Transgenic rearranged T cell receptor gene inhibits lymphadenopathy and accumulation of CD4-CD8-B220+ T cells in lpr/lpr mice.

The lpr gene in homozygous form induces development of CD4-CD8-B220+ T cells and lymphadenopathy in MRL and C57BL/6 mice. Although the propensity for excessive production of T cells is related to an intrinsic T cell defect, a thymus is also required because neonatal thymectomy eliminates lymphadenopathy. Recent evidence suggests that excessive production and release of autoreactive T cells from the thymus of lpr/lpr mice might lead to downregulation of CD4 and CD8 as a "fail safe" tolerance mechanism that occurs during late thymic or post-thymic development. To test this hypothesis, T cell receptor (TCR) transgenic mice that produce large numbers of immature thymocytes recognizing the H-2Db and male H-Y antigens were backcrossed with C57BL/6-lpr/lpr mice and MRL-lpr/lpr mice. It was predicted that Db male lpr/lpr mice would produce large numbers of autoreactive T cells during early thymic development that would lead to an accelerated lymphoproliferative disease. In contrast, Db female lpr/lpr mice would produce large numbers of Db H-Y-reactive T cells, but might not develop lymphadenopathy because the male H-Y antigen would not be present. Unexpectedly, there was complete elimination of lymphadenopathy in both male and female TCR transgenic lpr/lpr mice. The elimination of lymphadenopathy was not due to a failure of thymic maturation since the thymus of H-2Db female lpr/lpr mice contained nearly normal numbers of mature thymocytes. Elimination of lymphadenopathy was also not due to a lack of autoreactive T cells in the peripheral lymph nodes (LN) since there was an increased syngeneic mixed lymphocyte proliferative response of LNT cells from transgenic lpr/lpr compared with +/+ mice in vitro. Hypergammaglobulinemia and autoantibody production in the transgenic lpr/lpr was present at levels comparable with or higher than control nontransgenic lpr/lpr mice, suggesting a dissociation of autoantibody production from the lymphoproliferative disease in the TCR transgenic mice. Conversely, the development of lymphadenopathy and production of CD4-CD8-B220+ T cells appear to be intimately linked, as both were completely eliminated in T cells expressing the transgenic TCR. We propose that lymphoproliferation and production of CD4-CD8-6B2+ T cells in lpr/lpr mice is related to decreased expression of the TCR, and providing the T cells with a rearranged TCR transgene overcomes this defect.

Mice deficient for the myelin-associated glycoprotein show subtle abnormalities in myelin.

Using homologous recombination in embryonic stem cells, we have generated mice with a null mutation in the gene encoding the myelin-associated glycoprotein (MAG), a recognition molecule implicated in myelin formation. MAG-deficient mice appeared normal in motor coordination and spatial learning tasks. Normal myelin structure and nerve conduction in the PNS, with N-CAM overexpression at sites normally expressing MAG, suggested compensatory mechanisms. In the CNS, the onset of myelination was delayed, and subtle morphological abnormalities were detected in that the content of oligodendrocyte cytoplasm at the inner aspect of most myelin sheaths was reduced and that some axons were surrounded by two or more myelin sheaths. These observations suggest that MAG participates in the formation of the periaxonal cytoplasmic collar of oligodendrocytes and in the recognition between oligodendrocyte processes and axons.

Mouse teratocarcinoma and embryonic development. Two-dimensional protein patterns in nerve differentiation.

The transition in mouse teratocarcinomas of pluripotential stem cells to histogenetically determined ones of the neurogenic cell lineage was analysed at the total cellular protein level by two-dimensional gel electrophoresis. The change in morphology and function was found to be reflected by extensive shifts in the protein synthesis patterns. From a total of about 1000 resolved polypeptides that are synthesized in embryoid bodies of a multidifferentiating teratocarcinoma, about 12% (117 proteins) are not found or only present at a very much reduced level in two teratocarcinoma-derived neuroblastomas. On the other hand, the change in phenotype is accompanied by the de novo or greatly enhanced synthesis of another 69 proteins (about 7%) in the neurogenic tumors. In a screening for differentiation-specific proteins this set was compared with the protein synthesized in neural tissue of maturing brain and muscle tissue of developing limbs at three different postimplantation stages covering the onset of organogenesis. This comparison disclosed that a great portion of the differentiation-related proteins (26 proteins) are synthesized in both brain and muscle and are probably required by a differentiated cell in general like cytostructural proteins. Seventeen polypeptides, however, are synthesized in a cell type specific manner. In particular, 4 proteins that are synthesized in both neurogenic tumors and in brain but not in muscle tissue were tentatively called nerve-specific proteins (NSP) and are the most promising in further analyses of differentiation-specific proteins.

Mouse teratocarcinoma and embryonic development. Two-dimensional protein patterns in muscle differentiation.

Muscle cell differentiation was analysed by two-dimensional gel electrophoresis of newly synthesized proteins compared in two parallel systems: in mouse teratocarcinoma-derived tumors that became restricted in their developmental potential to the formation of muscle-like cells and in developing limbs of the early mouse fetus. Muscle cell differentiation in teratocarcinomas was found to be reflected by both a marked decrease in the rate of synthesis of about 12% (119 proteins) of the resolved polypeptides and a pronounced increase in the synthesis of another large set of proteins (83 proteins). The majority of the newly acquired proteins (46 proteins) were also detected in fetal brain and muscle tissue. These proteins are considered to be those which accompany differentiation in general, regardless of cell type, as e.g. ubiquitously occurring structural proteins. Their expression in the muscle cells of the tumors may reflect the normal aspect of this particular differentiation pathway. Five polypeptides were found to appear specifically in both myogenic tumors and developing limbs, but not during brain formation and were tentatively termed muscle-specific proteins (MSP). The identification of differentiation-related proteins in muscle development will allow us to analyse differentiation in early development in molecular terms.

Molecular signals for glial activation: pro- and anti-inflammatory cytokines in the injured brain.

Injury to the central nervous system leads to cellular changes not only in the affected neurons but also in adjacent glial cells. This neuroglial activation is a consistent feature in almost all forms of brain pathology and appears to reflect an evolutionarily-conserved program which plays an important role for the repair of the injured nervous system. Recent work in mice that are genetically-deficient for different cytokines (M-CSF, IL-6, TNF-alpha, TGF-beta 1) has begun to shed light on the molecular signals that regulate this cellular response. Here, the availability of cytokine-deficient animals with reduced or abolished neuroglial activation provides a direct approach to determine the function of the different components of the cellular response leading to repair and regeneration following neural trauma.

Affinity chromatography of nonhistone chromosomal proteins from lymphocytes on DNA-agarose columns.

A two step procedure is presented consisting of hydroxyapatite and DNA-agarose chromatography which allows the isolation of nonhistone chromosomal proteins with different affinities towards single stranded DNA. The application of this fractionation scheme to nonhistone chromosomal proteins from bovine lymphocytes is described.

Nerve-cell-specific proteins in teratocarcinoma-derived neuroblastomas and embryonic brain.

Neural differentiation was analyzed by two-dimensional gel electrophoresis in two parallel systems: in teratocarcinoma-derived tumors that became determined to the formation of nerve-like cells and in developing brain of the early mouse embryo. The comparative analysis revealed four putative nerve-specific proteins (NSP) with Mr of 29K, 26K, 20K, and 16K, each of which was synthesized in both neurogenic tumors and during brain development but not in muscle tissue of developing limbs nor in undifferentiated cells of a pluripotential teratocarcinoma. NSP 29 and NSP 20 were found to be transiently expressed early in brain development at gestation day 8.5. At this stage, NSP 26 was barely detectable, but was synthesized at higher rates in brain tissue of day-12 and day-15 embryos. NSP 16 was present in brain tissue at all analyzed developmental stages.

Specific binding of a nonhistone chromosomal protein from lymphocyte to DNA.

The isolation of a nonhistone chromosomal protein, NH30 000, from bovine lymphocytes by affinity chromatography on a DNA-agarose column is described. The procedure starts with nonhistone fraction NH4 obtained by hydroxyapatite chromatography as described previously [Blüthmann, H., Mrozek, S. & Gierer, A. (1975) Eur. J. Biochem. 58, 315-326]. Protein NH30 000 migrates as a single band with a molecular weight of 30 000 on sodium dodecylsulfate polyacrylamide gels. It contains, on a molar basis 25.3% acidic amino acids and 18.3% basic amino acid residues, 10.3% being lysine. End-group determination confirms that this protein is composed of one polypeptide chain with the NH2-terminal amino acid arginine. The binding of protein NH30 000 to native DNA of different molecular weights has been investigated by the nitrocellulose filter assay. The results suggest that in the presence of 0.2 M NaCl it binds about 30% of the DNA with binding sites every 1700 nucleotide pairs. Competition experiments show that protein NH30 000 exhibits a higher binding affinity for lymphocyte DNA in comparison to Escherichia coli DNA.

Changes in nonhistone chromosomal proteins in phytohemagglutininstimulated lymphocytes.

Stimulation of bovine lymphocytes with phytohemagglutinin results in quantitative as well as qualitative changes in the nonhistone chromosomal proteins. Analysis of these proteins by hydroxyapatite chromatography and sodium dodecylsulfate polyacrylamide gel electrophoresis shows not only a selective increase in the amount of some nonhistone proteins but also a decrease of other nonhistone protein bands. This observation is compatible with the view that nonhistone proteins have an inhibitory as well as an activating function at the genome level.

Non-histone chromosomal proteins. Their isolation and role in determining specificity of transcription in vitro.

We describe a method for fractionation of chromatin components by selective dissociation with salt in buffers containing 5 M urea in combination with cromatography on hydroxyapatite at 4 degrees C. This results in two histone and four non-histone fractions which are recovered in high yield and with minimal proteolytic contamination. Template capacity measurements of the isolated chromatins and pre-saturation competition hybridization experiments support the idea that a group of non-histone proteins activate the transcription of specific DNA sequences which were not transcribed from purified DNA to the same extent. In reconstitution experiments a non-histone protein fraction, NH4, prepared from lymphocyte chromatin by hydroxyapatite chromatography is shown to cause transcription in vitro of lymphocyte-specific RNA sequences. A subfraction with a molecular weight of 30 000 comprising 40% of the NH4 fraction protein is characteristic for this tissue and not found in liver chromatin.

Transgenic mice to study T-cell receptor gene regulation and repertoire formation.

Transgenic mice have been obtained with genes coding for an alpha beta T-cell receptor that recognizes the male-specific antigen H-Y in association with the Db class I major histocompatibility complex molecule. Most if not all of the T-cells express the beta chain encoded by the transgene and show allelic exclusion of endogenous beta genes. In contrast, the expression of the alpha transgene does not completely block rearrangement and formation of functional endogenous alpha genes. In H-2b transgenic female mice the transgenic T-cell receptor is functionally expressed on at least 30% of CD8+ peripheral T-lymphocytes as indicated by their ability to lyse male target cells. Also in transgenic H-2b male mice a large proportion of peripheral T-cells appear to express the transgenic receptor. However, these cells do not react with male target cells because they show only low level or no expression of CD8 cell interaction molecules. Tolerance is established in the male transgenic thymus through deletion of CD4+CD8+ immature thymocytes.

T-cell specific rearrangement of T-cell receptor beta transgenes in mice.

To study rearrangement of T cell receptor (TCR) genes, transgenic mice were generated with a TCR beta minilocus in germline configuration, containing three V beta, two D beta, fourteen J beta and two C beta gene segments and the TCR beta enhancer. Using the polymerase chain reaction as an analytical tool both partial DJ as well as complete VDJ rearrangements were seen, indicating that the minilocus contained all sequence elements required for rearrangment. Rearrangements of minilocus gene segments were restricted to T cells in the thymus and the periphery and did not occur in B cells. V beta 8.3 and V beta 5 sequences encoded by the minilocus were expressed on the surface of peripheral T cells at high frequencies. Transgenic mice with TCR minilocus genes will be a useful system to identify DNA sequence elements required for regulation of rearrangement in vivo.

Positive selection of antigen-specific T cells in thymus by restricting MHC molecules.

Thymus-derived lymphocytes (T cells) recognize antigen in the context of class I or class II molecules encoded by the major histocompatibility complex (MHC) by virtue of the heterodimeric alpha beta T-cell receptor (TCR). CD4 and CD8 molecules expressed on the surface of T cells bind to nonpolymorphic portions of class II and class I MHC molecules and assist the TCR in binding and possibly in signalling. The analysis of T-cell development in TCR transgenic mice has shown that the CD4/CD8 phenotype of T cells is determined by the interaction of the alpha beta TCR expressed on immature CD4+8+ thymocytes with polymorphic domains of thymic MHC molecules in the absence of nominal antigen. Here we provide direct evidence that positive selection of antigen-specific, class I MHC-restricted CD4-8+ T cells in the thymus requires the specific interaction of the alpha beta TCR with the restricting class I MHC molecule.

Tolerance in T-cell-receptor transgenic mice involves deletion of nonmature CD4+8+ thymocytes.

The mechanism of self-tolerance is studied in T-cell-receptor transgenic mice expressing a receptor in many of their T cells for the male (H-Y) antigen in the context of class I H-2Db MHC antigens. Autospecific T cells are deleted in male mice. The deletion affects only transgene-expressing cells with a relatively high surface-density of CD8 molecules, including nonmature CD4+ CD8+ thymocytes, and is not caused by anti-idiotype cells.

Specific antibody against a protein (p27) present in nonestablished fibroblasts. A putative microfilament-associated protein.

A specific polyclonal antibody has been raised against a basic cytoplasmic protein (p27) which is induced by serum in growth-arrested NIH 3T3 cells but is constitutively expressed in nonestablished fibroblasts. Immunoblotting analysis and [35S]methionine labeling show that p27 is absent in tissues and established cell lines of different types. However, it is present in fibroblasts from human, rat, mouse, and chicken origin and is highly conserved as determined by two-dimensional gel electrophoresis. Double immunofluorescence shows that p27 colocalizes with actin filaments. These observations would suggest that p27 is an actin-associated protein expressed in nonestablished fibroblasts.

Enzyme activity profiles in mouse teratocarcinomas. A quantitative ultramicroscale analysis.

Nine tumour lines with different developmental capacities were derived from spontaneous as well as from one induced teratocarcinoma: three teratocarcinoma-derived rhabdomyosarcomas TDR 602, TDR 694, and TDR 114; two teratocarcinoma-derived neuroblastomas TDN 2151 and TDN 2283; two teratocarcinoma-derived endodermal tumours TDE 274 and TDE 113; one multipotential teratocarcinoma OTT 2289, and one undifferentiated teratocarcinoma OTT 2158. Quantitative analyses of ten catabolic enzymes, i.e. alkaline and acid phosphatase, alpha- and beta-galactosidase, alpha- and beta-glucosidase, alpha-mannosidase, alpha-fucosidase, beta-glucuronidase, and hexosaminidase were carried out at the 20-cell level, and specific enzyme activity profiles were established for each of the tumour lines studied. These profiles may be used for the biochemical identification of a tumour type at the single cell level in addition to morphological and biological criteria.

Immunohistochemical localization of mouse testis-specific phosphoglycerate kinase (PGK-2) by monoclonal antibodies.

Monoclonal antibodies against mouse testis-specific phosphoglycerate kinase (PGK-2) were produced in order to determine immunohistochemically the onset of PGK-2 synthesis in the germinal epithelium of the mouse. PGK-2 was detected in testis sections in spermatids as early as stage 12 and in spermatozoa, but not in earlier stages of spermatogenesis nor in any somatic cells of the testis. During ontogeny, PGK-2 appears within the testis at day 30 post-partum, concomitant with spermatids entering the maturation phase. All three allelic isozymes PGK-2A, -2B, and -2C were detected equally by the monoclonal antibody in testis sections of several inbred mouse strains, each of which expresses a specific PGK-2 variant. Moreover, the monoclonal antibody against mouse PGK-2 reacted with heterologous sperm-specific PGK from rat, rabbit, and bull and, therefore, may serve as a useful immunochemical marker for mammalian spermatogenesis.

The generation of mature T cells requires interaction of the alpha beta T-cell receptor with major histocompatibility antigens.

THE T-cell repertoire within an individual is biased to recognize antigen in the context of self major histocompatibility complex (MHC) antigens. This is thought to depend on a process of positive selection during development. Support for this notion has recently been obtained in experiments using transgenic mice bearing genes for T-cell receptors (TCR) of defined specificity: T cells expressing the introduced genes form the main part of the mature T-cell population only in mice that express the appropriate MHC product. We have now extended these observations using TCR transgenic mice homozygous for the severe combined immunodeficiency (SCID) mutation which are defective in the rearrangement of both TCR and immunoglobulin genes. In this case mature thymocytes develop only in transgenic mice that express the MHC product which restricts the specificity of the transgenic TCR. This shows that the interaction of the alpha beta TCR with thymic MHC antigen is essential for the development of mature T cells. Furthermore, the peripheral lymph nodes of such mice are underdeveloped, suggesting that the peripheral expansion of mature T cells may require interactions with other lymphocytes expressing a range of receptors.

Development of myelin oligodendrocyte glycoprotein autoreactive transgenic B lymphocytes: receptor editing in vivo after encounter of a self-antigen distinct from myelin oligodendrocyte glycoprotein.

We explored mechanisms involved in B cell self-tolerance against brain autoantigens in a double-transgenic mouse model carrying the Ig H-chain (introduced by gene replacement) and/or the L-chain kappa (conventional transgenic) of the mAb 8.18C5, specific for the myelin oligodendrocyte glycoprotein (MOG). Previously, we demonstrated that B cells expressing solely the MOG-specific Ig H-chain differentiate without tolerogenic censure. We show now that double-transgenic (THkappa(mog)) B cells expressing transgenic Ig H- and L-chains are subjected to receptor editing. We show that in adult mice carrying both MOG-specific Ig H- and L-chains, the frequency of MOG-binding B cells is not higher than in mice expressing solely the transgenic Ig H-chain. In fact, in THkappa(mog) double-transgenic mice, the transgenic kappa(mog) L-chain was commonly replaced by endogenous L-chains, i.e., by receptor editing. In rearrangement-deficient RAG-2(-) mice, differentiation of THkappa(mog) B cells is blocked at an immature stage (defined by the B220(low)IgM(low)IgD(-) phenotype), reflecting interaction of the autoreactive B cells with a local self-determinant. The tolerogenic structure in the bone marrow is not classical MOG, because back-crossing THkappa(mog) mice into a MOG-deficient genetic background does not lead to an increase in the proportion of MOG-binding B cells. We propose that an as yet undefined self-Ag distinct from MOG cross-reacts with the THkappa(mog) B cell receptor and induces editing of the transgenic kappa(mog) L-chain in early immature B cells without affecting the pathogenic potential of the remaining MOG-specific B cells. This phenomenon represents a particular form of chain-specific split tolerance.