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B Bogen

Publications and source records attributed to B Bogen.

At least 37 records · Page 2Linked to original sources
PubMed1998

Transient overexpression of CD4 enhances allelic exclusion of T-cell receptor (TCR) alpha chains and promotes positive selection of class II-restricted TCR-transgenic thymocytes.

CD4 contributes to antigen recognition of T cells by binding to class II MHC molecules. There is heterogeneity in expression of CD4 coreceptor among CD4+CD8+ thymocytes. We have investigated whether the expression level of coreceptor influences positive selection. Thymocytes of mice expressing transgenic lambda2(315)-Ig-light-chain/I-Ed specific TCR are poorly positively selected because they fail to allelically exclude endogenous TCR alpha chain genes and because there is no skewing towards CD4. Transient overexpression of CD4 during thymocyte development, in mice transgenic for both TCR and CD4, resulted in skewing towards CD4 in the periphery, reduced rearrangement and expression of endogenous alpha-chains, and decreased levels of thymocyte RAG-1 transcripts. Kinetic BrdU labeling experiments showed that single CD4+ thymocytes developed faster, representing the predominant population even in the cortex of the double transgenic thymi. These results demonstrate that increased coreceptor expression can compensate for poorly selectable TCR, supporting avidity and instructional models for positive selection of thymocytes.

Animals↗
PubMed1997

Rationale for adjuvant idiotypic vaccination after high-dose therapy for multiple myeloma.

With conventional therapy, multiple myeloma (MM) has a poor prognosis. During the last few years, it has become clear that high-dose chemotherapy with autologous stem cell support can increase overall survival of MM patients, but further improvement in outcome is desperately needed. The monoclonal immunoglobulin (Ig) produced by the MM cells called idiotypes (Id) is a tumor-specific antigen due to unique antigenic determinants that are localized in the variable regions of the Ig molecule. Conceivably, Id immunization of MM patients in complete remission could further increase survival. Here we review the scientific basis for such Id immunization.

Adjuvants, Immunologic↗
PubMed1996

T cells with two Tcrbeta chains and reactivity to both MHC/idiotypic peptide and superantigen.

It is thought that Tcrbeta genes are effectively allelically excluded, while Tcralpha genes are not. We report here that endogenous Tcrbeta genes are expressed on as much as 5-7% of CD4+ T cells in 8-week-old Tcralphabeta-transgenic mice. In this model, the transgenic Tcr recognizes residues 91 - 101 of a lambda2(315) Ig light chain, presented on the I-Ed class II molecule. From such mice, a CD4+ T cell clone was isolated which not only responded to lambda2(315), but also mobilized Ca2+ and proliferated in response to Mls-1a. (Inadvertently we found that the C3H/Tif substrain, in contrast to C3H/HeJ, is Mls-1a positive.) The clone expressed the transgenic Tcr (Valpha1 and Vbeta8.2), and in addition an endogenous Vbeta6 chain, conferring the Mls-1a reactivity. On the population level, 1-2% of Tcr-transgenic lymph node cells displayed Vbeta6, in addition to the transgenic beta-chain. Such dual Tcrbeta expressor cells could be preferentially expanded in vitro by first stimulating with DBA/2 spleen cells and then with lambda2(315)-pulsed BALB/c antigen-presenting cells. In addition to demonstrating that allelic exclusion of Tcrbeta-chain genes is substantial but not complete in this model, the data show that the double beta-chain expressors can have two different specificities, and be signaled through both receptors, by physiological ligands. However, such dual-Tcr T cells appear to have reduced sensitivity to ligands, due to their decreased expression of each receptor. This holds true for both early (Ca2+ mobilization) and late (proliferation) T cells activation parameters. Dual Tcr cells may have a role in the pathogenesis of autoimmune diseases: If naive T cells are first stimulated by (infectious) superantigen, they could later, as activated T cells, respond to self-peptide/MHC on costimulation-deficient cells and cause autoimmunity. As a corollary, dual Tcr Id-specific T cells could, once activated, directly regulate Id+ B cells.

Animals↗
PubMed1996

Peripheral T cell tolerance as a tumor escape mechanism: deletion of CD4+ T cells specific for a monoclonal immunoglobulin idiotype secreted by a plasmacytoma.

Tumors could escape an immune attack by inducing peripheral T cell tolerance. To test this, T cell receptor (TCR)-transgenic mice were injected with plasmacytoma cells secreting a highly tumor-specific antigen, a monoclonal immunoglobulin (Ig), for which the transgene-encoded TCR is specific. The TCR recognizes a third hypervariable region idiotypic (Id) peptide of the Ig, presented by a class II molecule on host antigen-presenting cells. The TCR-transgenic mice have previously been shown to be protected against an Id+ plasmacytoma challenge. In the present experiments, the protection was deliberately overwhelmed by subcutaneous injection of large numbers of plasmacytoma cells. Such tumor mice, chronically exposed to increasing amounts of monoclonal Ig, delete Id-specific CD4+ T cells in their peripheral lymphoid organs and in the tumor. The residual CD4+ cells express endogenous, rather than transgene-encoded TCR alpha chains. Peripheral deletion, functional T cells unresponsiveness, and thymocyte deletion are all first detected at the same serum concentration of monoclonal Ig, approximately 50 micrograms/ml (0.3 microM), and become more and more profound as the tumor burden increases. The results suggest that peripheral T cell tolerance to Id could be a tumor escape mechanism in patients with B cell malignancies. In addition, the findings have implications for T cell tolerance to Ig V regions in normal individuals.

Animals↗
PubMed1996

Dual T cell receptor T cells have a decreased sensitivity to physiological ligands due to reduced density of each T cell receptor.

A considerable fraction of T cells express two distinct T cell receptors (TCR), mainly due to expression of two TCR alpha chains. It has been suggested that such dual-TCR cells could have a role in autoimmunity. However, as such cells express less of each TCR, they could be less sensitive to their physiological ligand, i.e. peptide plus major histocompatibility complex molecules (MHC). We tested this hypothesis in a transgenic TCR model in which most T cells express different amounts of the transgene-encoded TCR, due to expression of endogenous TCR alpha chains. Five Th1 clones derived from lambda2(315) immunoglobulin light chain-specific TCR-transgenic mice expressed different levels of the transgene-encoded TCR, ranging from approximately 10,000 to approximately 50,000 TCR per cell. Cytosolic Ca2+ mobilization in single T cells from these clones elicited by lambda2(315) peptide-pulsed, I-Ed-expressing antigen-presenting cells, correlated linearly with the relative transgene-encoded TCR expression. The peptide requirement for half-maximal T cell proliferation showed a similar correlation, with low TCR levels requiring higher peptide concentration. Corroborative evidence was obtained by deployment of short-term polyclonal CD4+ lines from TCR-transgenic mice. Such lines had reduced early (Ca2+ mobilization) and late (lymphokine and proliferation) responses, compared with T cell lines from recombination-deficient TCR-transgenic severe combined immunodeficiency mice (which express only a single transgene-encoded TCR). Taken together, the Ca2+ responses increase gradually with increasing TCR expression per cell, similar to the previously described analog Ca2+ signaling elicited by increasing amounts of peptide/MHC [Røtnes et al., Eur. J. Immunol. 1994. 24: 851]. Surprisingly small reductions in TCR expression per cell reduce T cell responsiveness. This suggests that dual-TCR T cells are immunologically less effective than single-TCR T cells.

Animals↗
PubMed1996

V lambda-light chain genes reconstitute immune responses to defined carbohydrate antigens or haptens by utilizing different VH genes.

The contribution of the lambda-light chain to the development of peripheral B cell repertoire and generation of specific antibodies to haptens and polysaccharide antigens was studied in genetically manipulated kappa-deficient and lambda 2-transgenic mice. The results clearly demonstrate a non-stoichiometric VH gene family expression in the absence of k-light chain and suggest a non-stochastic pairing between VH and V lambda genes, expressed in the peripheral B cell repertoire. A shift in VH gene utilization in the case of VI lambda + antibodies was evident in response to beta 2-6 fructosan and TNP hapten. These observations demonstrate the availability of compensatory mechanisms in the absence of VK genes and are consistent with the hypothesis that VH gene family expression is controlled by genetic factors from inside the VH locus. Furthermore, genetic factors from outside the VH locus, namely restricted available light chain diversity, may lead to a shift in VH gene utilization in the peripheral B cell repertoire.

Animals↗
PubMed1995

Naive CD4+ T cells confer idiotype-specific tumor resistance in the absence of antibodies.

CD4+ T cells can recognize a processed idiotypic peptide derived from the mouse lambda 2(315) immunoglobulin light chain. The idiotypic peptide is presented on the I-E(d) class II major histocompatibility complex molecule. Mice made transgenic for a lambda 2(315)-specific alpha beta T cell receptor have been demonstrated to be specifically resistant against a tumor challenge with the MOPC315 (alpha,lambda 2(315)) plasmacytoma (Lauritzsen, G. F., Weiss, S., Dembic, Z. and Bogen, B., Proc. Natl. Acad. Sci. USA 1994, 91: 5700). That study, however, did not rule out a role of either anti-Id antibodies or T cells expressing nontransgenic specificities due to expression of endogenous T cell receptor (TcR) alpha chains. Also, the role of different T cell subsets in protection was unclear. To remove these ambiguities, we have now made the transgenic mice homozygous for the scid mutation, known to inhibit both Ig and TcR gene rearrangements. Such transgenic SCID mice lack B cells and antibodies while they still have plenty of CD4+ and CD4-8- cells expressing the transgenic alpha beta T cell receptor. The number of CD8+ T cell is dramatically reduced. Even so, transgenic SCID mice are protected against a challenge with MOPC315 plasmacytoma cells. Therefore, B cells, as well as novel T cell receptor specificities created by rearrangements of endogenous alpha-chain genes, are both dispensable for effective immunosurveillance in our system. Surprisingly, we found that transgenic CD8+ and CD4-8- cells are idiotype-specific and I-E(d) restricted. However, these T cell subsets are not required for resistance because adoptive transfer experiments demonstrated that highly purified transgenic SCID CD4+ cells suffice for tumor protection.

Animals↗
PubMed1995

Peptide phage libraries can be an efficient tool for identifying antibody ligands for polyclonal antisera.

We have examined the potential of isolating ligands for polyclonal antibodies from a nanopeptide phage library. The library was screened with a rabbit polyclonal antiserum raised against a synthetic peptide (ALWFRNHFVFGGGTKVT). Following screening, the positive phages were tested in an ELISA for their reactivity with the antiserum. Phages that showed positive reactivity with the antiserum compared with a normal rabbit serum were selected and their displayed peptides were determined. Among the 36 random positive clones, 31 clones carried the sequence AVFGGGTKL, PFFGGGSRA or APTGGSKRT that have a significant homology to the immunizing peptide. Five positive phages displayed the ATNIFIEGT sequence, which has no obvious linear homology with either the other selected peptides or with the peptide used for immunization. In contrast to the control peptide, the immunizing peptide inhibited binding of the antiserum to the peptide-displaying phages in a dose-dependent manner, thus demonstrating the specificity of the interaction. Furthermore, the rabbit B cell response to the peptide was found to be limited and focused on its C-terminal. Taken together, our data demonstrate the potential of random peptide phage libraries for defining epitopes for polyclonal antisera as well as for investigation of the nature of B cell responses to any given antigen.

Amino Acid Sequence↗
PubMed1995

Preferential positive selection of T lymphocytes which express two different TCR alpha chains, an endogenous and a transgenic.

A hallmark of positive selection in T-cell receptor (TCR)-transgenic mice is a strong skewing towards the CD4+ or the CD8+ subset, depending on the class II or I restriction of the TCR, respectively. However, previous experiments in TCR transgenic mice specific for an Ig light chain (lambda 2(315)/I-Ed class II molecule did not fit into this scheme because the authors observed an anomalous skewing towards CD8. In this paper the authors show that endogenous TCR alpha chains are expressed on > 90% of CD4+ and CD8+ cells in this particular transgenic strain, even on a selecting H-2d haplotype. Endogenous TCR alpha chains are first detected when double-positive thymocytes down-regulate either CD4 or CD8. Endogenous V alpha seems to influence generation of T-cell subsets because CD4+ and CD8+ cells express different frequencies of endogenous V alpha 2 and V alpha 8. In the absence of endogenous TCR alpha chains in recombination-deficient TCR-transgenic severe combined immunodeficiency (SCID) mice, a strong skewing towards CD4+ T cells is seen, but such mice are severely T-cell deficient. As an explanation for these results, the authors suggest that the transgenic TCR has a too low affinity for efficient positive selection, therefore, TCR alpha gene rearrangements proceed. Endogenous TCR alpha paired with transgenic TCR beta could bind to class I or class II molecules, enhance positive selection and thereby production of CD4+ or CD8+ cells. Most of the 'mismatched' CD8+ cells are lambda 2(315)-specific and I-Ed class II restricted, and may function as idiotype-specific suppressors of B cells. These results may help explain the origin of dual TCR alpha T cells. Furthermore, the authors suggest that T cells 'mismatched' for co-receptor/TCR MHC-specificity may be enriched among dual TCR alpha T cells.

Animals↗
PubMed1994

Naive idiotype-specific CD4+ T cells and immunosurveillance of B-cell tumors.

The immunosurveillance hypothesis suggests that lymphocytes can recognize tumor-specific antigens expressed by transformed cells and initiate their elimination. Immunosurveillance implies that lymphocytes of naive phenotype can home to a tumor site and become activated by tumor-specific antigens. In this study, we have employed T-cell receptor transgenic mice as a source of naive, tumor-specific T cells. The transgenic, CD4+ T cells recognize a 91- to 101-residue fragment of the lambda 2(315) immunoglobulin light chain presented by I-Ed class II molecules. Such naive, idiotype-specific, CD4+ T cells protected against tumor development of a class II negative plasmacytoma (MOPC315) and a class II positive B lymphoma (F9), which both secrete lambda 2(315) immunoglobulin. Adoptive transfer experiments demonstrated that 2 x 10(6) lymph node cells were sufficient for protection against MOPC315. Depletion of T-cell subsets indicated that transgenic CD4+ cells were indispensable for tumor resistance. However, an additional role of CD8+ T cells is not ruled out. In contrast to the resistance against the secreting MOPC315 and F9 cells, transgenic mice were not protected against B lymphoma cells (F67), which do not secrete lambda 2(315) but express a truncated lambda 2(315) chain intracellularly. The results suggest that lambda 2(315) is processed and presented by host antigen-presenting cells, which in turn activate naive, idiotype-specific T cells.

Animals↗
PubMed1994

Ca2+ mobilization in physiologically stimulated single T cells gradually increases with peptide concentration (analog signaling).

We have investigated Ca2+ mobilization in single T cells stimulated with their physiological ligand, i.e. antigenic peptide bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). Fibroblasts expressing I-Ed class II molecules were pulsed with a peptide derived from the lambda 2(315) immunoglobulin light chain. Onto such antigen-pulsed fibroblasts were sedimented cloned Th1 cells loaded with Fura-2. Changes in cytosolic Ca2+ concentration in single T cells were continually monitored by use of an imaging system based on fluorometry. Ca2+ mobilization was both peptide-specific and MHC-restricted. Within seconds of the initial APC-T cell contact, a Ca2+ spike could be observed. The Ca2+ response gradually declined over a 25-min period, during which oscillations were noted. Various parameters characterizing the magnitude of the Ca2+ response (latency, increase rate, max and mean Ca2+ increase, frequency and period of oscillations) all correlated with the amount of peptide used for pulsing the fibroblasts. Thus, Ca2+ mobilization in single T cells appears not to be an all or none phenomenon. Rather, activation is incremental (analog signaling), the degree of Ca2+ mobilization probably being related to the number of stimulatory peptide-MHC complexes on the surface of the APC. The extent of calcium mobilization and lymphokine production (interleukin (IL)-2, IL-3, interferon-gamma) correlated, at least at the population level.

Animals↗
PubMed1994

Thymic selection of immunoglobulin idiotype specific T-cells.

The thymus is the major site for differentiation and maturation of developing T-cells. The diversity in the T-cell repertoire is generated during ontogeny by rearrangements of T-cell receptor gene segments that encode clonally distributed receptors. Most of the newly produced thymocytes that bear alpha beta TCR die in the thymus as a consequence of at least two selective processes. Those that can react to self MHC antigens survive (positive selection), but only if the binding affinity for the same or other self MHC (probably complexed with self peptides) molecules is not too high (negative selection). As a result, each T-cell that has acquired functional competence in the thymus should have a certain degree of self-MHC specificity. Our comprehension of thymic development has been aided by the study of transgenic mice that bear functionally rearranged TCR or Ig lambda light chain genes. To study positive selection we analyzed transgenic mice with alpha beta TCR genes isolated from a T-cell clone specific for an idiotypic peptide of lambda 2(315) (a mutant of the lambda 2 Ig chain) bound to the E(d) MHC class II molecule. The results suggest that positive selection of some thymocytes might be weak, reminiscent of a 'struggle for survival', since the selected population was small and had high levels of transgenic receptor and coreceptor (CD4) molecules. The thymic tolerance mechanism was also investigated using a combination of both TCR and lambda 2(315) transgenic mice. The clonal deletion of Id specific thymocytes was influenced by the production site as well as the concentration of the lambda 2(315) antigen. In conclusion, the interaction avidity of a single thymocyte, which is important for selective processes, might be affected by the expression levels of each interacting component: TCR, CD4 or CD8 and MHC molecule and self antigen.

Animals↗
PubMed1993

The role of idiotype-specific, CD4+ T cells in tumor resistance against major histocompatibility complex class II molecule negative plasmacytoma cells.

It is known that immunoglobulins can be processed and that idiotypic peptides are presented on MHC class II molecules to T cells. It has also been demonstrated that T cells can recognize a complex of an Id-peptide/MHC molecule as a tumor-specific antigen on B lymphoma cells. However, plasmacytomas, an important type of B cell malignancies, most often lack class II molecules and are thus expected to be poor targets for Id-specific, CD4+ T cells. Nevertheless, we now demonstrate that cloned, MHC class II restricted T cells, specific for a lambda 2(315) idiotypic peptide, convey protection in vivo (Winn assay) against the class II molecule-negative MOPC315 (alpha, lambda 2(315)) plasmacytoma. T cells can also inhibit the growth of MOPC315 cells in vitro provided that MHC compatible (H-2d) splenocytes and extra lambda 2(315) are added. Based on these data we suggest that the myeloma protein secreted by MOPC315 cells attains such a high local concentration in vivo that it is processed and presented by neighboring host APC to the Id-specific T cells. Such activated T cells secrete lymphokines which may directly affect the growth of MOPC315 cells in the vicinity. Alternatively, lymphokines from activated T cells stimulate local host cells, like macrophages, to become tumoricidal.

Animals↗
PubMed1993

Clonal deletion of specific thymocytes by an immunoglobulin idiotype.

We have investigated whether immunoglobulin can induce clonal deletion of thymocytes by employing two strains of transgenic mice. One strain is transgenic for an alpha/beta T cell receptor (TCR) which recognizes a processed idiotypic peptide of the lambda 2(315) light chain variable region, bound to the I-Ed class II major histocompatibility complex molecule. The other mouse strain is transgenic for the lambda 2(315) gene. Double transgenic offspring from a TCR-transgenic female mated with a lambda 2(315) transgenic male exhibit a pronounced clonal deletion of CD4+CD8+ thymocytes. Analysis of neonates from the reciprocal (lambda 2(315)-transgenic female x TCR-transgenic male) cross suggests that the deletion in double transgenic offspring most likely is caused by lambda 2(315) produced within the thymus rather than by maternally derived IgG, lambda 2(315). Nevertheless, IgG, lambda 2(315) can cause deletion of CD4+CD8+ thymocytes when injected in large amounts intraperitoneally into either adult or neonatal TCR-transgenic mice. Deletion is evident 48 and 72 h after injection, but by day 7 the thymus has already regained its normal appearance. A serum concentration of several hundred microgram/ml is required for deletion to be observed. Therefore, the heterogeneous idiotypes of serum Ig are probably each of too low concentration to cause thymocyte deletion in normal animals.

Animals↗
PubMed1993

Anti-tumour activity of idiotype-specific, MHC-restricted Th1 and Th2 clones in vitro and in vivo.

Idiotypes (Id) can serve as individual markers on B cells; therefore, cytotoxic Id-specific T cells may play a significant role in immunological surveillance of Id+ B-cell tumours. We have investigated the anti-tumour activity of CD4+ BALB/c Th1 and Th2 clones which recognize a processed Id of the syngeneic lambda 2(315) L chain in the context of the class II MHC molecule I-Ed. Id-specific T cells and A20/46 B lymphoma cells transfected with the lambda 2(315) gene were injected s.c. into the same site of BALB/c mice (Winn assay). The results show that both Th1 and Th2 clones can protect against tumour development. The protection was Id-specific because T cells did not influence tumour development by an A20/46 B lymphoma cell line transfected with the pSV2neo expression vector alone. In vitro studies showed that the Th1 clones were cytotoxic to lambda 2(315)-transfected B lymphoma cells; by contrast, the Th2 clone was not cytotoxic in 51Cr-release assay even though the Th2 cells inhibited the growth of lambda 2(315) B lymphoma cells. The anti-lymphoma properties of both the Th1 and Th2 clones appear to involve as yet undefined cytotoxic and growth inhibiting molecules.

Animals↗
PubMed1993

T-cell receptor alpha haplotype influences V alpha epitope expression on both cortisone-resistant thymocytes and lymph node T cells.

We have previously described a mouse strain congenic for the T-cell receptor alpha chain locus (Tcra). The strain, B10.D2.C-Tcraa/Bo, carries the Tcraa haplotype of BALB/c instead of the Tcrab haplotype normally found in B10.D2. By comparing B10.D2.C-Tcraa and B10.D2 mice, we now show that the Tcra haplotype influences the frequencies of V alpha 8 epitope expression on T cells detected by the novel B21.14 monoclonal antibody (MoAb). This finding agrees well with our previous observation that Tcra haplotype influences the frequencies of expression of two other V alpha 8 epitopes, detected by the KT50 and KT65 MoAbs. The specificities of the three V alpha 8-specific MoAbs were compared by scatter diagram analysis of staining frequencies obtained in individual mice. The B21.14 and KT50 MoAbs appear to have very similar specificities; these two MoAbs stain slightly more alpha beta T cells than the KT65 MoAb. Investigations with another novel MoAb, the V alpha 2-specific B20.1, revealed that the Tcra haplotype also influences the frequency of V alpha 2 epitope expression. The effect of the Tcra haplotype on V alpha 2 epitope expression was evident not only among lymph node T cells but also among mature, cortisone-resistant thymocytes. Thus, the influence of the Tcra haplotype is imprinted already in the thymus. The most likely explanations for Tcra haplotype dependency of V alpha epitope expression are differing numbers of V alpha-gene segment subfamily members and/or allelic polymorphism. The significance of Tcra haplotype-dependent V alpha epitope expression is discussed.

Animals↗