Biomedical subjects

J Kappler

Publications and source records attributed to J Kappler.

At least 19 recordsLinked to original sources

PubMed1992

The effects of chronic infection with a superantigen-producing virus.

C3H/HeJ mice transmit a mouse mammary tumor virus from mother to pup in milk. The retrovirus infects mice shortly after birth and, when expressed in recipient mice, produces a V beta 14-specific superantigen. The consequences of such expression on V beta 14-bearing T cells are examined in this paper. Most cells bearing V beta 14 and either CD4 or CD8 are eliminated in the thymus. Some V beta 14-bearing cells escape to the periphery, however. Those bearing CD8 are unaffected by expression of the viral superantigen. The percentage of peripheral CD4+ T cells bearing V beta 14 drops with time after birth. In large part this seems to be due to the fact that many of these cells become anergic because of exposure to the viral superantigen. Unlike normal T cells, these anergic cells cannot undergo peripheral postthymic expansion. Consequently, they drop in percentage even during a time when their total numbers are constant.

Animals↗

PubMed1992

The open reading frames in the 3' long terminal repeats of several mouse mammary tumor virus integrants encode V beta 3-specific superantigens.

Mice expressing the minor lymphocyte stimulation antigens, Mls-1a, -2a, or -3a, singly on the B10.BR background have been generated. Mls phenotypes correlate with the integration of mouse mammary tumor viruses (MTV) in the mouse genome. The open reading frames within the 3' long terminal repeats of the integrated MTVs 1, 3, 6, and 13 encode V beta 3-specific superantigens. Sequence data for these viral superantigens is presented, indicating that it is the COOH-terminal portion of the viral superantigen that interacts with the T cell receptor V beta element.

Amino Acid Sequence↗

PubMed1992

Late-onset metachromatic leukodystrophy: molecular pathology in two siblings.

We report on a new allele at the arylsulfatase A (ARSA) locus causing late-onset metachromatic leukodystrophy (MLD). In that allele arginine84, a residue that is highly conserved in the arylsulfatase gene family, is replaced by glutamine. In contrast to alleles that cause early-onset MLD, the arginine84 to glutamine substitution is associated with some residual ARSA activity. A comparison of genotypes, ARSA activities, and clinical data on 4 individuals carrying the allele of 81 patients with MLD examined, further validates the concept that different degrees of residual ARSA activity are the basis of phenotypical variation in MLD.

Adolescent↗

PubMed1991

A method for production of antibodies to human T-cell receptor beta-chain variable regions.

Mouse T-cell hybridomas bearing human V beta elements were produced by transfection of human/mouse hybrid T-cell receptor beta-chain genes into a mouse T-cell hybridoma lacking an endogenous beta-chain gene. These hybridomas were entirely mouse in origin except for the human V beta region. These cells were used to immunize mice against human V beta elements. Mouse monoclonal antibodies have thus been generated against human V beta 13.1 and -13.2. We expect that the method outlined in this paper will be useful in the production of monoclonal antibodies specific for other human V beta or V alpha elements.

Animals↗

PubMed1991

Altered antigen receptor signaling in anergic T cells from self-tolerant T-cell receptor beta-chain transgenic mice.

T-cell tolerance to the minor lymphocyte-stimulating antigen Mls-1a in a T-cell receptor (TcR) V beta 8.1 transgenic line of mice is maintained by both clonal deletion and clonal anergy. Approximately 20-50% of peripheral CD4+ (but not CD8+) T cells isolated from these mice are anergic and fail to proliferate following TcR ligation. We have examined key events in T-cell signaling in peripheral T cells isolated from these mice. In this report, we show that the anergic CD4+ T cells did not mobilize calcium or express receptors for interleukin 2 (IL-2) following TcR ligation. However, the cells retained viability and functional potential because stimulation with phorbol 12-myristate 13-acetate and ionomycin bypassed the block in receptor-mediated signaling and induced IL-2 receptor expression and proliferation of the anergic cells.

Animals↗

PubMed1991

A maternally inherited superantigen encoded by a mammary tumour virus.

A collection of superantigens, molecules which in combination with class II major histocompatibility complex (MHC) engage T cells bearing particular V beta chains as part of their alpha beta receptors, have recently been described. The mouse self superantigen, Mls-1a, for example, in conjunction with many MHC class II proteins, engages mouse T cells bearing V beta 6, 7, 8.1 and 9, almost regardless of the sequences of the other variable components of the receptors on the T cells. Two types of superantigen have been identified so far: first, superantigens encoded in the mouse genome, such as Mls-1a; second, superantigens produced by bacteria, such as the staphylococcal enterotoxins. Although the latter type of superantigens are in many cases known to be proteins of about 220 amino acids, nothing is known about the structures of any of the superantigens encoded in mouse. Here we describe the properties of a new mouse superantigen. The antigen is maternally transmitted in milk and is probably encoded by a mammary tumour virus (MTV). Given the known genetic linkage between at least one of the mouse genomic superantigens and endogenous MTV integration sites, it is tempting to speculate that the superantigen described here and some of the endogenous mouse superantigens are encoded by MTVs.

Animals↗

PubMed1991

Molecular basis of different forms of metachromatic leukodystrophy.

BACKGROUND: Metachromatic leukodystrophy is an autosomal recessive inherited lysosomal storage disorder caused by a deficiency of arylsulfatase A. Three forms of the disease can be distinguished according to severity and the age at onset: late infantile (1 to 2 years), juvenile (3 to 16), and adult (greater than 16). METHODS AND RESULTS: To understand the molecular basis of the different forms of the disease, we analyzed arylsulfatase A alleles associated with metachromatic leukodystrophy. Two alleles (termed I and A) were identified and accounted for about half of all arylsulfatase A alleles among 68 patients with metachromatic leukodystrophy whom we examined. Sufficient information was available for 66 of the patients to allow classification of their disease. Of the six instances of homozygosity for allele I, all were associated with the late-infantile form of the disease; of the eight instances of homozygosity for allele A, five were associated with the adult form and three with the juvenile form. When both alleles were present, the juvenile form resulted (seven of seven instances). Heterozygosity for allele I (with the other allele unknown) is usually associated with late-infantile disease, and heterozygosity for allele A with a later onset of the disease. The clinical variability can be explained by the different levels of residual arylsulfatase A activity associated with these genotypes. CONCLUSIONS: Like many lysosomal storage disorders, metachromatic leukodystrophy shows clinical heterogeneity that seems to reflect genetic heterogeneity. One of the known alleles (allele I) is associated with earlier and more severe disease than the other (allele A).

Adolescent↗

PubMed1991

Production of prostaglandin E2 and prostacyclin by thymic nurse cells in culture.

To better define the thymic microenvironment, we have examined a specific population of thymic stromal cells, thymic nurse cells (TNC) for production of eicosanoids. TNC were prepared from BALB/c mice, cultured in complete medium, and culture supernatants were analyzed for the presence of various metabolites of arachidonic acid. Freshly isolated TNC produced large quantities of PGE2 and 6-keto PGF1 alpha (a stable metabolite of prostacyclin, PGI2). Both of these eicosanoids were produced continuously in culture, after an initial lag period of approximately 2 h. No significant production of the eicosanoids PGD2, thromboxane B2, or leukotrienes B4, C4/D4/E4 was seen in these cultures. Production of PGE2 and PGI2 by TNC was not stimulated by treatment with the calcium ionophore A23187, or by cell-cell interactions resulting from coculture of the TNC with free thymocytes. Eicosanoid production in these cultures was not due to production of these substances by cells likely to be present as contaminants, such as T rosettes or free thymocytes. These findings raise the possibility that PGE2 and/or PGI2 may provide signals to thymocytes at a specific developmental stage.

6-Ketoprostaglandin F1 alpha↗

PubMed1991

Genotype-phenotype relationship in various degrees of arylsulfatase A deficiency.

Arylsulfatase A (ASA) is a lysosomal enzyme that hydrolyzes sulfatide. Absence of ASA activity leads to metachromatic leukodystrophy (MLD). The clinical outcome resulting from ASA deficiency is highly variable with respect to age of onset and symptoms. So far the causes for the variability are poorly understood. We have studied the relationship between the ASA genotype and the clinical phenotype. Fibroblasts from a total of 34 subjects with low ASA activity were examined with immunoblotting, a sensitive ASA assay, and the sulfatide loading test in order to characterize low ASA activity further. By these methods, three different classes of ASA deficiency can be defined: homozygosity for the pseudodeficiency allele (ASAp), compound heterozygosity for the ASAp and MLD (ASA-) alleles, and ASA-/ASA- genotypes. These genotypes exhibit different levels of ASA residual activity. Only ASA-/ASA- genotypes are associated with MLD. For diagnostic purposes, however, the differentiation of the various ASA genotypes is essential.

Adolescent↗

PubMed1991

Low arylsulphatase A activity and choreoathetotic syndrome in three siblings: differentiation of pseudodeficiency from metachromatic leukodystrophy.

We report on a family with a sibship of three children for whom the diagnosis of "an unusual form of metachromatic leukodystrophy (MLD)" had been suggested earlier. The patients had choreiform movements and dystonic posturing accompanied by dysarthria since childhood. The availability of the polymerase chain reaction enabled us to show that the three siblings have a pseudodeficiency genotype (ASAp/ASAp). There was no abnormal sulphatiduria, and we propose that the neurological disease and low arylsulphatase A activity are unrelated to one another in this family. A diagnosis of MLD carries very serious implications, and we recommend that gene amplification by polymerase chain reaction and hybridization with allele-specific oligonucleotide probes should be used to corroborate the diagnosis, especially when there is no abnormal sulphatiduria and when metachromatic material cannot be demonstrated in a sural nerve biopsy.

Adolescent↗

PubMed1991

Analysis of class II MHC structure in thymic nurse cells.

During the course of thymocyte maturation, the processes of positive selection and tolerance induction are mediated by interactions between thymocyte T-cell receptors and MHC molecules on thymic stromal cells. The means by which these seemingly contrary processes can be mediated by interactions between the same molecules has long been a source of controversy. One idea which has been put forward is that the MHC molecules in different microenvironments of the thymus are not the same. We have tested this hypothesis by examining class II transcripts derived from thymic cortical epithelial cells known as thymic nurse cells, reasoning that alternative splicing of primary transcripts might give rise to a positively selecting MHC molecule. However, we found no evidence for alternative splicing of these transcripts. These results are presented and discussed with regard to implications for possible mechanisms of positive selection.

Amino Acid Sequence↗

PubMed1991

Molecular genetics of metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by the deficiency of arylsulfatase A (ASA). The ASA cDNA as well as the gene has been cloned. The gene is about 3 kb long and consists of 8 exons. The two most frequent alleles causing MLD have been characterized and the distribution of these alleles among patients with different clinical forms of MLD has revealed a simple genotype-phenotype correlation. Some individuals have low ASA activities but are healthy. This condition has been called ASA pseudodeficiency. These individuals are homozygous for the ASA pseudodeficiency allele which only encodes 5-10% of the ASA activity compared to the normal allele. The mutations in the PD allele have been characterized. Based on the knowledge of these mutations diagnostic assays have been developed to differentiate ASA deficiencies associated with PD or MLD.

Alleles↗

PubMed1991

Phenotypic consequences of low arylsulfatase A genotypes (ASAp/ASAp and ASA-/ASAp): does there exist an association with multiple sclerosis?

Arylsulfatase A (ASA) pseudodeficiency does per definitionem not lead to metachromatic leukodystrophy. It is conceivable, however, that it may contribute to the susceptibility for more common, multifactorial disorders of the nervous system. In order to examine whether there is an association with multiple sclerosis (MS), the most common demyelinating disease, we screened 160 MS patients for ASA activity and looked for pseudodeficiency genotypes using polymerase chain reaction. Four homozygotes for the ASA pseudodeficiency allele were found among the MS patients, but only one in the control sample. Further studies are necessary to validate whether ASA pseudodeficiency is associated with MS.

Alleles↗

PubMed1990

Superantigens interact with MHC class II molecules outside of the antigen groove.

Superantigens, including the staphylococcal enterotoxins and the minor lymphocyte stimulatory antigens, are highly potent immunostimulatory molecules, capable of activating virtually all T cells that express particular T cell receptor (TCR) variable regions. Superantigen stimulation of T lymphocytes depends on major histocompatibility complex (MHC) class II molecules, so there has been some debate as to whether superantigens interact with the antigen binding "groove" on class II complexes, just like conventional peptide antigens, or whether they bind elsewhere and serve as TCR coligands. We compared the presentation of peptide antigens and superantigens by a panel of mutant-presenting cell lines, each displaying an A kappa alpha chain with a single alanine replacement along the alpha helix proposed to form one face of the groove. The negligible effect of these 30 mutations on superantigen presentation, versus their drastic consequences for peptide presentation, prompts us to conclude that superantigens interact with MHC class II molecules outside the groove.

Amino Acid Sequence↗

PubMed1990

HLA-DR alleles differ in their ability to present staphylococcal enterotoxins to T cells.

Staphylococcal enterotoxins (SEs) have been shown to bind to major histocompatibility complex (MHC) class II proteins and stimulate T cells in a V beta-specific manner, and these V beta specificities for various SEs have been well documented in mice and humans. This study was undertaken in order to examine the ability of human class II molecules to present SEs to human and murine T cell hybridomas. Using a panel of transfectants expressing individual HLA class II antigens, we have shown that HLA-DR alleles differ in their ability to bind and present SEs. Since the HLA-DR proteins share a common alpha chain, these results indicate that the polymorphic beta chain plays an important role in SE binding and presentation to T cells. In addition, we have shown that human class II isotypes markedly differ in their ability to present SEs. The results of this study should provide information on the region of MHC class II molecules that interacts with foreign, and perhaps self, super-antigens.

Alleles↗

PubMed1990

Selective expansion of T cells expressing V beta 2 in toxic shock syndrome.

Infection with Staphylococcus aureus and the production of toxic shock syndrome toxin-1 (TSST-1) have been implicated in the pathogenesis of toxic shock syndrome. Previous in vitro studies have demonstrated that TSST-1 is a powerful but selective stimulator of human T cells, and that the majority of activated cells express the TCR V beta 2 gene segment. We therefore studied patients with toxic shock syndrome using a modification of the PCR to determine if expansion of V beta 2+ T cells is a marker of the in vivo disease process. Five of eight patients studied demonstrated markedly elevated levels of circulating V beta 2+ T cells, whereas none showed significantly elevated levels of T cells expressing other V beta gene segments. The results suggest that toxin-mediated T cell activation, which involves a large fraction of the human T cell repertoire, may be critical in the pathogenesis of this disease.

Antigens, CD↗

PubMed1990

Residues of the variable region of the T-cell-receptor beta-chain that interact with S. aureus toxin superantigens.

The alpha beta T-cell antigen receptor (TCR) recognizes antigenic peptides in the context of self major histocompatibility complex (MHC) molecules. The specificity of recognition of MHC plus antigen is generally determined by a combination of the variable elements of alpha- and beta-chains of the TCR. Several types of antigen, however, have been identified that, when bound to MHC molecules, stimulate T cells bearing particular variable-region beta-chain (V beta) elements irrespective of the other variable components of the TCR. These have been termed 'superantigens', and here we are concerned with one type of superantigen, the toxins produced by Staphylococcus aureus. T cells have been found that bear closely related members of the same V beta family but respond differently to S. aureus toxins; in particular, cells bearing the human V beta 13.2 element respond to toxin SEC2, whereas cells bearing human V beta 13.1 do not. We have now defined the residues of the V beta element responsible for this difference, and find that they reside in a region thought to lie on the side of the TCR molecule, away from the conventional antigen/MHC-binding site. The evolutionary conservation of this site may be due to its having an important role in some function of the TCR other than the binding of conventional antigen plus MHC.

Amino Acid Sequence↗

PubMed1990

The role of the T cell receptor in positive and negative selection of developing T cells.

Although many combinations of alpha beta T cell receptors are available to the T cells in any given organism, far fewer are actually used by mature T cells. The combinations used are limited by two selective processes, positive selection of T cells bearing receptors that will be useful to the host, and clonal elimination or inactivation of T cells bearing receptors that will be damaging to the host. The ways in which these two apparently contradictory processes occur, and the hypotheses that have been suggested to reconcile them, are discussed.

Animals↗