Structural mutations of C-domains in members of the Ig superfamily. Consequences for the interactions between the T cell antigen receptor and the zeta 2 homodimer

Several molecules belonging to the Ig superfamily are expressed together with noncovalently associated subunits. This applies for membrane-bound IgM and IgD, some of the FcR, and the Ti dimers of the TCR. The interactions between members of the Ig superfamily and their associated subunits are still not fully understood. We locate critical amino acid residues for TCR assembly in the Ti-alpha and -beta extracellular C-domains. A point mutation (phenylalanine195----valine) in a highly conserved residue in the Ti-alpha chain of the Jurkat variant J79 was identified by DNA sequencing. This mutation did not prevent cytoplasmic association of Ti alpha beta and CD3 gamma delta epsilon, but abolished binding of the zeta 2 homodimer to the rest of the TCR. The consequences of this mutation for TCR assembly were confirmed by transfection of a site-directed mutagenized Ti-alpha chain into a Ti-alpha-deficient Jurkat variant. Computer model analysis showed that the Ti-alpha phenylalanine195 directly contributed to the beta-sheet facing away from the Ti-beta chain, indicating that it could be directly involved in the interactions between one or more of the CD3 chains or the zeta 2 dimer. Site-directed mutagenesis of the corresponding residue in the Ti-beta chain demonstrated that a phenylalanine216----valine substitution had similar effects on TCR assembly as the Ti-alpha mutation, whereas a phenylalanine216----histidine substitution allowed TCR assembly and expression. Whether the consequences for TCR assembly of the Ti-alpha and -beta mutations were due to any direct effects on the interaction between zeta and the Ti alpha beta dimer or to indirect effects are discussed.

Structural mutations of C-domains in members of the Ig superfamily. Consequences for the interactions between the T cell antigen receptor and the zeta 2 homodimer

Several molecules belonging to the Ig superfamily are expressed together with noncovalently associated subunits. This applies for membrane-bound IgM and IgD, some of the FcR, and the Ti dimers of the TCR. The interactions between members of the Ig superfamily and their associated subunits are still not fully understood. We locate critical amino acid residues for TCR assembly in the Ti-alpha and -beta extracellular C-domains. A point mutation (phenylalanine195----valine) in a highly conserved residue in the Ti-alpha chain of the Jurkat variant J79 was identified by DNA sequencing. This mutation did not prevent cytoplasmic association of Ti alpha beta and CD3 gamma delta epsilon, but abolished binding of the zeta 2 homodimer to the rest of the TCR. The consequences of this mutation for TCR assembly were confirmed by transfection of a site-directed mutagenized Ti-alpha chain into a Ti-alpha-deficient Jurkat variant. Computer model analysis showed that the Ti-alpha phenylalanine195 directly contributed to the beta-sheet facing away from the Ti-beta chain, indicating that it could be directly involved in the interactions between one or more of the CD3 chains or the zeta 2 dimer. Site-directed mutagenesis of the corresponding residue in the Ti-beta chain demonstrated that a phenylalanine216----valine substitution had similar effects on TCR assembly as the Ti-alpha mutation, whereas a phenylalanine216----histidine substitution allowed TCR assembly and expression. Whether the consequences for TCR assembly of the Ti-alpha and -beta mutations were due to any direct effects on the interaction between zeta and the Ti alpha beta dimer or to indirect effects are discussed.

Systemic phospholipase A2 and cachectin levels in adult respiratory distress syndrome and multiple-organ failure

In this clinical study we have prospectively measured plasma phospholipase A2 (PLA2) activity and tumor necrosis factor (TNF) levels in ventilated intensive care unit (ICU) patients with (n = 9) and without (n = 12) evidence of respiratory distress syndrome (ARDS) and multiple-organ failure (MOF). The median peak TNF concentration in control patients was 40 ng/L (range less than 40-100 ng/L) and in ARDS patients 231 ng/L (range 100-2550 ng/L; p less than 0.001). All of the control patients were discharged alive from the ICU, whereas 6 of 9 ARDS patients died in the ICU. In 6 ARDS patients, it was possible to measure more than 4 consecutive plasma TNF levels. Of these 6 patients, the 3 with persistent elevations in systemic TNF above 230 ng/L succumbed (p less than 0.05, one-tailed). Patients with ARDS also had parallel elevations in plasma PLA2 activity above controls. These elevations were significant for arterial PLA2 activity but not for venous PLA2 activity. Our study suggests that serial measurement of plasma (arterial or venous) TNF levels may have (1) prognostic and (2) etiologic significance in ICU patients with ARDS and MOF.

Retinal toxicity in human immunodeficiency virus-infected children treated with 2',3'-dideoxyinosine

To assess the safety and antiretroviral activity of 2',3'-dideoxyinosine, we enrolled 43 children with symptomatic (Centers for Disease Control class P-2) human immunodeficiency virus infection in a Phase I-II study and monitored them prospectively for the development of ocular complications secondary to HIV infection or drug toxicity. Follow-up ranged from 12 to 103 weeks with a median follow-up of 71 weeks. Three of 43 children (7.0%) developed peripheral atrophy of the retinal pigment epithelium during treatment with 2',3'-dideoxyinosine. The two children with the most severe retinal atrophy were enrolled in the study at the highest dosage studied (540 mg/m2/day). In contrast to findings in children, no retinal atrophy in HIV-infected adults treated with 2',3'-dideoxyinosine has been evident to date.

Ocular complications of Stevens-Johnson syndrome and toxic epidermal necrolysis in patients with AIDS

Recent reports suggest that acquired immunodeficiency syndrome (AIDS) patients are at higher risk of developing mucocutaneous reactions such as toxic epidermal necrolysis and Stevens-Johnson syndrome (SJS). Resultant dry eye may be further exacerbated by human immunodeficiency virus (HIV) related lacrimal gland dysfunction and lead to a chronic keratoconjunctivitis. We report one patient with AIDS and toxic epidermal necrolysis and two patients with AIDS and SJS who developed severe dry eye misdiagnosed as infectious keratoconjunctivitis. Cicatrizing mucocutaneous reactions should be suspected in AIDS patients and the dry eye treated to control symptoms and prevent complications.

Molteno implants as a treatment for refractory glaucoma in black patients

Eighty-two black patients with refractory glaucoma were treated with a single-plate Molteno implant inserted in a single-stage procedure. A successful outcome (intraocular pressure less than or equal to 21 mm Hg with or without adjunctive medical therapy) was achieved in 72% of the patients with a mean follow-up of 30 months. Success was achieved in 23 (73%) of the 31 patients with open angle glaucoma, 20 (83%) of the 24 patients with either aphakic or pseudophakic glaucoma, 12 (67%) of the 18 patients with neovascular glaucoma, four (80%) of the five patients with uveitic glaucoma, and two (50%) of the four patients with congenital glaucoma. All but four patients required additional medical therapy. Visual acuities remained the same or improved in 21 (68%) of the 31 patients with open angle glaucoma, 11 (61%) of the 18 with neovascular glaucoma, 19 (79%) of the 24 patients with aphakic/pseudophakic glaucoma, three (75%) of the four patients with congenital glaucoma, and four (80%) of the five patients with uveitic glaucoma. Complications included hyphema (18%), "kissing" choroidal effusion (6%), blocked tube (8%), flat anterior chamber (12%), cataracts (5%), Tenon's cyst (encapsulated bleb) (17%), uveitis (7%), phthisis bulbi (5%), and erosion of the silicone tube (1%).

A canine model of paired graft thrombosis

A novel canine model for reliably producing graft thrombosis is described. Two unilateral aortoiliac bypasses are performed while preserving the integrity of the native vascular tree. These grafts are briefly mechanically occluded at the time of the initial operation, and they remain occluded postoperatively because flow is preferentially directed through the larger-caliber, thrombo-resistant native circulation. Percutaneous temporary intra-arterial balloon occlusion of the native vessels redirects flow into the occluded graft segments, which can be used in experimental protocols. This new model for studying graft thrombosis requires only a single, simple operative procedure, and easily allows secondary percutaneous graft manipulation.

A clinically applicable method for long-term salvage of postischemic skeletal muscle

The clinical significance and applicability of interventions aimed at reducing reperfusion injury in postischemic skeletal muscle remain unproven, since long-term muscle salvage has not been demonstrated by most treatment protocols that attenuate early reperfusion injury. We have shown that reperfusion of ischemic skeletal muscle results in an early and prolonged sequestration of white blood cells and activation of the alternative complement cascade. The purpose of this study was to determine if 40 minutes of reperfusion with blood depleted of white blood cells and complement proteins, followed by 2 days of normal perfusion, would reduce muscle necrosis after 5 hours of ischemia. The isolated paired canine gracilis muscle model was used. The treatment muscle was initially reperfused with arterial blood that had been spun, washed, passed through a leukocyte removal filter, and resuspended in hydroxyethyl starch (greater than 99.9% removal of white blood cells and the complement proteins factor B and C4). The contralateral control muscle was subjected to unaltered reperfusion. Blood flow (ml/min/100 gm) was measured by timed collection of gracilis venous blood. Myeloperoxidase activity (absorbance at 655 nm/min/mg tissue protein) in muscle biopsies was used to monitor white blood cell sequestration. After 48 hours of reperfusion in vivo, necrosis was quantified by nitroblue tetrazolium staining. Initial reperfusion with white blood cell and complement depleted blood significantly reduced muscle necrosis (53% +/- 3% vs 29% +/- 8%, p less than 0.0025, paired t test). Early blood flow was improved, (p = 0.0025, repeated measure-ANOVA), but subsequent white blood cell sequestration was not altered (p = 0.33, repeated measure-ANOVA). This suggests that a significant amount of white blood cell mediated injury occurs during the first 40 minutes of reperfusion. Preventing early complement activation and white blood cell mediated reperfusion injury is an intervention that is feasible during surgery and may result in clinically significant salvage of postischemic skeletal muscle.

Differential response to the herbicidal activity of delta-aminolevulinic acid in plants with high and low SOD activity

delta-aminolevulinic acid (ALA) is the obligatory precursor for tetrapyrroles and for chlorophylls in plants. Under illumination, these photosensitizers generate singlet oxygen, thus causing bleaching and death of treated tissues. We have examined whether superoxide is involved in the mode of action of ALA and whether SOD provides protection. Bean genotypes with similar carotenoid content but differing in SOD activity and cucumber seedlings were used throughout. Cucumber plants treated with 10 mM ethanolamine (EA) prior to ALA, had higher levels of chlorophyll fluorescence and lower values of electrolyte leakage than control. Bean cultivars with high SOD activity were considerably more tolerant to membrane damage caused by ALA than those with low SOD activity. SOD activity was greatly reduced in cucumber leaves treated with diethyldithiocarbamate (DDTC). Electrolyte leakage was markedly increased and chlorophyll fluorescence values were significantly lower in DDTC and ALA treated tissues as compared with those treated with ALA only. The results indicate that superoxide is involved in the toxicity caused by ALA and that, by breeding for high SOD activity, resistance to ALA can be achieved, thus allowing the use of ALA as a selective herbicide in the field.

Dormancy patterns in buried seeds of Datura ferox and D. stramonium

Seasonal changes in seed dormancy of Datura ferox L. and D. stramonium L. were studied during 2 years in seeds buried in the field and compared with changes in dormancy of dry-stored seeds. Dormancy levels were evaluated by measuring the germination of exhumed and dry-stored seeds under 32:27 °C (nondormant seeds) or 32:12 °C (relatively dormant seeds). Levels of relative or full dormancy did not change during 2 years of dry storage in either species. Seed burial at 20 cm accelerated after-ripening, and primary dormancy disappeared earlier than at 5 cm. However, burial depths greater than 10 cm prevented germination in situ. This inhibition was not due to smaller daily fluctuations of soil temperature with increasing depth, since seeds buried at 20 cm and kept at 32:12 °C also failed to germinate. Transferring seeds to shallower soil layers allowed their germination. Cyclic seasonal changes in dormancy were found in buried seeds of D. ferox but not in D. stramonium. In D. ferox, dormancy was alleviated during the winter and germinability was maximal in early spring; the increase in dormancy was preceded by high late spring – summer temperatures. In D. stramonium most seeds near the soil surface germinated in the field in a brief flush in early winter, at temperatures under which D. ferox did not germinate. Key words: Datura, germination, dormancy, buried seeds, temperature.

Transmembrane signalling via HLA-DR molecules on T cells from a Sezary T-cell leukaemia line

The human Sezary T-cell leukaemia line, HUT.78, represents a population of activated T cells, i.e. they are HLA-DR+ and IL-2R+. We have analysed the capacity of HUT.78 cells (1) to stimulate HLA-DR-specific T-cell lines or clones and (2) to be induced to synthesize IL-2 by anti-HLA-DR monoclonal antibodies. The results of our experiments show that HLA-DR molecules on HUT.78 cells can stimulate at least one HLA-DR-specific T-cell clone and can act as transmembrane signal transmitters.

Histopathologic study of the Molteno glaucoma implant in three patients

Three eyes with the Molteno glaucoma implant (one eye with epithelial downgrowth, one eye with iridocorneal endothelial syndrome, and one eye with aphakia and glaucoma) were enucleated two to six years after implantation. Histopathologic examinations disclosed no evidence of erosion of sclera or conjunctiva of the eye by the glaucoma implant device. In the outer layers of the bleb wall, few and mostly degenerated inflammatory cells were present, which represented a minimal inflammatory reaction. Scanning electron microscopy of the tubes in these three patients showed that the tube was intact, patent, and without signs of degradation. The tube entering into the anterior chamber caused no appreciable inflammation and maintained its patency even when downgrowth epithelial cells lined the anterior chamber. The Molteno plate induced little or no inflammatory reaction. Therefore, the Molteno glaucoma implant is a useful device for patients with high risk for failure after surgery for glaucoma.

Association of the human CD3-zeta chain with the alpha beta-T cell receptor/CD3 complex. Clues from a T cell variant with a mutated T cell receptor-alpha chain

The TCR for Ag, on the majority of human T cells, is a disulfide-linked heterodimer composed of TCR-alpha and -beta chains noncovalently associated with the monomorphic CD3 complex composed of the CD3-gamma, -delta, -epsilon, and -zeta chains. The interactions involved in the assembly of the various components of this multimeric protein complex are not fully understood. In this report, a variant of the human leukemic T cell line Jurkat that synthesized all of the known components of the TCR/CD3 complex but fails to express the TCR/CD3 complex at the cell surface is further characterized. This variant, J79, has a mutated TCR-alpha chain that does not affect the assembly of the pentameric form (TCR-alpha beta-CD3-gamma delta epsilon) of the TCR/CD3 complex but inhibits the assembly of the CD3-zeta homodimer with the rest of the complex (TCR-alpha beta-CD3-gamma delta epsilon----TCR-alpha beta-CD3-gamma delta epsilon zeta 2). Transfecting a wild-type TCR-alpha gene into J79 reconstituted expression of a complete functionally competent TCR/CD3 complex at the cell surface. The results indicate that the TCR-alpha chain plays a crucial role in the assembly of the CD3-zeta homodimer with the pentameric form of the TCR/CD3 complex.

Association of the human CD3-zeta chain with the alpha beta-T cell receptor/CD3 complex. Clues from a T cell variant with a mutated T cell receptor-alpha chain

The TCR for Ag, on the majority of human T cells, is a disulfide-linked heterodimer composed of TCR-alpha and -beta chains noncovalently associated with the monomorphic CD3 complex composed of the CD3-gamma, -delta, -epsilon, and -zeta chains. The interactions involved in the assembly of the various components of this multimeric protein complex are not fully understood. In this report, a variant of the human leukemic T cell line Jurkat that synthesized all of the known components of the TCR/CD3 complex but fails to express the TCR/CD3 complex at the cell surface is further characterized. This variant, J79, has a mutated TCR-alpha chain that does not affect the assembly of the pentameric form (TCR-alpha beta-CD3-gamma delta epsilon) of the TCR/CD3 complex but inhibits the assembly of the CD3-zeta homodimer with the rest of the complex (TCR-alpha beta-CD3-gamma delta epsilon----TCR-alpha beta-CD3-gamma delta epsilon zeta 2). Transfecting a wild-type TCR-alpha gene into J79 reconstituted expression of a complete functionally competent TCR/CD3 complex at the cell surface. The results indicate that the TCR-alpha chain plays a crucial role in the assembly of the CD3-zeta homodimer with the pentameric form of the TCR/CD3 complex.

The effect of systemic metronidazole after non-surgical treatment in moderate and advanced periodontitis in young adults

The effect of adjunctive systemic metronidazole was studied in patients with moderate and advanced periodontitis recalcitrant to comprehensive non-surgical treatment. The material originated from a randomly selected part of the population aged 31 to 40 years. After non-surgical treatment of 149 patients, 98 with persisting pathological pockets greater than or equal to 5 mm (52 men and 46 women) became the subjects for the study. Clinical parameters were registered and pocket contents subjected to laboratory analysis. The subjects were randomized into two groups according to a code list known only by the manufacturer and the statistician. The test group took three 400 mg metronidazole tablets daily for 1 week and the control group took placebo tablets. Reassessment 6 months later showed statistically significant clinical improvement, with a reduction in the number of sites greater than or equal to 5 mm in both test and control groups. Complete healing, with no pockets greater than or equal to 5 mm, was noted in 30% of the test group and 9% of the control group. The difference is statistically significant and shows the supplementary effect of adjunctive metronidazole in non-surgical treatment of moderate and advanced periodontitis.

Cellular and molecular characteristics of transformed T cells from an antigen-specific T-cell line

An antigen-specific T-cell line which transforms into T-lymphoma cells in vitro but apparently not in vivo is described. Membrane markers, tumorigenicity and T-cell receptor (TcR) V alpha and V beta-gene usage of the in vitro transformed T-cell line were analysed to investigate whether the transformation event was poly-, oligo-, or monoclonal. The results indicate that the T lymphoma has no chromosome abnormalities, contains no tumour-inducing virus, can induce clone-specific immunity, and is oligoclonal with respect to TcR V alpha and V beta expression. The nature of the transformation event and clinical application of vaccination against T lymphomas is discussed. In addition, the expressed TcR V alpha and V beta repertoire of Con A T blasts was apparently not affected by the Igh-l or the MHC haplotype, as investigated in Igh-l and MHC congeneic C57Bl mice.

Mouse cytolytic T cells reactive with rat islet tumour RIN 5AH-B cells

Insulin dependent (type 1) diabetes mellitus is considered to be an autoimmune disease characterized by a specific destruction of the insulin-producing pancreatic beta cells. We have explored the possibilities of raising T cells specific for putative pancreatic beta-cell autoantigens using a xenogeneic system. Mouse T cells were induced against the rat insulinoma cells RIN 5AH-B (RIN) and tested for their specific reactivity. No MHC class II-restricted beta-cell-specific helper T-cell reactivity could be detected within the bulk cultures as measured by proliferation, but a remarkably high cytotoxicity against the RIN cells was observed. The target antigen on the cell surface recognized by the generated cytotoxic T cells was shown to be the rat class I major histocompatibility antigen RT1g, and not a beta-cell or tumour cell-specific antigen associated with RIN cell MHC molecules. Our results demonstrate that it is feasible to evoke a xenogeneic T-cell response against the RIN cells. However, the mouse T cells recognize a dominant epitope present on the expressed rat class I major histocompatibility antigen RT1Ag and not a beta-cell-specific antigen. Hence, we conclude that it appears most unlikely that beta-cell-specific T cells can be raised in the xenogeneic system.

T cell activation. II. Activation of human T lymphoma cells by cross-linking of their MHC class I antigens

The present work demonstrates that antibody-induced cross-linking of MHC class I antigens on Jurkat T lymphoma cells leads to a rise in intracellular calcium (Cai2+) and, in the presence of phorbol ester (PMA), to IL-2 production and IL-2 receptor expression. The rise in Cai2+ exhibited a profile very different from that obtained after anti-CD3 antibody-induced activation suggesting that activation signals are transduced differently after binding of anti-CD3 antibody and class I cross-linking, respectively. However, when Cai2+ was examined in individual Jurkat cells by means of a digital image processing system no differences were observed after cross-linking with anti-CD3 and anti-MHC class I antibodies, respectively. Two CD3-negative mutant lymphoma lines were nearly totally refractory to class I cross-linking. Taken together our results may indicate the existence of a functional linkage between the T cell receptor complex and MHC class I molecules.

Potential antisecretory antidiarrheals. 2. Alpha 2-adrenergic 2-[(aryloxy)alkyl]imidazolines

Lofexidine, an alpha 2-agonist, has central hypotensive activity and peripheral intestinal antisecretory activity. Analogues were synthesized with increased polarity in an attempt to prevent penetration of the blood-brain barrier. The compounds were evaluated in the cholera toxin treated ligated jejunum of the rat and in the Ussing chamber with a rabbit ileum preparation. Active compounds were determined to be alpha 2-adrenergic agonists by yohimbine reversals of their Ussing chamber activities. The 2,6-dimethyl derivative of lofexidine, 4a, was as active as lofexidine in vivo, but derivatives with 2,6-substituents larger than ethyl were inactive. (Aryloxy)alkyl derivatives which have an imidazoline and a methyl or larger group as part of the alkyl exhibited the best antisecretory activity. Compounds with substituents in the para position of the phenyl ring were generally inactive. 3-Amino-2,6-dimethyl derivative 21 was twice as active as 4a. A 2-methyl substituent is required in the 3-amino series to retain good activity. 2-Methyl derivative 12a had activity comparable to that of 4a, while 6-methyl derivative 12f was inactive. Substituents on the 3-amino group did not affect the activity, but substituting a hydroxyl for the amino group produced an inactive compound. Replacing the phenyl moiety with a 4-indole resulted in retention of activity, but other heterocycles were inactive. Compound 12a was resolved and d isomer 32 was five times more potent than l isomer 33. The more active compounds in the rat cholera toxin assay (RCTA), when evaluated in the dog, exhibited antisecretory activity but also exhibited central nervous system (CNS) effects, sedation and ataxia, at 10 mg/kg, and in spontaneously hypertensive rats at 50 mg/kg. A measure of polarity, log P, was calculated for the (aryloxy)alkyl groups. Regression analysis showed no correlation of antisecretory ED50 to the calculated log P. The active compounds did not show a separation of the central CNS effects from the peripheral antisecretory activity by increasing the polarity.