Transmembrane tumor necrosis factor is a potent inducer of colitis even in the absence of its secreted form

BACKGROUND & AIMS

Tumor necrosis factor (TNF) is cleaved proteolytically from a 26-kilodalton transmembrane precursor protein into secreted 17-kilodalton monomers. Transmembrane (tm) and secreted trimeric TNF are biologically active and may mediate distinct activities. We assessed the consequences of a complete inhibition of TNF processing on the course of colitis in recombination activating gene (RAG)2 -/- mice on transfer of CD4 CD45RB hi T cells.

METHODS

TNF -/- mice, transgenic for a noncleavable mutant TNF gene, were used as donors of CD4 T cells, and, on a RAG2 -/- background, also as recipients. Kinetics of disease development were compared in the absence of TNF, in the absence of secreted TNF, and in the presence of secreted and tmTNF. The analysis at the end of the observation period included the histopathologic assessment of the intestine and the localization of TNF and interferon gamma (IFNgamma)-expressing cells.

RESULTS

The complete prevention of TNF secretion in tmTNF transgenic RAG2 -/- mice neither prevented nor delayed disease induction by transferred transgenic for a noncleavable transmembrane mutant of mouse TNF (tmTNF tg) CD4 CD45RB hi T cells. tmTNF expression by transferred CD4 T cells, however, was not required for disease induction because severe colitis and weight loss also were observed in tmTNF RAG2 -/- recipients of TNF -/- CD4 CD45RB hi T cells. In the presence of tmTNF, the absence of secreted TNF did not affect frequency and distribution of TNF and interferon-gamma messenger RNA (mRNA)-expressing cells.

CONCLUSIONS

These results indicate that specific inhibitors of TNF processing are not appropriate for modulating the pro-inflammatory and disease-inducing effects of TNF in chronic inflammatory disorders of the intestine.

Virus-Induced Activation of Self-Specific TCRαβ CD8αα Intraepithelial Lymphocytes Does Not Abolish Their Self-Tolerance in the Intestine

TCRalphabeta CD8alphaalpha intestinal intraepithelial lymphocytes (IEL) represent an enigmatic subset of T cells, particularly, in regard to their potential functions and the apparent persistence of cells expressing self-specific TCR. We have used mice that are transgenic for the TCRalphabeta specific for the lymphocytic choriomeningitis virus (LCMV)-derived peptide gp33, and TCRalphabeta-transgenic mice that coexpress the gp33 Ag ubiquitously, to analyze the functional properties of TCRalphabeta CD8alphaalpha IEL in the presence, or absence, of their specific MHC-restricted Ag, and to assess the impact of molecular mimicry during a potent LCMV infection on potentially self-reactive TCRalphabeta CD8alphaalpha IEL. In this study, we show that the presence of the specific self-Ag results in reduced expression of IL-2, IFN-gamma, and IL-10 by resident TCRalphabeta CD8alphaalpha IEL while expression of mRNA for TGFbeta is not affected. We further demonstrate that despite their secluded location in the epithelium, TCRalphabeta CD8alphaalpha IEL are activated after infection of the intestinal mucosa with LCMV. Importantly, LCMV-induced activation of self-specific TCRalphabeta CD8alphaalpha IEL does not reverse their tolerance as no cytotoxic activity or up-regulated expression of proinflammatory cytokines is detected and no overt signs of autoimmunity are seen. Taken together, these results are in support of an immunoregulatory role for self-specific TCRalphabeta CD8alphaalpha in the intestinal mucosa and clearly speak against an involvement of this cell subset in inflammatory reactions and tissue destruction.

Cutting Edge: Stimulation with the Cognate Self-Antigen Induces Expression of the Ly49A Receptor on Self-Reactive T Cells Which Modulates Their Responsiveness

NK cell self-tolerance is maintained by inhibitory receptors specific for MHC class I molecules. Inhibitory NK receptors are also expressed on memory CD8 T cells but their biological relevance on T cells is unclear. In this study, we describe the expression of the Ly49A receptor on a subset of autoreactive T cells which persist in mice double-transgenic for the lymphocytic choriomeningitis virus-derived peptide gp33 and a TCRalphabeta specific for the gp33. No Ly49A-expressing cells are found in TCRalphabeta single-transgenic mice, indicating that the presence of the autoantigen is required for Ly49A induction. Direct evidence for an Ag-specific initiation of Ly49A expression has been obtained in vitro after stimulation of autoreactive TCRalphabeta T cells with the cognate self-Ag. This expression of Ly49A substantially reduces Ag-specific activation of autoreactive T cells. These findings thus suggest that autoantigen-specific induction of inhibitory NK cell receptors on T cells may contribute to peripheral self-tolerance.

[Evolution of the mitochondrial DNA cytochrome b gene in Tetraonidae birds]

Mitochondrial fragments containing the cytochrome b gene (1020 bp in size) of four bird species belonging to four genera of the family Tetraonidae (Tetrao parvirostris, Bonasa umbellus, Lagopus lagopus scoticus, and Falcipennis falcipennis) were directly sequenced. Of the 1020 nucleotide positions, 186 were variable and uniformly distributed over the gene and only 46 were parsimony informative. Most substitutions were synonymous. Replacement substitutions were detected for 15 out of 340 amino acid sites; only four replacements were parsimony informative. The greatest codon bias was found for leucine and serine. The C-T transitions and the G-C transversions were, respectively, the most common (60.7%) and the most rare (5.9%). The mutation frequencies were high at the third codon position (85.2%) and relatively low at the first and the second position. At the third codon position of the species examined, the guanine content was the lowest (3.3%) and the cytosine content was the highest (44.5%). Based on the cytochrome b gene sequences, phylogenetic relationships in the order Galliformes are inferred.

Molecular phylogeny of Palearctic-African Acrocephalus and Hippolais Warblers (Aves: Sylviidae)

Phylogenetic relationships of the reed warbler group (genera Acrocephalus, Hippolais, Chloropeta; Aves: Passeriformes) and their potential relatives were studied using nucleotide sequences (1 kb) of the mitochondrial cytochrome b gene. This species-rich but morphologically poorly differentiated group of insectivorous passerines is distributed in Eurasia, Africa, and Australasia. Intergeneric relationships were poorly resolved, but monophyly of the reed warbler group (including Chloropeta) versus other Sylviidae was strongly supported. A basal polytomy within the reed warbler group consists of seven branches and may indicate a rapid early radiation. In the genus Acrocephalus three major clades were identified, which corresponded to phenotypic groups characterized by body size and plumage patterns. However, current delimitation of some subgenera (Acrocephalus, Lusciniola, Bebrornis) is at variance with our phylogeny estimate, and appropriate revisions are proposed. The genus Hippolais, which may or may not be monophyletic, consisted of two well-supported clades of four species each. Some Acrocephalus taxa whose species status had been doubted (griseldis, tangorum, orientalis, australis) proved to be highly distinct genetically. Genetic distances between members of two pairs of allopatric Hippolais taxa (caligata/rama; opaca/elaeica) were as large or larger than between other closely related warbler species. Overall, cytochrome b sequences resolved phylogenetically young relationships quite well, whereas more ancient nodes remained poorly resolved.

Cytochrome b gene haplotypes characterize chromosomal lineages of anoa, the Sulawesi dwarf buffalo (Bovidae: Bubalus sp.)

Partial mitochondrial cytochrome b gene sequences reveal two deeply differentiated mtDNA lineages in anoa dwarf buffaloes (Bubalus depressicornis) from the studbook herd in European zoos. Three matrilinear lineages of lowland anoas (depressicornis type) contributed three rather similar sequence haplotypes, but one remarkably distinct haplotype was observed exclusively in mountain anoas (quarlesi type) descended from one founder female. The carriers of the distinctive mtDNA haplotype were also distinguished by several chromosomal and phenotypic peculiarities too. The differentiation between the mtDNA lineages of anoa approached or even surpassed the genetic divergence between some uncontested species of wild cattle. The depth of this haplotype divergence in anoas is discussed against the background of the phylogenetic age of these paleoendemic inhabitants of a predator-free island refugium, Sulawesi, who are among the most plesiomorphic living bovines. The studbook breeding of captive anoas as a safeguard against extinction might profit from such population genetic markers. These cytochrome b gene sequences were unable to resolve the phylogeny of nine bovine taxa robustly, except the divergence of Bubalus, Synceros, Bison, and Bos (sensu lato) genera.

Evolutionary history of New and Old World vultures inferred from nucleotide sequences of the mitochondrial cytochrome b gene

The phylogeny of 11 species of Old World vultures (Aves: Accipitriformes, Aegypiinae), three species of New World vultures (Cathartidae) and theri nearest relatives within and outside the order Accipitriformes was investigated based on 1026 nucleotides of the mitochondrial cytochrome b gene. The data support the contention that New World vultures are not birds of prey, but phylogenetic information was insufficient to identify whether they are closer to storks (Ciconiidae) or to Accipitriformes. Four species of Gyps are all closely related and probably speciated within the Pleistocene. Molecular data do not support the split of 'white-backed' vultures from Gyps in a separate genus Pseudogyps. The monotypic genera of large, heavy-billed vultures, Aegypius, Torgos, Trigonoceps and Sarcogyps, are of monophyletic origin. We propose to merge Torgos with Aegypius, but retain Trigonoceps and Sarcogyps as separate genera, Sarcogyps being clearly the most primitive of the four. All four, together with Gyps and Necrosyrtes, form a monophyletic subfamily or 'core group', to which the subfamily Aegypiinae should be restricted. This group shares a more recent common ancestor with several non-vulture genera of Accipitrids, among them Buteo, Aquila, Haliaeetus and Circaetus, than it does with the two aberrent vultures Gypaetus barbatus and Neophron percnopterus. The last two are much more primitive; they seem to be each other's sister species and are closer to Pernis than to other Accipitrids. We propose separating Gypaetus and Neophron in the subfamily Gypaetinae. If the cytochrome b gene tree accurately reflects vulture phylogeny, Old World vultures are polyphyletic with the Aegypius-Gyps clade having evolved convergently to the more ancient Gypaetus and Neophron vultures. Polyphyly of Old World vultures, although in conflict with the DNA-DNA hybridization phylogeny of Sibley & Ahlquist (1990), is well supported by molecular, karyotypic, morphological and other phenotypic evidence (behaviour, voice) indicating fundamental differences between the two evolutionary lines.

[Assessment of "coping with disease" in patients with amyotrophic lateral sclerosis (ALS): on the use of an interviewer assessment rating scale]

Theories on "Coping" try to explain which resources people use to master crises and conflict situations. Reactions to challenges of life are considered as "coping strategies". In psychosomatic research, the notion of "coping" serves to describe how patients can handle physical or mental illness. Myatrophic (or amyothrophic) lateral sclerosis (ALS) is a rare chronic progressive disease of the nervous system with a gradual loss of motor neurons, resulting in muscular atrophy, weakness and spasticity. Since the etiology is unknown and no curative treatment available, most patients die from respiratory failure within a few years. In a follow-up study on physical disability, medical care and social support in 21 patients with advanced ALS, we tried to address the question how patients get along with such a threatening condition. After semi-standardized clinical interviews with patients and close relatives, two investigators gave independent descriptions of reported or observed "coping strategies" (rated as "not at all-barely-possibly-probably-very probably present"). Considering 17 patients assessed by both raters, significant agreement (Kendall's W) was achieved in three patients only. A comparison of aggregated answers (chi 2-Test) revealed different response sets, since one rater tended to choose extreme scale points, while the other preferred undecided answers. Differences of mean scores were observed in 8 out of 21 items, while significant correlations between investigators were obtained in another 8, including, though, only 2 of those 5 items which both had rated as "probably present" in no less than 50% of the patient sample ("Dejection & Flight-Brooding-Keeping the Situation Open-Distraction-Self-Isolation").(ABSTRACT TRUNCATED AT 250 WORDS)

[Disability in everyday tasks and subjective status of patients with advanced amyotrophic lateral sclerosis]

Out of 49 former inpatients diagnosed as suffering from myatrophic lateral sclerosis, 21 with a median illness duration of 33 months and severe physical handicaps took part in follow-up examinations as outpatients (n = 8) or have been visited at home (n = 9) or in nursing institutions (n = 4) another 21 patients had already died from the disease). Investigations included medical history (course of illness), neurological and psychiatric examination and interviews with relatives. Measures of daily living handicaps, quality of medical care, density of social network and amount of social support were obtained. In 16 cases, patients and relatives have been able to answer rating scales concerning patient's physical complaints, present mood, depression and anxiety. According to independent, but corresponding judgements of patients (selfrating), relatives and investigators, three out of four patients suffered from moderate or severe reactive depression. The severity of mood disturbance depended on the degree of physical disability in basic daily functions, rated as "loss of autonomy", and on measures of social isolation (number of relatives available). Handicapped and lonely patients seemed unable to cope with their fate, even if regular care was provided. According to former reports, ALS patients have a reputation of heroic stoicism with a low frequency of depression. Our own findings, obtained in patients with advanced disease, do not support these observations. The medical care--e.g. prescription of specific medication, nursing care, physiotherapy, supply of auxiliary devices and aids, nutrition--could often be considerably improved. Special emphasis is given to the indication and appropriate timing for a gastric feeding tube resp. a percutaneous endoscopic gastrostomy (PEG). A second focus of the discussion is the urgent need for communication devices for paralysed speechless patients.