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Biomedical subjects

A Traunecker

Publications and source records attributed to A Traunecker.

At least 19 recordsLinked to original sources
PubMed1993

Constitutive expression of high levels of soluble mouse CD4 in transgenic mice does not interfere with their immune function.

Interactions of CD4 with the major histocompatibility complex (MHC) class II molecules are crucial during thymic development and subsequently for the function of single-positive CD4+CD8- T lymphocytes. Here, we have investigated the potential effects of soluble CD4 (sCD4) on the immune system. We generated two different transgenic mouse lines, which constitutively expressed either approximately 100 micrograms/ml of monovalent or approximately 20 micrograms/ml of decavalent mouse sCD4 molecules in their sera. Analysis of these mice revealed no differences compared to control littermates, e.g. the single-positive CD4+ cells developed normally and these cells responded to allogeneic and anti-CD3 antibody stimuli like the cells from control mice. Furthermore, the T helper cell function for antibody responses in vivo were not affected. Our data provide evidence that, in mouse, the CD4-MHC class II-interaction has very low affinity. Since sCD4 is considered to be a therapeutical agent for human immunodeficiency virus infection, these findings are not only of basic, but also of clinical interest.

Animals↗
PubMed1993

The T cell receptor alpha beta V-J shuffling shows lack of autonomy between the combining site and the constant domain of the receptor chains.

In order to assess the structural independence of the T cell receptor (TCR) combining site from the rest of the molecule we have generated two recombinant chains consisting of a TCR V-J alpha region linked to the C beta and a TCR V-J beta linked to the C alpha. If the V and C domains of the TCR form independent domains, as has been shown for the Ig molecules, we would expect to obtain a functional chimeric TCR. Interestingly, it was found that the shuffled molecules are produced intracellularly in T cell hybridomas, but are not expressed on the cell surface. To explain this failure of the shuffled molecules we propose that the TCR has a more compact structure, compared to the Ig, and that it is indispensable to keep a longitudinal inter-domain contact between the V-J and C portion to have a functional molecule.

Animals↗
PubMed1993

New simplified molecular design for functional T cell receptor.

We have produced a chimeric single-chain T cell receptor (TcR) that combines the specific antibody recognition function and TcR/CD3 signaling properties within the same polypeptide chain. This hybrid molecule consisted of a single-chain antibody combining site that was connected over a short spacer to the transmembrane and cytoplasmic region of CD3 zeta. When expressed on TcR- or TcR+ T cell hybridomas it could mediate recognition of relevant target cells and subsequent production of lymphokines; i.e. it could functionally replace the TcR/CD3 complex. Therefore, the single-chain TcR model presented here represents an interesting and useful means for the creation of T cells with new specificities.

Base Sequence↗
PubMed1992

Specific low-affinity recognition of major histocompatibility complex plus peptide by soluble T-cell receptor.

The T-cell receptor is necessary and sufficient for recognition of peptides presented by major histocompatibility complex molecules. Other adhesion molecules, like CD4 or CD8, play an auxiliary role in antigen recognition by T cells. Here we analyse T-cell receptor (TCR) binding using a soluble rather than a cell-bound receptor molecule. A TCR-immunoglobulin chimaera is constructed with the variable and the first constant regions of both the TCR alpha- and beta-chains linked to the immunoglobulin light-chain constant regions. This soluble TCR is expressed, assembled and secreted as an alpha beta heterodimer by a myeloma cell line transfected with the recombinant genes. Furthermore, the soluble TCR is biologically active: it specifically inhibits antigen-dependent activation of the relevant T-cell clones and thus discriminates between proper and irrelevant peptides presented by major histocompatibility complex molecules.

Animals↗
PubMed1992

Activated human T cells express a ligand for the human B cell-associated antigen CD40 which participates in T cell-dependent activation of B lymphocytes.

To identify the ligand for the B cell-associated antigen CD40, we constructed a chimeric immunoglobulin molecule where the extracellular portion of the CD40 protein replaced the normal immunoglobulin variable region. No binding was detected on resting peripheral blood T cells. However, following T cell activation with phorbol esters and ionomycin, the chimeric protein bound specifically to activated human T cells and precipitated a 35-kDa protein from such cells. The induction of the CD40 ligand was detectable on the cell surface after 1 h, with maximal expression after 8 h of stimulation. The T cells expressing CD40 ligand were predominantly CD4 positive, although a proportion of CD8-positive cells also expressed the protein. There was no particular correlation with CD45 phenotype. Finally, we found that soluble CD40 inhibited T-dependent B cell proliferation. The results are discussed in the context of cognate interactions between B and T cells.

Adult↗
PubMed1992

Janusin: new molecular design for bispecific reagents.

It is well established that soluble CD4 (sCD4) inhibits HIV infection in vitro, regardless of the virus strain or genetic variant. Most effective molecules, thus far, based on sCD4 are those in which CD4 is combined with immunoglobulin constant regions (CD4-IgG or CD4-IgM). Such molecules maintained HIV-gp120 specificity mediated by CD4 and also antibody effector functions such as complement activation, Fc receptor binding, long serum half-life or transport across the placental barrier. We have now developed sCD4 molecules which are even more potent anti-HIV reagents. These molecules are based on the principle of bispecific antibodies and they have properties capable of retargeting cytotoxic T lymphocytes onto HIV-infected cells and inducing efficient killing. CD4 combined with anti-human CD3 (FvCD3) single-chain combining site has been produced (CD4-FvCD3-JANUSIN). This molecule shows the expected biological activities, namely, binding to the 2 ligands, human CD3 and gp120, also efficiently retargeting CTLs of any specificity onto HIV-infected cells. In addition, several advantages over classical bispecific antibodies can be achieved: only one polypeptide, not a mixture containing the desired product, is produced, thus simplifying the purification process. In addition, Janusin designs do not contain the Ig Fc portion, which could mediate illegitimate retargeting of T-cells. In addition to CD4-FvCD3-JANUSIN, receptor-Fv, Fv-Fv or ligand-Fv Janusins can be produced.

Antibodies↗
PubMed1991

Development of lymphocytes in interleukin 7-transgenic mice.

We have developed and established mouse transgenic lines in which the mouse interleukin 7 gene was targeted for expression in the lymphoid cell compartment. Northern blot analysis indicate that the transgene is expressed in bone marrow (BM), spleen and thymus, but not in kidney, liver, brain or heart. Both the frequency and absolute numbers of B cell precursors and mature B lymphocytes are increased in the BM and spleen of the transgenic mice. Although there is no expansion of the pro-T lymphocyte population in the BM, the number of all major subsets of thymocytes and peripheral T lymphocytes is increased in the majority of the transgenic mice analyzed. The B and T cell lymphocytes in the transgenic mice are functionally competent. In contrast, the number of granulocytes and macrophages in the BM of transgenic mice is similar to that in control non-transgenic littermates. Our results indicate that interleukin 7 plays an important role in vivo in the development of B and T lymphocytes.

Animals↗
PubMed1991

Bispecific single chain molecules (Janusins) target cytotoxic lymphocytes on HIV infected cells.

The human immunodeficiency virus type 1 (HIV-1) uses cell surface CD4 as a receptor to infect susceptible cells. Therefore, different forms of soluble CD4 (sCD4) molecules have been developed recently for potential therapeutic purposes. Here we describe a novel design of sCD4 molecules which exploit cytotoxic T cells as their effector function. The principle of bispecific antibodies was exploited and further developed to create new bispecific reagents which could retarget cytotoxic T cells of any specificity and thus, induce killing of HIV-1 infected cells. The most advanced molecules, Janusins, contain in one polypeptide chain the first two N-terminal CD4 domains and single chain combining site against the human CD3 complex (FvCD3).

Amino Acid Sequence↗
PubMed1991

Surface expression of the beta T cell receptor (TCR) chain in the absence of other TCR or CD3 proteins on immature T cells.

T cell receptor (TCR) beta genes are rearranged prior to TCR alpha genes. A productively rearranged TCR beta gene suppresses further V beta gene rearrangement. Here we show that in beta TCR transgenic mice the TCR beta-chain can be expressed on the surface of immature CD4-8- thymocytes, but not on mature T cells, in the absence of any other known TCR chain and proteins of the CD3 complex. Analysis by NEPHGE and SDS-PAGE showed that at least some beta TCR exists on the surface as a large disulfide-linked complex with unknown acidic molecules. The introduction of the beta TCR gene into scid mice resulted in the expression of the beta TCR on the cell surface of thymocytes and induced the expression of CD4 and CD8 co-receptors as well as transcription of the alpha TCR locus.

Animals↗
PubMed1989

Production and secretion of recombinant soluble CD3 polypeptides by myeloma-derived transfectant clones.

Soluble forms of three human CD3 proteins have been produced by recombinant DNA techniques. The extracellular domain of CD3-gamma, -delta or -epsilon has been linked to the constant region of mouse immunoglobulin kappa light chain to form gamma-kappa, delta-kappa and epsilon-kappa chimaeric proteins. These are secreted by mouse myeloma-derived transfectant cell lines and are immunoprecipitable by CD3- or kappa-specific polyclonal antisera. Yields of 100-500 micrograms secreted recombinant proteins per litre of culture medium were obtained, which could be purified by anti-kappa affinity chromatography. The production of soluble CD3 illustrates the applicability of this technology to a loosely associated protein complex.

Antigens, Differentiation↗
PubMed1989

Highly efficient neutralization of HIV with recombinant CD4-immunoglobulin molecules.

The human immunodeficiency virus type 1 (HIV-1) exploits the cell surface CD4 molecule to initiate the infection which can lead, eventually, to acquired immunodeficiency syndrome (AIDS). The HIV-1 envelope protein, gp120, interacts specifically with CD4 and soluble CD4 molecules have been shown to inhibit HIV infectivity in vitro. Effective inhibition in vivo may, however, require more potent reagents. We describe here the generation of molecules which combine the specificity of CD4 and the effector functions of different immunoglobulin subclasses. Replacing the VH and CH1 domains of either mouse gamma 2a or mu heavy chains with the first two N-terminal domains of CD4 results in molecules that are secreted in the absence of any immunoglobulin light chains. We find that the pentameric CD4-IgM chimaera is at least 1,000-fold more active than its dimeric CD4-IgG counterpart in syncytium inhibition assays and that effector functions, such as the binding of Fc receptors and the first component of the complement cascade (Clq), are retained. Similar chimaeric molecules, combining CD4 with human IgG were recently described by Capon et al., but these included the CH1 domain and did not bind Clq. Deletion of the CH1 domain may allow the association and secretion of heavy chains in the absence of light chains, and we suggest that the basic design of our constructs may be generally and usefully applied.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Solubilizing the T-cell receptor--problems in solution.

Recombinant DNA technology has been central in answering some of the most important questions in immunology and has recently helped to define the complex of membrane associated proteins on T-cell surfaces responsible for antigen recognition. Here André Traunecker and colleagues describe attempts to facilitate the analysis of this complex using genetic engineering to produce solubilized T-cell receptor and associated molecules.

Animals↗
PubMed1988

Soluble CD4 molecules neutralize human immunodeficiency virus type 1.

Human immunodeficiency virus (HIV) infection can bring about total collapse of the immune system by infecting helper T lymphocytes which express CD4, the molecule which mediates interaction between the cell surface and viral envelope glycoprotein gp120 (refs 3-10). HIV apparently escapes the effects of neutralizing antibodies in vivo by generating new variants which must still interact with CD4 to maintain a cycle of infection. One route to block HIV infection, therefore, could use solubilized CD4 protein to inhibit attachment of the virus to its target cell. We have used recombinant DNA techniques to generate soluble forms of CD4, and show here that these are potent inhibitors of HIV infection in vitro.

Animals↗
PubMed1987

A new mouse TCR V gamma gene that shows remarkable evolutionary conservation.

We have identified a new mouse T-cell receptor V gamma gene segment, V gamma 4.4, which frequently undergoes rearrangements in AKR thymomas, and at a lower frequency in fetal thymocytes. V gamma 4.4 is the fourth and the most 5' V gene segment in the gamma 4 cluster, being 7.3 kb from V gamma 4.3. Surprisingly, V gamma 4.4 is more homologous to eight human V gamma genes than to the other mouse V gamma genes. It has only a 38% nucleotide and 21% amino acid sequence homology to the most homologous mouse V gamma gene (V gamma 4.1), whereas these homologies to the human V gamma 8 gene are as high as 68% and 48% respectively.

Animals↗
PubMed1986

Rearrangements of T cell receptor loci can be found only rarely in B lymphoid cells.

We have studied the rearrangement status of the T cell receptor genes in 64 B lymphoid cell lines, and we found that, unlike the immunoglobulin heavy chain genes in T lymphocytes, T cell receptor beta and related gamma chain genes are almost always in germ-line configuration in B lymphoid cells. The only exception was a myeloma MOPC511 (IgA, chi) which contained all T cell receptor genes, beta 1, beta 2, gamma 1, gamma 2, gamma 3 and alpha, in rearranged configuration in both homologous chromosomes. This exception supports the concept that all immunoglobulin and T cell receptor genes exploit the same recombinase to build their complete variable regions. Obviously, in MOPC511 cells the regulation, which confers the tissue specificity i.e. T vs. B lymphocytes, has failed.

B-Lymphocytes↗
PubMed1986

A novel approach for preparing anti-T cell receptor constant region antibodies.

To obtain antibodies against the individual chains of the T cell receptor (TCR) complex, we have produced chimeric proteins containing domains from immunoglobulin (Ig) and TCR polypeptide chains. Basically, the Ig light chains were used as carriers for the TCR constant (C) region domains. The exons which encode the main body of the C regions of the alpha, beta and the related gamma polypeptide chains were "engineered" into the intronic region between the rearranged Ig variable (V) region and C kappa region genes. All three chimeric genes were expressed in myeloma cells, and the proteins of expected apparent molecular weight were produced. Secreted proteins containing the C beta domain were purified from the culture supernatant by using anti-kappa antibody affinity columns, and two rabbits were then immunized with the purified protein. Both rabbits produced antibodies able to immunoprecipitate the heterodimeric TCR protein.

Animals↗