Engaging CD19 or target of an antiproliferative antibody 1 on human B lymphocytes induces binding of B cells to the interfollicular stroma of human tonsils via integrin alpha 4/beta 1 and fibronectin.

Adhesion of B lymphocytes within the different compartments of secondary lymphoid organs is essential for the function of the humoral immune response. It is not currently known how the temporary immobilization of B cells in distinct areas of this complex microenvironment is regulated. The present study aimed at defining B cell antigens that initiate binding of B cells to human tonsil sections in situ. Engaging the B cell antigens CD19 and target of an antiproliferative antibody 1 (TAPA-1) with monoclonal antibodies induced adhesion of these B cells to the interfollicular stroma. This binding occurred through the integrin alpha 4 beta 1 on the B cell surface and via the extracellular matrix protein fibronectin expressed in the interfollicular compartment of the tonsil. Signaling through either antigen, CD19 or TAPA-1, depended on tyrosine kinases. Binding induced by engaging CD19 required an intact cytoskeleton, whereas TAPA-1-transmitted adhesion did not. We suggest that CD19 and TAPA-1 have a novel and unique function by regulating an alpha 4 beta 1/fibronectin-mediated binding of B cells to the interfollicular stroma of lymphoid tissues.

Isolated human follicular dendritic cells display a unique antigenic phenotype.

In the present study, follicular dendritic cells (FDCs) were purified to homogeneity in order to define the lineage and function of these cells. FDCs were identified by their characteristic morphology and by their expression of receptors for the third complement component, the myeloid-restricted antigen CD14, and the FDC antigen DRC-1. Unclustered FDCs displayed a unique antigenic phenotype since they expressed several B- and myeloid lineage-restricted antigens, but lacked T and NK cell antigens as well as the leukocyte common antigen. FDCs expressed adhesion molecules, including most of the VLA proteins, intercellular adhesion molecule 1 (ICAM-1), and CD11b. FDCs could be isolated to homogeneity by their intense staining with anti-CD14 using flow cytometric cell sorting. These highly purified FDCs expressed CD14 and CD21 but lacked CD20. This antigen pattern and characteristic morphology confirmed that these cells were, in fact, homogeneous FDC preparations. Analysis of polymerase chain reaction-amplified cDNA from highly purified FDCs showed no transcripts for IL-6. The isolation of homogeneous FDC populations will be important for the analysis of the functional role of FDCs within the lymphoid follicle.

MACG1, a mouse monoclonal antibody detecting a monosialoganglioside expressed in tumor-infiltrating macrophages.

MacG1 is a mouse monoclonal antibody (mAb) directed against a ganglioside, which is differentially expressed by macrophages infiltrating malignant melanomas and benign melanocytic lesions. mAb MacG1 was obtained by immunization with liposomes containing a mixture of gangliosides extracted from malignant melanoma. The antibody was selected for binding to melanoma gangliosides and for reactivity with frozen tissue sections of malignant melanoma. mAb MacG1 showed reactivity in 25 of 46 melanomas examined but in only 1 of 51 nevi tested. The mAb did not react with melanoma cells but did with cytoplasmic granules and deposits associated with large dispersed cells, which were also found in some nonmelanomatous tumors and in some lymphoid tissues. Using mAbs directed against differentiation antigens these cells were identified as macrophages. In nearly all reactive tissues MacG1-positive macrophages accounted for a minority of the total macrophages. The difference in reactivity between malignant melanomas and nevi could not be explained by the variable numbers of total macrophages in these lesions. It is suggested that mAb MacG1 may define a functionally distinct subpopulation of tumor-infiltrating macrophages. Staining of cells other than macrophages was observed in some normal and malignant neural tissues. MacG1 bound to a monosialoganglioside extracted from melanoma and reacted only with NeuAc alpha 2-3Gal beta 1-4Glc-Cer when tested with a panel of ganglioside standards.

Clinical experiences with magnetic drug targeting: a phase I study with 4'-epidoxorubicin in 14 patients with advanced solid tumors.

Anticancer drugs reversibly bound to magnetic fluids (ferrofluids) could be concentrated in locally advanced tumors by magnetic fields that are arranged at the tumor surface outside of the organism. If certain requirements are met, systemic toxicity might be minimized, and local tumor efficacy might be increased. We have conducted a Phase I clinical trial using this approach in patients with advanced and unsuccessfully pretreated cancers or sarcomas. Nine such patients received two treatment courses, 3 patients received one course, and 2 patients received three courses of magnetic drug targeting consisting of the infusion of epirubicin in increasing doses (from 5 to 100 mg/m2) that had been chemically bound to a magnetic fluid and the application of magnetic fields to the tumors for 60-120 min. In 2 of 14 patients, the same dose of epirubicin not bound to a magnetic fluid was administered systemically 3 weeks after drug targeting for intraindividual comparisons. Magnetic drug targeting with epirubicin was well tolerated. In one case, a planned second treatment was withdrawn, because of an episode of chills 130 min after infusion of the magnetic drug. Two patients received a third treatment because of good responses after the first two therapies. Based on magnetic resonance tomographic techniques, pharmacokinetics, and the histological detection of magnetites, it was shown that the ferrofluid could be successfully directed to the tumors in about one-half of the patients. Organ toxicity did not increase with the treatment, but epirubicin-associated toxicity appeared at doses greater than 50 mg/m2. Although treatment with magnetic drug targeting seems safe, improvements are necessary to make it more effective and independent of patient- or disease-related problems. A study design to compare conventional treatments with the new treatment form within one patient seems crucial to eliminate interindividual differences.

Differential adhesion pattern of B cell chronic lymphocytic leukemia cells.

Binding of B cell chronic lymphocytic leukemia (B-CLL) cells to other cells and to extracellular matrices influences the pathophysiology and the clinical presentation of the B-CLL disease. It is still unknown which adhesion pathways regulate the traffic of B-CLL cells within distinct histologic compartments of lymphoid organs. In addition, it is not yet clarified which mechanisms mediate the intercellular adhesion of B-CLL cells. The present study sought to identify the mechanisms that are involved in the binding of B-CLL cells to secondary lymphoid organs in situ and in the homotypic aggregation of these cells. B-CLL cells specifically bound to germinal centers of normal human tonsils via the adhesion pair integrin alpha4beta1/vascular cell adhesion molecule-1 (VCAM-1). Among a large panel of antibodies tested only mAbs against CD19 induced homotypic adhesion of B-CLL cells via the adhesion molecules integrin alphaL (leukocyte function antigen-1 (LFA-1)), intercellular adhesion molecule-1 (ICAM-1) and CD21. Anti-CD19-induced aggregation required protein synthesis. We hypothesize that the observed heterotypic and homotypic adhesion of B-CLL cells reflects the ability of these leukemic cells to migrate in vivo.

Chemosensitivity of B cell chronic lymphocytic leukemia and correlated expression of proteins regulating apoptosis, cell cycle and DNA repair.

B cell chronic lymphocytic leukemia (B-CLL) cannot be cured with conventional chemotherapy. This clinical enigma appears to be at least partially due to the fact that B-CLL cells are resistant to programmed cell death (apoptosis) and that they are arrested in G0/G1 phase of the cell cycle. The reasons for the dysregulation of these two key cellular events in B-CLL are unclear. The present study aimed at determining correlations between the expression levels of proteins regulating apoptosis, cell cycle and DNA repair in B-CLL cells and normal B cells. In addition, the differential sensitivity of B-CLL cells to drug-induced apoptosis was quantified. We show that in B-CLL cells levels of the death-suppressor Bcl-2 correlated positively with those of the pro-apoptotic protein Bax and of the cyclin-dependent kinase (cdk) inhibitor p27Kip1. In B-CLL cells levels of the anti-apoptotic Bcl-xL showed a positive correlation with levels of the 80 kDa regulatory component (Ku80) of the DNA-dependent protein kinase that is involved in DNA double-stranded break repair. These correlations were not detected in normal B cells. The sensitivity of leukemic cells to FLUD but not to ADM, CPM or to DEX was reduced in pre-treated patients. These data support the hypothesis that in B-CLL cells death-modulators and molecules modulating cell cycle and DNA repair are regulated in a coordinated manner. Leukemia (2000) 14, 40-46.

Efficient elimination of chronic lymphocytic leukaemia B cells by autologous T cells with a bispecific anti-CD19/anti-CD3 single-chain antibody construct.

Recently, we have shown that a novel recombinant bispecific single-chain antibody construct (bscCD19 x CD3), induces highly efficacious lymphoma-directed cytotoxicity mediated by unstimulated peripheral T lymphocytes. Functional analysis of bscCD19 x CD3 has so far been exclusively performed with human B lymphoma cell lines and T cells from healthy donors. Here we analysed the properties of bscCD19 x CD3 using primary B cells and autologous T cells from healthy volunteers or patients with B-cell chronic lymphocytic leukaemia (B-CLL). We show that bscCD19 x CD3 induces T-cell-mediated depletion of nonmalignant B cells in all four cases and depletion of primary lymphoma cells in 22 out of 25 cases. This effect could be observed at low effector-to-target (E:T) ratios and in the majority of cases without additional activation of autologous T cells by IL-2. Even in samples derived from patients heavily pretreated with different chemotherapy regimens, strong cytotoxic effects of bscCD19 x CD3 could be observed. The addition of bscCD19 x CD3 to patients' cells resulted in an upregulation of activation-specific cell surface antigens on autologous T cells and elevated levels of CD95 on lymphoma B cells. Although anti-CD95 antibody CH-11 failed to induce apoptosis in lymphoma cells, we provide evidence that B-CLL cell depletion by bscCD3 x CD3 is mediated at least in part by apoptosis via the caspase pathway.

Selection of B-cell chronic lymphocytic leukemia cell variants by therapy with anti-CD20 monoclonal antibody rituximab.

OBJECTIVE: Anti-CD20 chimeric monoclonal antibody rituximab (Mabthera; IDEC-C2B8) is currently tested in several clinical trials for the treatment of B-cell chronic lymphocytic leukemia (B-CLL). In the present study, we investigated whether rituximab therapy may select for CD20(-) subclones. MATERIALS AND METHODS: Leukemic B-CLL cells were isolated from patients with B-CLL and sensitivity to rituximab-induced cell death was examined. Levels of CD20 protein and mRNA were determined using flow cytometry and real-time PCR, respectively. Clonality analyses of leukemic cells throughout rituximab therapy were performed by GeneScan analysis of patient clone specific rearrangements of the complementarity determining region III of the heavy chain immunoglobulin. RESULTS: Cytotoxicity of rituximab in vitro did not depend on the protein levels of CD20. During therapy with rituximab CD20(+) B-CLL cells were depleted and CD20(-) leukemic cells emerged. After treatment, the initial CD20(+) B-CLL cell clone reexpanded. CD20(-) B-CLL cells retained their capacity to synthesize the CD20 molecule. CONCLUSIONS: These data support the concept that in B-CLL rituximab treatment may not lead to the emergence of CD20(-) leukemic variants. Our findings support clinical studies investigating the benefit of prolonged period of rituximab therapy in B-CLL disease.

Identification of a sulfoglycolipid epitope shared by cells of neuroectodermal and hematopoietic origin.

Monoclonal antibody (mAb) SNH.1 detects an epitope which is restricted to cells of neuroectodermal and hematopoietic origin. The mAb was obtained by immunization of a mouse with liposomes containing a crude extract of human melanoma acidic glycolipids. The SNH.1 antigen isolated from melanoma was identified as a sulfated glycolipid, closely related or identical to sulfogalactosyl-ceramide. When tested with different lipids, mAb SNH.1 reacted as well with other sulfoglycolipids. The staining of mAb SNH.1 is restricted to the cytoplasm and often localized to the perinuclear region. Therefore, the SNH.1 mAb epitope may be detectable only during the biosynthesis of sulfoglycolipids.

Enzymatic degradation in phagocytic monocytes generates the ganglioside epitope defined by antibody MacG1.

Monoclonal antibody (mAb) MacG1 was recently shown to detect a monosialoganglioside expressed in tumor infiltrating macrophages. The present study demonstrates with in vitro experiments that the MacG1 epitope is generated during cellular digestion in phagocytic monocytes. Following phagocytosis and degradation of MacG1 negative sheep red blood cells, the MacG1 epitope was expressed in intracytoplamsic granules of murine plastic-adherent peritoneal cells. Stimulation of adherent cells and phagocytosis alone did not lead to the expression of the MacG1 epitope. Chloroquine, which inhibits the activity of lysosomal enzymes, prevented the generation of the MacG1 epitope. Reactivity with mAb MacG1 appears to reflect a specific step during the enzymatic degradation of gangliosides and the antibody may provide a unique tool for analyzing this pathway.

Monoclonal antibody MACG1 distinguishes between different molecular species of the ganglioside GM3.

The present study investigates the chemical structure of a ganglioside, detected by monoclonal antibody (MAb) MacG1, which reacts with intracytoplasmic granules of tumor-infiltrating macrophages. The results obtained by enzymatic hydrolysis and fast-atom bombardment-mass spectrometry reveal that MAb MacG1 reacts with a subcomponent of the ganglioside GM3 found in melanoma and bovine brain. MAb MacG1 might be a powerful tool to distinguish among GM3 species and could help to define their possibly different biological functions.

Apoptosis: implications of basic research for clinical oncology.

Recent studies have indicated a role for apoptosis in a variety of human diseases. Suppression of apoptosis contributes to carcinogenesis by several mechanisms, including facilitating the accumulation of gene mutations, permitting growth-factor-independent cell survival, promoting resistance to immune-based cytotoxicity, and allowing bypassing of cell-cycle checkpoints, which would normally induce apoptosis. Defects in apoptotic mechanisms also play an important part in resistance to chemotherapy and radiation. The core machinery of the cell death pathway can be reduced to a few critical types of proteins, which are well conserved across animal evolution. This review gives an update on the key players involved in apoptosis as well as an overview of the involvement of apoptosis in disease, and novel diagnostic and therapeutic options derived from the extensive basic research on this topic carried out over the last decade.

Activated T lymphocytes bind in situ to stromal tissue of colon carcinoma but lack adhesion to tumor cells.

It is not entirely clear which adhesion molecules are responsible for the site-directed traffic of T cells within the tumor microenvironment. The present study investigated whether colon carcinoma tissue and normal colon differ in the expression of functionally relevant molecules. In addition, we identified adhesion molecules involved in the binding of activated T cells onto colon carcinoma in situ. Malignant colon epithelium expressed few adhesion receptors, i.e. CD44 (HERMES), CD49b (integrin alpha2) and CD162 (PSGL-1), whereas the stromal compartment within colon carcinoma was positive for numerous binding molecules, e.g. CD44, CD49a (integrin alpha1), CD49e (integrin alpha5), CD51 (integrin alpha(v)), CD54 (ICAM-1), CD99 (MIC2) and CD162. Lymphocytes infiltrating tumor stroma contrasted with lymphocytes within normal colon interstitium by lacking CD28, CD154 (CD40L), CD56 (NCAM) and CD98 (4F2). Normal activated T cells bound to the lymphocyte-rich areas within the stroma of colon carcinoma using CD44, CD50 (ICAM-3), CD99, CD102 (ICAM-2) and CD162 on the T lymphocytes. We conclude that lymphocytes within colon carcinoma stroma may lack several functionally crucial cell surface molecules. We present a panel of adhesion molecules that could mediate the migration of activated T lymphocytes into the stroma of colon carcinoma.

Follicular dendritic cells contain a unique gene repertoire demonstrated by single-cell polymerase chain reaction.

Follicular dendritic cells (FDCs) form a dense network between B cells within the germinal center and are thought to be an important component of this B-cell microenvironment. Previous immunophenotypic studies have been inconclusive in determining the cellular origin of FDCs. Gene coexpression within individual and highly enriched FDCs was determined using polymerase chain reaction. FDCs contain a very restricted mRNA pattern with high levels of message for the C3d receptor (CR2, Epstein Barr-virus/EBV receptor, CD21) and lack of mRNA for CD20, CD45, CD4, fibronectin, and platelet-derived growth factor receptor alpha and beta. These observations are consistent with the hypothesis that FDCs may not be of classical hematopoietic or fibroblastic origin. The absence of interferon-gamma, tumor necrosis factor-alpha, interleukin-3, and interleukin-6 mRNA provides preliminary evidence that these cells might produce only a very restricted set of cytokines limited to the germinal center.

Reduced phagocytosis of apoptotic cells in malignant lymphoma.

Efficient removal of lymphocytes undergoing programmed cell death (apoptosis) by macrophages plays an important role for the proper function of normal immune system. Furthermore, in malignant lymphoma, elimination of apoptotic tumor cells by phagocytes contributes to the anti-tumor immune response. It is unknown, however, whether macrophages in normal and malignant lymphoid tissues differ in their ability to recognize and remove apoptotic cells. Our present results demonstrate that normal and malignant lymphoid tissues differ according to the extent of the infiltration by macrophages. The highest densities of macrophages (p < 0.0001) were detected in diffuse large B-cell lymphoma, centroblastic (DLBCL-CB) and immunoblastic variants and Burkitt's lymphoma. The grade of the macrophage infiltration correlated with the proliferation rates of the tumors (p < 0.0001). Compared with normal lymphoid organs, malignant lymphoma contained lower percentages of apoptotic cells phagocytosed by tissue macrophages (p < 0.001). Of all lymphomas tested, mantle cell lymphoma and DLBCL-CB expressed the lowest percentages of phagocytosed apoptotic cells (p < 0.0001).

Reduced expression of adhesion molecules and cell signaling receptors by chronic lymphocytic leukemia cells with 11q deletion.

Deletions in chromosome bands 11q22-q23 were recently shown to be one of the most frequent chromosome aberrations in B-cell chronic lymphocytic leukemia (B-CLL). Patients suffering from B-CLL with 11q deletion are characterized by extensive lymphadenopathy, rapid disease progression, and short survival times. Phenotypic and functional characteristics of B-CLL cells with 11q deletion that may help to explain the pathophysiology of this entity are yet unknown. In the present study, B-CLL cells with (n = 19) and without (n = 19) 11q deletion were analyzed for their expression of functionally relevant cell surface molecules (n = 57). B-CLL cells with 11q deletion carried significantly lower levels of the adhesion molecules CD11a/CD18 (integrin alphaL/beta2), CD11c/CD18 (integrin alphaX/beta2), CD31 (PECAM-1), CD48, and CD58 (LFA-3). Furthermore, B-CLL cells with 11q deletion expressed less the cell signaling receptors CD45 (leukocyte common antigen [LCA]), CD6, CD35 (complement receptor 1), and CD39. Reduced CD45 levels and low-level expression of CD49d correlated with decreased overall survival. B-CLL cells with or without 11q deletion did not differ in their growth fractions, expression levels of transcription factor NF-kappaB, or their response to mitogenic stimuli. Decreased levels of functionally relevant adhesion molecules and of cell signaling receptors may contribute to the pathogenesis of the subgroup of B-CLL characterized by 11q22-q23 deletion.

Differential expression of apoptosis, Bcl-x and c-Myc in normal and malignant lymphoid tissues.

Bcl-x and c-Myc have an important role for the immune response by regulating the programmed cell death (apoptosis) of lymphocytes. Dysfunction of these selection processes can lead to the development of malignant lymphoma. The present study aimed at defining the differential expression of apoptosis, Bcl-x and c-Myc in normal and in malignant lymphoid tissues. Follicular centre lymphoma (FCL-F) and mantle cell lymphoma (MCL) contained the lowest apoptotic indices (AIs), whereas Burkitt's lymphoma (BL) had the highest AIs. The AIs correlated significantly with the growth rates of the tumours and with the extent of Bcl-x expression. Bcl-x was expressed in almost all BL cells, but in few tumour cells in FCL-F and in MCL. c-Myc, in contrast, was found in the majority of the tumour cells in FCL-F and in MCL, but not in BL. Whereas the extent of Bcl-x expression correlated positively with the growth rates, an inverse correlation was observed between the percentages of c-Myc-positive tumour cells and the growth rates of the tumours. We conclude that normal and malignant lymphoid tissues have a distinct pattern of apoptosis and that expression of Bcl-x and c-Myc in B cell lymphoma is differentially regulated.

Human T lymphocytes bind to germinal centers of human tonsils via integrin alpha4/VCAM-1 and LFA-1/ICAM-1 and -2.

Binding of T lymphocytes within the different compartments of the secondary lymphoid organs is crucial for the function of the cellular and the humoral immune response. It is still not known which adhesion molecules guide T cells to the distinct areas of the lymphoid microenvironment. In the current study an in situ adhesion assay was used to define the receptors for binding of T cells to human tonsils. The T cell lines Jurkat and MOLT-4 and normal, activated T cells were found to bind exclusively to germinal centers. Jurkat cells used the receptor pair integrin-alpha4 (VLA-4alpha)/VCAM-1, whereas activated MOLT-4 cells and normal T cells bound via both adhesion pathways, namely via integrin-alpha4/VCAM-1 and LFA-1/ICAM-1 and -2. It is suggested that these adhesion mechanisms are involved in the migration of T cells into the germinal centers of secondary lymphoid organs and that they influence the selection of B cells by apoptosis.

Lymphocyte apoptosis: induction by gene transfer techniques.

Efficient gene transfer of lymphocytes has been shown to be extremely difficult. The molecular background for this gene transfer resistance is not completely understood. We reasoned that apoptosis may play a role in this gene transfer resistance of lymphocytes. We show that transfection of lymphocytes via nonviral vectors leads to induction of apoptosis in a significant proportion of cells. Since apoptosis may be mediated via the TNF alpha and TNF alpha receptor pathway, we studied the amount of TNF secreted by transfected lymphocytes. The percentage of apoptotic lymphocytes correlated well with TNF alpha secretion. TNF secretion was dependent on the gene transfection method used. High amounts of TNF secretion were detected using receptor-mediated gene transfer and lipofection. In contrast, only low amounts of TNF were detected after electroporation and retroviral gene transfer. In receptor-mediated gene transfer, TNF secretion was due to the use of anti-CD3 antibody. Induction of apoptosis and increase in necrosis was blocked using an anti-TNF antibody. This blockage led to a significant increase in the proliferation rate of lymphocytes transfected with the interleukin-2 or interleukin-7 gene. In conclusion, gene transfer techniques led to TNF secretion, apoptosis and necrosis of lymphocytes. This could be blocked using an anti-TNF antibody. Blockage of apoptosis after gene transfer should have an impact on the use of lymphocytes transfected with cytokine genes as immunologic effector cells in cancer gene therapy protocols.