Ochronotic arthropathy.
The authors report on 18 members of four generations of an alkaptonuric family. All three males in the third generation are clinically affected; two members of the family tree have undergone major joint surgery.
Alkaptonuria↗
Biomedical subjects
K Takacs
Publications and source records attributed to K Takacs.
Nonequivalent nuclear location of immunoglobulin alleles in B lymphocytes.
Individual B lymphocytes normally express immunoglobulin (Ig) proteins derived from single Ig heavy chain (H) and light chain (L) alleles. Allelic exclusion ensures monoallelic expression of Ig genes by each B cell to maintain single receptor specificity. Here we provide evidence that at later stages of B cell development, additional mechanisms may contribute to prioritizing expression of single IgH and IgL alleles. Fluorescent in situ hybridization analysis of primary splenic B cells isolated from normal and genetically manipulated mice showed that endogenous IgH, kappa and lambda alleles localized to different subnuclear environments after activation and had differential expression patterns. However, this differential recruitment and expression of Ig alleles was not typically seen among transformed B cell lines. These data raise the possibility that epigenetic factors help maintain the monoallelic expression of Ig.
Alleles↗
Critical role of costimulation in the activation of naive antigen-specific TCR transgenic CD8+ T cells in vitro.
The influence of costimulation on the activation of naive CD8+ T cells and thymocytes was studied in vitro using H-Y-specific TCR-transgenic mice and H-Y antigenic peptide. Using a variety of physiological APC types, the activation of naive CD8+ T cells depended strictly on costimulation, which could not be substituted by high epitope density. T cell activation is known to be regulated by the interactions between CD86/CD80 and CD28/CD152, although it remains unclear whether the B7 isoforms have distinct roles. Addition of soluble anti-CD86 Ab led to profound inhibition of T cell reactivity, further confirming the importance of costimulation in naive CD8+ T cell activation. Finally, TCR engagement in the absence of costimulation had no effect on the subsequent reactivity of peripheral naive transgenic CD8+ T cells, but induced nonresponsiveness in mature CD8+ transgenic thymocytes. Collectively, these results demonstrate the importance of costimulation for naive CD8+ T cell activation, suggest that CD80 and CD86 can mediate opposing effects, possibly due to differential interaction with CD152 and CD28, and indicate differences in the sensitivity of immature vs mature CD8+ T cells to the induction of nonresponsiveness following costimulation-deficient Ag presentation.
Abatacept↗
A role of Hsp60 in autoimmune diabetes: analysis in a transgenic model.
A pathogenic role for self-reactive cells against the stress protein Hsp60 has been proposed as one of the events leading to autoimmune destruction of pancreatic beta cells in the diabetes of nonobese diabetic (NOD) mice. To examine this hypothesis, we generated transgenic NOD mice carrying a murine Hsp60 transgene driven by the H-2E alpha class II promoter. This would be expected to direct expression of the transgene to antigen-presenting cells including those in the thymus and so induce immunological tolerance by deletion. Detailed analysis of Hsp60 expression revealed that the endogenous gene is itself expressed strongly in thymic medullary epithelium (and weakly in cortex) yet fails to induce tolerance. Transgenic mice with retargeted Hsp60 showed overexpression of the gene in thymic cortical epithelium and in bone marrow-derived cells. Analysis of spontaneous T-cell responses to a panel of self and heterologous Hsp60 antigens showed that tolerance to the protein had not been induced, although responses to an immunodominant 437-460 epitope implicated in disease were suppressed, probably indicating an epitope shift. This correlated with changes in disease susceptibility: insulitis in transgenic mice was substantially reduced so that pathology rarely progressed beyond periislet infiltration. This was reflected in a substantial reduction in hyperglycemia and disease. These data indicate that T cells specific for some epitopes of murine Hsp60 are likely to be involved in the islet-cell destruction that occurs in NOD mice.
Animals↗
Thymic repertoire selection by superantigens: presentation by human and mouse MHC molecules.
The initial report of T cell receptor (TCR) V beta-specific thymic selection in mice showed association with expression of H-2E molecules and affected V beta 17a T cells which were present in CD4+8+ double positive thymocytes but deleted from the CD4+ and CD8+ single positive populations. Similar deletions were subsequently reported for V beta 8.1+ and V beta 6+ T cells in Mls-1a mouse strains and for V beta 3+ T cells in Mls-2a/3a strains. The 'Mls antigens' are most effectively presented by H-2E molecules but certain alleles of H-2A molecules can also present these endogenous superantigens. Expression of Mls antigens can cause both V beta-specific thymic deletion and stimulation of peripheral T cells from Mls-negative strains. Another category of 'Mls-like' antigens cause only V beta-specific thymic deletion in H-2E+ strains, affecting V beta 5+ and V beta 11+ T cells. The non-MHC ligands responsible for each of these effects are superantigens analogous to the exogenous bacterial superantigens, which also show TCR V beta-specific stimulatory effects when presented by MHC class II positive antigen-presenting cells. The genes encoding endogenous superantigens in mice were shown to co-segregate with mouse mammary tumour virus integrations (Mtv) and to be the Mtv-LTR orf genes. In vitro translation of Mtv-LTR orf genes identified their products as type II integral membrane glycoproteins with the polymorphic C terminus outside the cell. These polymorphisms correlate with specificity for the different TCR V beta chains. Virtually all TCR V beta-specific negative selection in the mouse thymus can be accounted for by the expression of Mtv or MMTV (the infectious counterparts of Mtv proviral integrants) LTR-orf proteins, presented with H-2E or certain H-2A alleles. It is unlikely that TCR V beta-specific positive selection is due to endogenous superantigens since it does not segregate with Mtv genomes. In humans, HLA-DR molecules appear to be homologous with H-2E in mice whereas HLA-DQ are the homologues of H-2A. H-2E negative mice transgenic for HLA-DR alpha chain express a mouse/human heterodimeric molecule which presents Mtv superantigens causing TCR V beta-specific deletion. Such trans-species class II molecules are also effective in TCR V beta-specific positive selection of V beta 2+, V beta 6+ and V beta 10+ T cells. Taken together, these results show that human MHC class II molecules can interact with the murine T cell repertoire.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Transforming growth factor-alpha gene expression and action in the seminiferous tubule: peritubular cell-Sertoli cell interactions.
The local production and action of an epidermal growth factor (EGF)-like substance within the seminiferous tubule was investigated as a potential mediator of cell-cell interactions. Peritubular (myoid) and Sertoli cells were isolated and cultured under serum-free conditions. Proteins secreted by Sertoli and peritubular cells were found to contain a component that bound to the EGF receptor in a RRA. Separation of secreted proteins by reverse phase chromatography fractionated a protein that contained EGF bioactivity in its activity to stimulate growth of an EGF-dependent cell line. Biochemical properties examined for both Sertoli and peritubular cell EGF activities were similar with each other, but distinct from murine EGF. Northern blot analysis with an EGF cDNA probe did not detect EGF gene expression in peritubular, Sertoli, or germ cells. The possible production of an EGF-like substance such as transforming growth factor-alpha (TGF alpha) was investigated with a molecular probe to human TGF alpha. Both peritubular and Sertoli cells contained a 4.5-kilobase mRNA species that hybridized in a Northern blot analysis with a human TGF alpha cRNA probe. An immunoblot with a TGF alpha antisera confirmed the production of TGF alpha by the detection of a protein in both Sertoli and peritubular cell secreted proteins. TGF alpha gene expression was not detected in freshly isolated germ cells. Scatchard analysis revealed the presence of high affinity EGF receptors on peritubular cells and the absence of such receptors on Sertoli or germ cells. TGF alpha was found to stimulate peritubular cell proliferation, but had no effect on Sertoli cell growth. The effects of hormones and TGF alpha on Sertoli cell function and differentiation were assayed through an examination of transferrin production by Sertoli cells. TGF alpha had no direct effect on transferrin production or the ability of hormones to influence Sertoli cells. However, the presence of peritubular cells in coculture with Sertoli cells allowed TGF alpha to stimulate transferrin production. TGF alpha was also found to have relatively rapid effects on peritubular cell migration and the promotion of colony formation in culture. Cocultures of peritubular and Sertoli cells also responded to TGF alpha by the formation of large clusters of cells. Observations demonstrate the local production of TGF alpha by Sertoli and peritubular cells, and action of TGF alpha on peritubular cells and, potentially, Sertoli cells. The local production and action of TGF alpha may have a critical role as a paracrine/autocrine factor involved in the maintenance of testicular function.
Animals↗