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K Thielemans

Publications and source records attributed to K Thielemans.

At least 91 records · Page 5Linked to original sources
PubMed1994

Evidence that the clonogenic cell in multiple myeloma originates from a pre-switched but somatically mutated B cell.

There is still much controversy about the precursor cell type in multiple myeloma (MM). Some authors claim that it is a pre-B cell, others state that it is a memory B cell or plasmablast. We have recently shown that the VDJ region of the MM immunoglobulin heavy chain gene is somatically hypermutated and antigen selected, without intraclonal variation or evolution in time. By using a patient-specific PCR approach we have now obtained evidence that the premyeloma cell can be situated in the pre-switched B-cell compartment and that heavy chain switching can occur without further somatic mutation. Based on the MM immunoglobulin sequences derived from the bone marrow, patient-specific CDR2 and CDR3 oligonucleotides were designed. B lymphocytes were separated from plasma cells based on the expression of CD19 and HLA class II or surface bound IgM using immunomagnetic beads. The expressed Ig sequences were amplified by RT-PCR using patient specific CDR2 primers and isotype specific primers (C mu, C gamma, and C alpha). Myeloma-specific Ig sequences were detected by a myeloma-specific CDR3 probe and sequenced. In one out of five cases we found in the peripheral blood clonally related IgM and IgA sequences with the same somatic mutations as the MM-IgG sequence. In another case of an IgG MM we found in the bone marrow clonally related IgA sequences with the same somatic mutations. These findings, together with the fact that myeloma-Ig genes contain somatic mutations without intraclonal variation, suggest that the clonogenic cell in multiple myeloma can originate from a pre-switched but somatically mutated B cell.

Amino Acid Sequence↗
PubMed1993

CD45RO+ memory T cells but not CD45RA+ naive T cells can be efficiently activated by remote co-stimulation with B7.

Co-stimulatory signals are absolutely required for T cell activation after TCR-MHC-peptide interaction. The most important co-stimulatory signal known so far is mediated by the interaction of CD28 on T cells with B7 on APC. Here we demonstrate that the co-stimulatory signal from the B7 molecule does not necessarily have to come from the same cell which presents antigen. Titration curves obtained by limiting the amount of anti-CD3 mAb suggests that the same amount of TCR-CD3 cross-linking is required for full T cell activation whether B7 is present on the same or on another cell, but that the kinetics of T cell activation is slower when B7 is present on a separate cell from the primary signal. Finally and most importantly we also show that CD45RO+ memory T cells, but not CD45RA+ naive T cells, can be efficiently activated when B7 is expressed on bystander cells. These findings imply that co-stimulatory activation requirements of B7 are more stringent for naive than for memory T cells, which could be an important mechanism involved in the maintenance of self-tolerance.

Animals↗
PubMed1992

Evidence that multiple myeloma Ig heavy chain VDJ genes contain somatic mutations but show no intraclonal variation.

To investigate whether somatic hypermutation occurs in multiple myeloma (MM) Ig VH region genes, we have cloned and sequenced the expressed VH genes from five cases of MM. The sequences were obtained after polymerase chain reaction (PCR) on total RNA isolated from the bone marrow, using 5' VH family-specific leader and 3' C gamma- or C alpha-specific primers. MM-specific CDR3 oligonucleotides were produced to isolate VH genes expressed by the malignant plasma cells. In all five cases, the productive Ig gene used the VH3 family. Extensive sequence analysis of multiple independent M13 clones showed no intraclonal variation with no evidence for ongoing somatic hypermutation in MM VH region genes. We were able to identify possible germline counterparts of the expressed VH genes in two cases. Comparison of these genes shows that the MM VH region genes have somatic mutations characteristic for an antigen-driven process. In the other three cases, no close homology could be found with published VH3 sequences. These findings implicate that, in MM, clonal proliferation takes place in a cell type that has already passed through the phase of somatic hypermutation.

Adult↗
PubMed1992

Immune changes induced by electroconvulsive therapy (ECT).

There is a significant increase in the percentage and absolute number of activated lymphocytes (OKT10+, IL2R1+) after ECT treatment of major depressive disorder. There is an acute decrease in the absolute number of total lymphocytes, T8+ and Leu11+ cells one hour after a single ECT.

Adult↗
PubMed1992

Ly-1 (CD5), a membrane glycoprotein of mouse T lymphocytes and a subset of B cells, is a natural ligand of the B cell surface protein Lyb-2 (CD72).

CD5 is a 67-kDa glycoprotein expressed on the cell surface membrane of all T lymphocytes and on a small proportion of B lymphocytes. The physiologic role of this Ag is still unknown. Structural and functional studies of CD5 suggest that it might act as a receptor for a positive signal. CD5-specific mAb augment CD3- or mitogen-induced T cell proliferation, IL-2 secretion, and IL-2R expression and induce a rise in intracellular [Ca2+]. In this report, we describe the purification of mouse CD5 protein (mCD5) and its use as a probe to search for the ligand of CD5. We demonstrate that mCD5 specifically interacts with the mouse B cell differentiation Ag CD72/Lyb-2. Three serologically defined allelic forms of mouse CD72/Lyb-2 can all interact with mCD5. We further show that mCD5 can interact with human CD72/Lyb-2, and similarly, that human CD5 can interact with mouse CD72/Lyb-2. These studies may have major implications for the mechanisms of T-B cell communication.

Animals↗
PubMed1992

Antigen-pulsed dendritic cells can efficiently induce an antibody response in vivo.

The aim of this study was to develop an immunization procedure avoiding external adjuvant. Data are presented showing that syngeneic dendritic cells (DC), which have been pulsed in vitro with antigen, induce a strong antibody response in mice. By contrast, antigen (Ag)-pulsed low-density B cells, although equally able to induce interleukin 2 secretion by an Ag-specific T cell hybridoma in vitro, only weakly prime the mice in vivo. Moreover, we show that the injection of Ag-pulsed DC induces the synthesis of isotypes similar to the immunoglobulin classes detected after immunization with the same Ag in complete Freund's adjuvant. Importantly, high amounts of IgG2a antibodies are produced, suggesting that T helper type 1 cells are activated. Collectively, these data indicate that DC can initiate a primary humoral response and that they may be used as physiological adjuvant in vivo.

Animals↗
PubMed1992

Bispecific antibody therapy of two murine B-cell lymphomas.

Numerous in vitro studies have shown that T lymphocytes can be targeted towards any target cell by using bispecific antibodies (bsAbs) with specificity of the CD3/TCR complex and a target cell antigen. We have produced bsAbs directed against the membrane expressed idiotype of the murine B cell lymphomas BCLI and 38C13, and murine CD3 complex. The dual specificity of the hybrid-hybridoma produced monoclonal antibodies (MAbs) could be demonstrated by flow cytometry, the induction of T cell proliferation, the induction of IL2 secretion by polyclonal T cells, and redirected lysis of the relevant target cells. Immunotherapy of tumor bearing animals demonstrated that bsAbs could efficiently target T cells towards the tumor cells, that tumor cell--T cell bridging is established in vivo, and that both T cell subsets contribute to tumor regression resulting in long-term survival and cure of the lymphomas.

Animals↗
PubMed1991

Treatment of mice bearing BCL1 lymphoma with bispecific antibodies.

Bispecific antibodies with specificity for the CD3/TCR complex of CTL and a target cell Ag can bridge both cell types and trigger cellular cytoxicity. We have produced bispecific antibodies, directed against the surface-expressed Id of the mouse BCL1 lymphoma and the mouse CD3 complex, by hybrid-hybridoma fusion. Two recombination Ig were purified to homogeneity: B1 X 7D6F, which is univalent for Id and CD3 binding and B1 X 7D6M, which is univalent for Id binding but has lost the CD3 binding because of association of the anti-CD3 H chain with the inappropriate L chain. In vitro studies indicate that bridging the TCR/CD3 complex of resting T cells with tumor IgM Id and the appropriate bispecific antibody induced proliferation and secretion of IL-2. Furthermore, in cytotoxicity assays using 51Cr-labeled tumor cells, preactivated T cells could be targeted with the bispecific antibody to give complete lysis of the Ag+ tumor. Finally, the activity of the bispecific antibody was confirmed in vivo. Animals treated i.v. with 5 micrograms of bispecific antibody 9 days after receiving BCL1 cells were cured. Furthermore, when these animals were checked at 150 days for dormant or variant tumors, as have been reported after other forms of immunotherapy in this model, none could be found. Immunotherapy experiments comparing a mixture of control antibodies with the bispecific antibody demonstrate that tumor cell-T cell bridging is established in vivo and is required for therapeutic success. These results indicate the importance of bispecific antibodies as a novel form of treatment for cancer.

Animals↗
PubMed1991

Treatment of murine B cell lymphoma with bispecific monoclonal antibodies (anti-idiotype x anti-CD3).

It has previously been reported that T lymphocytes can be targeted by using bispecific antibodies consisting of anti-target antibody and anti-CD3. In the present study, a bispecific mAb was developed by somatic hybridization of mouse hybridomas, one producing a mAb against the Id determinant of the mouse B cell lymphoma 38C13 and the other a mAb against a polymorphic determinant on murine CD3. The bispecific antibody, anti-38C13 x anti-CD3, is bi-isotypic (IgG1 x IgG2a) and was purified by ion exchange and affinity chromatography. The dual specificity of the hybrid hybridoma-produced mAb could be demonstrated by flow cytometry, the induction of T cell proliferation, the induction of IL-2 secretion by polyclonal T cells, and redirected lysis of the relevant target cells. The hybrid (bi-isotypic) Fc part of the bispecific antibodies was nonfunctional in FcR-dependent redirected lysis. In vivo studies demonstrate that this bispecific mAb could efficiently target T cells towards the tumor cells, resulting in long term survival and cure of the lymphoma.

Animals↗
PubMed1991

The B-cell surface protein CD72/Lyb-2 is the ligand for CD5.

The glycoprotein CD5 is expressed on the surface membrane of all mature T cells and a small proportion of B lymphocytes. Its exact role in immune interactions is still unknown. Studies indicate that CD5 functions both in mice and humans as a receptor, delivering co-stimulatory signals to T cells in a manner similar to CD2 (ref. 11) and CD28 (ref. 12). Anti-CD5 antibodies stimulate both T-cell proliferation mediated by CD3 in association with the T-cell receptor and secretion of interleukin-2 and expression of its receptor, as well as inducing an increase in intracellular Ca2+ concentration (refs 5-10). To identify the ligand for CD5 we purified the human CD5 protein, labelled it with biotin and used it as a probe. Here we report that CD5 specifically interacts with the cell-surface protein CD72 exclusive to B cells. This interaction is blocked by anti-CD72 antibodies, but not by any other anti-B-cell antibodies. Moreover, non-B cells (mouse L-cell fibroblasts and human Jurkat T cells) expressing a transfected human CD72 complementary DNA could bind to the CD5-biotin conjugate. The results demonstrate that the B-cell surface protein CD72 (Lyb-2 in mice) is the ligand for CD5.

Antigens, CD↗
PubMed1991

Southern blot analysis in a case of Richter's syndrome. Evidence for a postrearrangement heavy chain gene deletion associated with the altered phenotype.

Richter's syndrome (RS) can be defined as the emergence of an aggressive lymphoma in patients suffering from chronic lymphocytic leukemia (CLL). The authors performed immunophenotypic and Southern blot analysis of the peripheral blood and tissue specimen of a patient with RS. Using immunoperoxidase and immunogold-silver staining techniques and a panel of monoclonal antibodies, the authors found that the large cells characteristic of RS showed an altered immunophenotype as compared with the CLL cells and did not express mu heavy chain. Southern blot analysis revealed identical kappa light chain rearrangements in both tumoral cell populations consistent with a common clonal origin. Using the JH probe and several restriction enzymes, the authors also found evidence for a postrearrangement deletion of the heavy chain mu gene. These findings suggest that in this case of RS, a deletion of the heavy chain mu gene resulted in loss of mu expression by the larger cells that were characteristic of RS and was associated with their altered phenotype.

Blotting, Southern↗