells induces some changes similar to those seen in normal B lymphocytes that have been growth transformed by EBV. The role of individual EBV genes in this process was evaluated by introducing each of the viral genes that are normally expressed in EBV growth-transformed and latently infected lymphoblasts into an EBV-negative BL cell line, using recombinant retrovirus-mediated transfer. Clones of cells were derived that stably express the EBV nuclear antigen 1 (EBNA-1), EBNA-2, EBNA-3, EBNA-leader protein, or EBV latent membrane protein (LMP). These were compared with control clones infected with the retrovirus vector. All 10 clones converted to EBNA-2 expression differed from control clones or clones expressing other EBV proteins by growth in tight clumps and by markedly increased expression of one particular surface marker of B-cell activation, CD23. Other activation antigens were unaffected by EBNA-2 expression, as were markers already expressed on the parent BL cell line, including BL markers (cALLA and BLA), proliferation markers (transferrin receptor and BK19.9), and cell adhesion-related molecules (LFA-1 and LFA-3). Increased CD23 expression in cells expressing EBNA-2 was apparent from monoclonal anti-CD23 antibody binding to the cell surface, from immunoprecipitation of the 45-kDa and 90-kDa CD23 proteins with monoclonal antibody, and from RNA blots probed with labeled CD23 DNA. The results indicate that EBNA-2 is a specific direct or indirect trans-activator of CD23. This establishes a link between an EBV gene and cell gene expression. Since CD23 has been implicated in the transduction of B-cell growth signals, its specific induction by EBNA-2 could be important in EBV induction of B-lymphocyte transformation.

Antigens, Viral

Monoclonal antibodies to the latent membrane protein of Epstein-Barr virus reveal heterogeneity of the protein and inducible expression in virus-transformed cells.

Monoclonal antibodies specific for the 'latent membrane protein' (LMP) of Epstein-Barr virus (EBV), one of the effector proteins of EBV-induced B cell transformation, have been generated from mice immunized with a beta-galactosidase fusion protein containing the carboxyl half of the B95.8 strain LMP sequence. Four monoclonal IgG1 antibodies, designated CS.1, CS.2, CS.3 and CS.4, which together recognized at least three different epitopes on the molecule, were used to examine various aspects of LMP expression in B cell lines transformed in vitro. The pooled CS.1 to 4 reagent detected the LMPs encoded by each of 20 geographically distinct EBV isolates, despite a degree of inter-isolate heterogeneity in the size and antigenicity of the protein. In cell lines carrying the prototype B95.8 virus strain, particularly if these were virus producers, an additional lower molecular weight LMP was also detected; this appeared to correspond to the truncated form of the protein already predicted to exist from the analysis of B95.8 lytic cycle mRNAs. Attempts were made to identify an analogous truncated form of LMP in cell lines carrying other virus isolates after treatment with phorbol ester and/or sodium butyrate to induce virus production. Surprisingly these experiments showed that expression of the full length LMP molecule was itself strongly inducible by these agents; when monitored at the single cell level, this was a generalized response and was not restricted to cells entering a lytic cycle. Expression of LMP in EBV-transformed B cells therefore appears to be subject to a distinct type of regulation.

Antibodies, Monoclonal

Monoclonal and polyclonal antibodies against Epstein-Barr virus nuclear antigen 5 (EBNA-5) detect multiple protein species in Burkitt's lymphoma and lymphoblastoid cell lines.

The Epstein-Barr virus nuclear antigen 5 (EBNA-5) is encoded by highly spliced mRNA from the major IR1 (BamHI-W) repeat region of the virus genome. A mouse monoclonal antibody, JF186, has been raised against a synthetic 18-amino-acid peptide deduced from the EBNA-5 message of B95-8 and Raji cells. The antibody showed characteristic coarse nuclear granules by indirect immunofluorescence and revealed multiple EBNA-5 species by immunoblotting and immunoprecipitation. The B95-8 line itself and all B95-8 virus-carrying cells, whether lymphoblastoid cell lines or in vitro-converted sublines of Epstein-Barr virus (EBV)-negative Burkitt's lymphoma (BL) lines, were EBNA-5 positive. Among 36 cell lines carrying different EBV strains, only 10 expressed the B95-8-Raji-prototype EBNA-5 recognized by JF186; this was probably due to genetic variation in the epitope recognized by JF186, as shown for P3HR-1. Human antibodies, affinity purified against EBNA-5-JF186 immunoprecipitates, detected EBNA-5 in the majority of EBV-positive BL lines and in all lymphoblastoid cell lines containing the BL-derived viruses. Thus, EBNA-5 can be expressed by all virus isolates examined, but is down-regulated, together with other latent gene products, in a minority of BL lines which have a particular cellular phenotype. EBNA-5 was detected as a ladder of protein species of 20 to 130 kilodaltons (kDa), with a regular spacing of 6 to 8 kDa, consistent with the coding capacity of the combined BamHI-W 66- and 132-base-pair exons, together with shifts of 2 to 4 kDa, consistent with the size of the separate 66- and 132-base-pair exons. Multiple EBNA-5 proteins can be expressed by the single cell as shown by cloning of newly infected cells.

Animals

Influence of the Epstein-Barr virus nuclear antigen EBNA 2 on the growth phenotype of virus-transformed B cells.

Epstein-Barr virus (EBV) isolates show sequence divergence in the BamHI YH region of the genome which encodes the nuclear antigen EBNA 2, a protein thought to be involved in the initiation of virus-induced B-cell transformation; type A isolates (such as B95-8 EBV) encode a 82- to 87-kilodalton EBNA 2A protein, whereas type B isolates (such as AG876 EBV) encode an antigenically distinct 75-kilodalton EBNA 2B protein. In the present work 12 type A isolates and 8 type B isolates have been compared for their ability to transform resting human B cells in vitro into permanent lymphoblastoid cell lines. Although the kinetics of initial focus formation was not markedly dependent upon the EBNA 2 type of the transforming virus, on subsequent passage type A virus-transformed cells (type A transformants) yielded cell lines much more readily than did type B transformants. Direct comparison between the two types of transformant revealed clear differences in several aspects of growth phenotype. Compared with type A transformants, cell lines established with type B virus isolates consistently displayed an unusual growth pattern with poor survival of individual cells shed from lymphoblastoid clumps, a lower growth rate and a greater sensitivity to seeding at limiting dilutions, and a significantly lower saturation density that could not be corrected by supplementation of the medium with culture supernatant containing B-cell growth factors. This is the first direct evidence that, in EBV-transformed B-cell lines, the EBNA 2 protein plays a continuing role in determining the cellular growth phenotype.

Alleles

Epstein-Barr virus status and tumour cell phenotype in sporadic Burkitt's lymphoma.

Burkitt's lymphoma (BL) biopsy cells and derived cell lines can be grouped according to their patterns of reactivity with 6 selected monoclonal antibodies (MAbs) against B cell-associated surface antigens. Group I cells react only with MAbs J5 and 38.13, recognising the common acute lymphoblastic leukaemia antigen and a BL-associated antigen respectively; group II cells react with J5 and 38.13 and with one or more of a set of MAbs (Ki-24, MHM6, AC2, Ki-1) against "lymphoblastoid" antigens; group III cells react only with these anti-"lymphoblastoid" MAbs. Tumour biopsy cells from 17 cases of sporadic BL, 9 positive for the Epstein-Barr (EB) virus genome and 8 negative, have been analysed during the process of cell line establishment in vitro. In early passage the EB virus-negative BL cells showed either a group I phenotype or gave an additional reactivity with MAb Ki-24 which placed them in group II; these phenotypes remained essentially stable with continued growth of the cell lines for up to 50 passages. By contrast the EB virus-positive BL cells were much more susceptible to phenotypic change in vitro. Although such cells displayed a group I or group II phenotype in early passage, many of the lines soon moved into group III whilst retaining the karyotypic markers indicative of their malignant origin. These observations suggest that a resident EB virus genome can drive the in vitro progression of BL cells towards a more "lymphoblastoid" phenotype. This was confirmed in subsequent experiments where virus-negative BL cell lines were converted to EB virus positivity by in vitro infection. Clearly, therefore, phenotypic analysis of long-established lines can lead to false distinctions being drawn between the EB virus-positive and -negative forms of sporadic BL; both may derive from the same sub-population of target B cells in vivo.

Adolescent

Ligation of the CD23,p45 (BLAST-2,EBVCS) antigen triggers the cell-cycle progression of activated B lymphocytes.

CD23,p45 (BLAST-2,EBVCS) is a 45-kDa lineage-restricted antigen which appears on the surface of human B cells shortly after activation. A monoclonal antibody (MHM6) to CD23,p45, as well as a polyclonal rabbit antibody raised against the purified antigen were found to promote DNA synthesis in purified tonsillar B cells which had been activated with phorbol ester. Interleukin 1, which was not, by itself, stimulatory for either resting or activated B cells, significantly augmented the growth-promoting properties of MHM6. Kinetic studies indicated that while MHM6 exerted its influence in early G1, interleukin 1 acted later in the cycle just prior to the entry of cells into S phase. The findings demonstrate a role for CD23,p45 in triggering the progression of activated B lymphocytes through the G1 phase of the cell cycle. The possibility that this antigen serves as a receptor for a B cell stimulatory factor is discussed.

Animals

Evidence for an association between CD23 and the receptor for a low molecular weight B cell growth factor.

Low molecular weight B cell growth factor (BCGF) and a monoclonal antibody (MHM6) to the 45-kDa, B lineage-restricted, CD23 activation antigen (BLAST-2; EBVCS) were found to be indistinguishable in their biological effects. Individually, both augmented DNA synthesis in activated, but not resting, B lymphocytes while no additional enhancement resulted from using the two agonists in combination. Furthermore, by increasing the expression of Tac, both MHM6 and BCGF promoted activated B cells to respond more vigorously to the late addition of recombinant interleukin 2. The presence of BCGF during B cell activations was found to down-regulate the expression of the CD23 antigen while the coating of activated cells with MHM6 antibody diminished their capacity to absorb BCGF activity. The findings demonstrate that CD23 and a low molecular weight BCGF deliver a comparable growth-promoting signal to activated B cells. A possible relationship between CD23 and the receptor for the low molecular weight BCGF is discussed.

Antibodies, Monoclonal

Restricted expression of EBV latent genes and T-lymphocyte-detected membrane antigen in Burkitt's lymphoma cells.

Certain newly established Epstein-Barr virus-containing Burkitt's lymphoma cell lines do not express the cytotoxic T-lymphocyte-detected membrane antigen (LYDMA) through which EBV infection is normally controlled by the host. When the EB virus recovered from these BL lines was used to transform peripheral blood lymphocytes from seronegative donors, the lymphoblastoid cell lines (LCLs) that arose were all LYDMA positive. This indicates that the LYDMA-negative nature of the BLs is not the result of a mutation in the resident viral genome but is rather a specific adaptation in those cells, perhaps permitting evasion of the host immune surveillance in tumour development. A comparison of the EBV gene expression in six LYDMA-negative and two LYDMA-positive BL lines and in their corresponding LCLs revealed that several of the BL lines did not express all of the viral gene products classically associated with latent transformation by EBV. Four out of eight cell lines showed restricted expression of the latent membrane protein (LMP) and/or the EB nuclear antigen, EBNA 2. A new level of EBV gene regulation therefore appears to be operating in some of the BL cell lines. The patterns of expression of EBV genes in the cell lines did not show any correlation with the known susceptibility of the lines to T cell killing.

Antigens, Surface

Burkitt-like lymphoma in an English child: characterisation of tumour biopsy cells and of the derived tumour cell line.

An eight year old English boy presented with an abdominal undifferentiated 'Burkitt-like' lymphoma. Lymphoma cells from ascitic fluid were cultured on a human embryo fibroblast feeder layer and, after a short lag period, a cell line (DH-BL) was established which, like the original tumour, was both negative for the Epstein-Barr nuclear antigen (EBNA) and expressed a monoclonal pattern of surface immunoglobulin (alpha lambda). DH-BL also possessed the Burkitt-related 8:14 chromosome translocation in all metaphases analysed; no other chromosomal abnormalities were present. The cell surface phenotype of the original biopsy cells and the cultured tumour cells in early passage were investigated using a panel of monoclonal antibodies to B lineage-associated antigens. These antibodies had recently been used to characterise African 'endemic' Burkitt's lymphoma (BL) biopsy cells and their derived cell lines. The cell surface phenotype of this English EBNA negative Burkitt-like lymphoma biopsy was indistinguishable from that previously shown by biopsies of EBNA positive endemic BLs. It therefore appears that both the endemic and sporadic forms of BL, as illustrated by this case, may be derived from the same subset of progenitor cells.

Abdominal Neoplasms