Effect of etanercept therapy on psoriasis symptoms in patients from Latin America, Central Europe, and Asia: a subset analysis of the PRISTINE trial

BACKGROUND

Psoriasis prevalence and characteristics in Asia, Central Europe, and Latin America have not been thoroughly investigated and there are no large trials for biologic treatments for patients from these regions. The goal of this analysis was to report clinical response to anti-tumor necrosis factor-alpha treatment in these patients.

METHODS

Patients from Argentina, Czech Republic, Hungary, Mexico, Taiwan, and Thailand (N=171) were included in this subset analysis of the PRISTINE trial. Patients with stable moderate-to-severe plaque psoriasis were blinded and randomized to receive etanercept 50 mg once weekly (QW) or biweekly (BIW) for 12 weeks, followed by 12 weeks of open-label QW treatment with etanercept 50 mg through week 24 (QW/QW vs. BIW/QW). Concomitant methotrexate (≤20 mg/week) and mild topical corticosteroids or other agents were permitted at the physician's discretion, in accordance with therapeutic practice.

RESULTS

As early as week 8, 26.7 % in the etanercept QW group and 44.0 % in the BIW group achieved Psoriasis Area and Severity Index (PASI) 75. At weeks 12 and 24, respectively, PASI 75 increased to 39.5 % and 62.8 % in the QW/QW group and 66.7 % and 83.3 % in the BIW/QW group. PASI 75 was significantly different between treatment groups from week 8 through the end of study (p<0.05). The Kaplan-Meier estimate of the proportions achieving PASI 75 in QW/QW and BIW/QW groups, respectively, was 27.4 % and 45.8 % through week 8; 41.9 % and 68.7 % through week 12; and 72.5 % and 95.2 % through week 24.

CONCLUSIONS

Treatment with etanercept 50 mg provided rapid relief of psoriasis symptoms in patients from Asia, Central Europe, and Latin America. A more rapid response was observed in patients who received BIW treatment for the first 12 weeks which was sustained after reducing to QW dosing for the subsequent 12 weeks. Response rates were similar to those observed in the overall PRISTINE population.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00663052 .

[Prenylation: from bacteria to eukaryotes]

For their protection from host cell immune defense, intracellular eukaryotic parasites developed a variety of mechanisms, including secretion systems III and IV which inject bacterial effectors directly into eukaryotic cells. These effectors may be posttranslational modified by host cell machinery and may function inside the host cell. Recently, to the list of possible posttranslational modifications of bacterial proteins the prenylation was added. In this work we describe current state of the knowledge about the prenylation of eukaryotic and prokaryotic proteins and its inhibitors. The bioinformatics analyses suggest possibility of prenylation for a number of Francisella genus proteins.

The role of European genetic admixture in the etiology of the insulin resistance syndrome in children: are the effects mediated by fat accumulation?

OBJECTIVES

To evaluate the contribution of European genetic admixture (EUADM) to insulin resistance syndrome (IRS) in a multiethnic sample of children age 7-12 years, and to explore whether body fat affects this relationship.

STUDY DESIGN

Anthropometric measurements and blood pressure were assessed in 243 children. After an overnight fast, an intravenous glucose tolerance test was conducted, and measures of fasting insulin/glucose, lipids, insulin sensitivity (SI), and acute insulin response to glucose (AIRg) were obtained. The proportion of EUADM was determined by maximum likelihood estimation using 140 ancestry informative markers. Subjects were stratified into tertiles according to the proportion of EUADM for analyses. Subjects were categorized as lean or obese using body fat percentage cutpoints (25% in boys, 30% in girls).

RESULTS

Among lean subjects (72%), the tertile representing the greatest proportion of EUADM was associated with higher SI (P<.001) and serum glucose (P<.05) and lower insulin (P<.05), AIRg (P<.001), high-density lipoprotein cholesterol (P=.05), and blood pressure (P<.05). However, among obese subjects, EUADM was associated only with SI (P<.05).

CONCLUSIONS

Our results suggest that population differences in IRS likely have a genetic component, but that the influence of genetic background may be masked by obesity.

Blockade of GpIIb/IIIa inhibits the release of vascular endothelial growth factor (VEGF) from tumor cell-activated platelets and experimental metastasis

Evidence that platelets play a role in tumor metastasis includes the observation of circulating tumor cell-platelet aggregates and the anti-metastatic effect of thrombocytopenia and anti-platelet drugs. Platelets have recently been shown to contain vascular endothelial growth factor (VEGF) which is released during clotting. We therefore studied the effects of (1) tumor cell-platelet adherence and tumor cell TF activity on platelet VEGF release; and (2) the effects of GpIIb/IIIa blockade on tumor cell-induced platelet VEGF release, tumor cell-induced thrombocytopenia and experimental metastasis. Adherent A375 human melanoma cells (TF+) and KG1 myeloid leukemia (TF-) cells were cultured in RPMI containing 10% fetal bovine serum. Platelet-rich plasma was obtained from normal citrated whole blood and the presence of VEGF (34 and 44 kDa isoforms) confirmed by immunoblotting. Platelet-rich plasma with or without anti-GpIIb/IIIa (Abciximab) was added to A375 monolayers and supernatant VEGF measured by ELISA. Tumor cell-induced platelet activation and release were determined by CD62P expression and serotonin release respectively. In vitro, tumor cell-platelet adherence was evaluated by flow cytometry. In vivo, thrombocytopenia and lung seeding were assessed 30 min and 18 days, respectively, after i.v. injection of Lewis Lung carcinoma (LL2) cells into control or murine 7E3 F(ab')(2) (6 mg/ kg) athymic rats. Maximal in vitro platelet activation (72% serotonin release) occurred 30 min after adding platelets to tumor cells. At this time, 87% of the A375 cells had adhered to platelets. Abciximab significantly (P<0.05) reduced platelet adherence to tumor cells as evidenced by flow cytometry. Incubation of A375 cells with platelets induced VEGF release in a time-dependent manner. This release was significantly inhibited by Abciximab (81% at 30 min; P<0.05). In the presence of fibrinogen and FII, VEGF release induced by A375 (TF+) cells was significantly higher than that induced by KG1 (TF-) cells (105.5+/-24 vs. 42+/-7 pg/ml; P<0.001). Omitting fibrinogen or FII from the reaction mixture markedly decreased VEGF release. In vivo, GpIIb/IIIa blockade with murine 7E3 F(ab')(2) reduced LL2 tumor cell-induced thrombocytopenia by 90% (P<0.001) and lung seeding by 82% (P<0.05). We conclude that TF-bearing tumor cells can activate platelets largely via thrombin generation, and that such activation is associated with release of VEGF. This may enhance metastasis, possibly by increasing extravasation at points of adhesion to vascular endothelium.

Bevacizumab immune complexes activate platelets and induce thrombosis in FCGR2A transgenic mice

BACKGROUND

Treatment with Bevacizumab has been associated with arterial thromboembolism in colorectal cancer patients. However, the mechanism of this remains poorly understood, and preclinical testing in mice failed to predict thrombosis.

OBJECTIVE

We investigated whether thrombosis might be the result of platelet activation mediated via the FcgammaRIIa (IgG) receptor - which is not present on mouse platelets - and aimed to identify the functional roles of heparin and platelet surface localization in Bev-induced FcgammaRIIa activation.

METHODS AND RESULTS

We found that Bev immune complexes (IC) activate platelets via FcgammaRIIa, and therefore attempted to reproduce this finding in vivo using FcgammaRIIa (hFcR) transgenic mice. Bev IC were shown to be thrombotic in hFcR mice in the presence of heparin. This activity required the heparin-binding domain of Bev's target, vascular endothelial growth factor (VEGF). Heparin promoted Bev IC deposition on to platelets in a mechanism similar to that observed with antibodies from patients with heparin-induced thrombocytopenia. When sub-active amounts of ADP or thrombin were used to prime platelets (simulating hypercoagulability in patients), Bev IC-induced dense granule release was significantly potentiated, and much lower (sub-therapeutic) heparin concentrations were sufficient for Bev IC-induced platelet aggregation.

CONCLUSIONS

The prevailing rationale for thrombosis in Bev therapy is that VEGF blockade leads to vascular inflammation and clotting. However, we conclude that Bev can induce platelet aggregation, degranulation and thrombosis through complex formation with VEGF and activation of the platelet FcgammaRIIa receptor, and that this provides a better explanation for the thrombotic events observed in vivo.

Bevacizumab immune complexes activate platelets and induce thrombosis in FCGR2A transgenic mice

BACKGROUND

Treatment with Bevacizumab has been associated with arterial thromboembolism in colorectal cancer patients. However, the mechanism of this remains poorly understood, and preclinical testing in mice failed to predict thrombosis.

OBJECTIVE

We investigated whether thrombosis might be the result of platelet activation mediated via the FcgammaRIIa (IgG) receptor - which is not present on mouse platelets - and aimed to identify the functional roles of heparin and platelet surface localization in Bev-induced FcgammaRIIa activation.

METHODS AND RESULTS

We found that Bev immune complexes (IC) activate platelets via FcgammaRIIa, and therefore attempted to reproduce this finding in vivo using FcgammaRIIa (hFcR) transgenic mice. Bev IC were shown to be thrombotic in hFcR mice in the presence of heparin. This activity required the heparin-binding domain of Bev's target, vascular endothelial growth factor (VEGF). Heparin promoted Bev IC deposition on to platelets in a mechanism similar to that observed with antibodies from patients with heparin-induced thrombocytopenia. When sub-active amounts of ADP or thrombin were used to prime platelets (simulating hypercoagulability in patients), Bev IC-induced dense granule release was significantly potentiated, and much lower (sub-therapeutic) heparin concentrations were sufficient for Bev IC-induced platelet aggregation.

CONCLUSIONS

The prevailing rationale for thrombosis in Bev therapy is that VEGF blockade leads to vascular inflammation and clotting. However, we conclude that Bev can induce platelet aggregation, degranulation and thrombosis through complex formation with VEGF and activation of the platelet FcgammaRIIa receptor, and that this provides a better explanation for the thrombotic events observed in vivo.

Phylogenetic characterization of a corrosive consortium isolated from a sour gas pipeline

Biocorrosion is a common problem in oil and gas industry facilities. Characterization of the microbial populations responsible for biocorrosion and the interactions between different microorganisms with metallic surfaces is required in order to implement efficient monitoring and control strategies. Denaturing gradient gel electrophoresis (DGGE) analysis was used to separate PCR products and sequence analysis revealed the bacterial composition of a consortium obtained from a sour gas pipeline in the Gulf of Mexico. Only one species of sulfate-reducing bacteria (SRB) was detected in this consortium. The rest of the population consisted of enteric bacteria with different characteristics and metabolic capabilities potentially related to biocorrosion. Therefore, several types of bacteria may be involved in biocorrosion arising from natural biofilms that develop in industrial facilities. The low abundance of the detected SRB was evidenced by environmental scanning electron microscopy (ESEM). In addition, the localized corrosion of pipeline steel in the presence of the consortium was clearly observed by ESEM after removing the adhered bacteria.

Antimetastatic effect of tinzaparin, a low-molecular-weight heparin

The importance of coagulation activation in cancer patients is suggested by the clinical finding of hypercoagulability, experimental enhancement of metastasis and angiogenesis by coagulation factors such as tissue factor (TF) and thrombin and the possible antitumor effects of anticoagulant agents. Tinzaparin is a low-molecular-weight heparin (LMWH) with a relatively high molecular weight distribution and high sulfate to carboxylate ratio. In addition to its ability to inhibit thrombin and factor Xa, tinzaparin is particularly effective at releasing endothelial tissue factor pathway inhibitor (TFPI), the natural inhibitor of both procoagulant and non-coagulant effects of TF. The present study was undertaken to investigate the effect of tinzaparin on lung metastasis using a B16 melanoma model in experimental mice. Tinzaparin's anticoagulant effect in mice and its ability to release TFPI from human endothelial cells at various time points were demonstrated. Subcutaneous (s.c.) injection of tinzaparin (10 mg kg-1) 4 h before intravenous administration of melanoma cells (2.0 x 105) markedly (89%) reduced lung tumor formation (3 +/- 2) compared with controls (31 +/- 23; P < 0.001). In a second group of animals, tinzaparin (10 mg kg-1, s.c.) administered daily for 14 days following the initial (pretumor cell) dose, before assessment of lung seeding, reduced tumor formation by 96% (P < 0.001). No bleeding problems were observed in any of the tinzaparin-treated animals, despite a 4-fold prolongation of the whole blood clotting time after a single s.c. dose of tinzaparin (10 mg kg-1). Administration of tumor cells (2 x 106) caused a rapid and significant fall in platelet count 15 min after injection (a sensitive marker of intravascular coagulation) in controls (939 +/- 37 vs. 498 +/- 94 x 106 mL-1, P < 0.01), but this was prevented by tinzaparin treatment (921 +/- 104 x 106 mL-1). These data provide further experimental evidence to support the potential for LMWH as antimetastatic agents.

Platelet-CD40 ligand interaction with melanoma cell and monocyte CD40 enhances cellular procoagulant activity

Platelet-tumor cell interactions are believed to be important in tumor metastasis. Tumor cell tissue factor (TF) expression enhances metastasis and angiogenesis, and is primarily responsible for tumor-induced thrombin generation and the formation of tumor cell-platelet aggregates. Activated platelets express and release CD40 ligand (CD40L), which induces endothelial TF expression by ligation to CD40. We investigated the effect of platelet-derived CD40L on the TF activity of human CD40-positive melanoma cells and monocytes by incubating supernatants from activated or resting platelets with tumor cells or monocytes, and by bringing resting or activated platelets into close apposition with tumor cell monolayers. CD40L was present on the surface of activated (but not resting) platelets and was also released following platelet activation. Both recombinant soluble CD40L (rsCD40L) and activated platelet supernatants increased procoagulant activity (PCA) and TF antigen in tumor cells and monocytes. The increase in TF activity induced by both rsCD40L and activated platelet supernatants was inhibited by anti-CD40L antibody. Furthermore, contact of activated platelets with tumor cells increased cellular PCA, and this effect was also inhibited by anti-CD40L. In malignancy, the increase in cellular TF activity via CD40 (tumor cell)-CD40L (platelet) interaction may possibly enhance intravascular coagulation and hematogenous metastasis.

Purification and properties of human melanoma cell tissue factor

Tissue factor (TF) is a transmembrane glycoprotein that acts as a receptor for nonactivated and activated factor VII (FVII) and triggers the coagulation cascade. TF plays an important role in hemostasis, but may also have noncoagulation functions in vascular development, angiogenesis, and tumor cell metastasis. In tumor cells, analysis of the role of TF has been hampered by the lack of purified TF. In this study, TF antigen was identified on human A375 malignant melanoma cells using flow cytometry. We further purified TF apoprotein 2,000-fold to homogeneity from A375 melanoma cells using immunoaffinity chromatography. On SDS-polyacrylamide gel electrophoresis under reduction, purified TF apoprotein gave two major protein bands corresponding to molecular weights of 53 and 34 to 36 KD. The identity of these forms of TF was confirmed by Western blotting using a polyclonal antibody against human brain TF. Under reduction, the TF antibody bound with a monomeric form of TF (53 KD), and without reduction, to several forms of TF (34 to 128 KD). Preliminary carbohydrate analysis suggested that TF is a glycoprotein and contains about 22% total carbohydrates. The coagulant activity of the purified apoprotein was reconstituted by the addition of phospholipids. The effects of varying concentrations (0 to 8 microg) of polyclonal antibodies to TF and FVII on TF procoagulant activity were studied. Both antibodies inhibited more than 70% of the procoagulant activity of TF in an FX activation assay. The complex formation between purified TF apoprotein and FVIIa was demonstrated by using an enzyme-linked immunosorbent assay. TF formed a complex with FVIIa in a concentration-dependent and saturable manner. We conclude that in human melanoma cells, TF occurs in monomeric and heterodimeric forms and appears to have similar properties as reported for TF from other sources.

Risk screening in a medicare/medicaid population administrative data versus self report

OBJECTIVE

To compare the abilities of two validated indices, one survey-based and the other database-derived, to prospectively identify high-cost, dual-eligible Medicare/Medicaid members.

DESIGN

A longitudinal cohort study.

SETTING

A Medicaid health maintenance organization in Philadelphia, Pa.

PARTICIPANTS

HMO enrollees (N = 558) 65 years and older eligible for both Medicare and Medicaid.

MEASUREMENTS AND MAIN RESULTS

Two hundred ninety six patients responded to a survey containing the Probability of Repeat Admission Questionnaire (Pra) between October and November 1998. Using readily available administrative data, we created an administrative proxy for the Pra. Choosing a cut point of 0.40 for both indices maximized sensitivity at 55% for the administrative proxy and 50% for the survey Pra. This classification yielded 103 high-risk patients by administrative proxy and 73 by survey Pra. High-cost patients averaged at least 2.3 times the resource utilization during the 6-month follow-up. Correlation between the two scores was 0.53, and the scales disagreed on high-cost risk in 78 patients (54 high-cost by administrative proxy only, and 24 high-cost by survey Pra only). These two discordant groups utilized intermediate levels of resources, $2,171 and $2,794, that were not statistically significantly different between the two groups (probability > chi2 =.66). Receiver operating characteristic curve areas (0.68 for survey Pra and administrative proxy for respondents, and 0.67 by administrative proxy for nonrespondents) revealed similar overall discriminative abilities for the two instruments for costs.

CONCLUSIONS

The Medicaid/Medicare dual-eligible population responded to the survey Pra at a rate of 53%, limiting its practical utility as a screening instrument. Using a cut point of 0.40, the administrative proxy performed as well as the survey Pra in this population and was equally applicable to nonrespondents. The time lag inherent in database screening limits its applicability for new patients, but combining database-driven and survey-based approaches holds promise for targeting patients who might benefit from case management intervention.

Hemoglobin enhances tissue factor expression on human malignant cells

Tissue Factor (TF) is a transmembrane glycoprotein that complexes with factor VII/activated factor VII to initiate blood coagulation. TF may be expressed on the surface of various cells including monocytes and endothelial cells. Over-expression of TF in human tumor cell lines promotes metastasis. We recently showed that hemoglobin (Hb) forms a specific complex with TF purified from human malignant melanoma cells and enhances its procoagulant activity (PCA). To further study this interaction, we examined the effect of Hb on the expression of TF on human malignant (TF+) cells and KG1 myeloid leukemia (TF-) cells. Human melanoma A375 and J82 bladder carcinoma cells, which express TF at moderate and relatively high levels, respectively, were incubated with varying concentrations (0-1.5 mg/ml) of Hb. After washing, cells were analyzed for Hb binding and TF expression using flow cytometry and confocal microscopy. Hb bound to the cells in a concentration-dependent manner, and increased both TF expression and PCA. The human A375 malignant melanoma cells incubated with Hb (1 mg/ml) expressed up to six times more TF antigen than cells without Hb. This increase in TF expression and PCA of intact cells incubated with Hb was significantly inhibited by cycloheximide at a concentration of 10 microg/ml (P < 0.01). An increase in total cellular TF antigen content was demonstrated by specific immunoassay. In contrast, Hb (5 mg/ml) did not induce TF expression and PCA on KG1 cells as determined by flow cytometry and TF (FXAA) activity. We conclude that Hb specifically binds to TF-bearing malignant cells and increases their PCA. This effect seems to be at least partly due to de novo synthesis of TF and increased surface expression. However, the exact mechanism by which Hb binds and upregulates TF expression remains to be determined.

Soluble fibrin augments platelet/tumor cell adherence in vitro and in vivo, and enhances experimental metastasis

There is considerable evidence for a relationship between hemostasis and malignancy. Since platelet adhesion to tumor cells has been implicated in the metastatic process and plasma levels of fibrinogen (Fg) and soluble fibrin (sFn) monomer are increased in cancer, we hypothesized that these molecules might enhance tumor-platelet interaction. We therefore studied binding of sFn monomer to tumor cells in a static microplate adhesion assay and determined the effect of pre-treating tumor cells with sFn on tumor cell-induced thrombocytopenia and experimental metastasis. Soluble fibrin (produced by adding thrombin to FXIII- and plasminogen-free Fg in the presence of Gly-Pro-Arg-Pro-amide (GPRP-NH2) significantly increased platelet adherence to tumor cells. This effect was primarily mediated by the integrins alphaIIb beta3 on the platelet and CD 54 (ICAM-1) on the tumor cells. Platelets adhered to untreated A375 cells (28 +/- 8 platelets/tumor cell) and this was not significantly affected by pre-treatment of the tumor cells with fibrinogen or GPRP-NH2. Although thrombin treatment increased adherence, pre-incubation of the tumor cells with sFn resulted in a further increase in platelet binding to tumor cells. In contrast to untreated tumor cells, intravenous injection of sFn-treated A 375 cells reduced the platelet count in anticoagulated mice, supporting the in vitro finding that sFn enhanced tumor cell-platelet adherence. In a more aggressive model of experimental metastasis, treating tumor cells with sFn enhanced lung seeding by 65% compared to untreated cells. Extrapolation of our data to the clinical situation suggests that coagulation activation, and subsequent increase in circulating Fn monomer, may enhance platelet adhesion to circulating tumor cells and thereby facilitate metastatic spread.

[Severe apnea: an early sign of Pneumocystis carinii pneumonia in an HIV-negative infant]

A few reports in the medical literature suggest an association between Pneumocystis caring and apnea in small infants. This patient, a 1 month 20 days old, HIV negative, infant girl weighing 2,000 grams was admitted to hospital after presenting a severe episode of apnea with cyanosis and bradycardia. She progressively developed bronchopneumonia by P. carinii that required prolonged mechanical ventilation with high ventilatory parameters. The clinical course of this patient illustrates that apnea can be an early sign of P. carinii infection in small infants. Early diagnosis and specific therapy might prevent morbidity and mortality and also decrease the length of hospitalization.

Pentoxifylline inhibits hypoxia-induced upregulation of tumor cell tissue factor and vascular endothelial growth factor

Tissue factor (TF), the membrane glycoprotein that initiates blood coagulation, is constitutively expressed by many tumor cells and is implicated in peri-tumor fibrin deposition and hypercoagulability in cancer. Upregulation of tumor TF correlates with enhanced metastatic potential. Furthermore, TF has been colocalized with VEGF in breast cancer, specially at sites of early angiogenesis. There are no data on the effect of hypoxia on tumor cell TF expression. Since hypoxia is known to stimulate VEGF production, we studied whether this also induces tumor cell TF expression. Confluent monolayers of A375 melanoma, MCF-7 breast carcinoma and A549 lung carcinoma were cultured in either 95% air, 5% CO2 (normoxic) or 95% N2, 5% CO2 (hypoxic; 25-30 mmHg) for 24 h. Procoagulant activity (PCA) was measured by amidolytic and clotting assays, surface TF antigen by flow cytometry, early apoptosis by annexin V binding and VEGF levels in culture supernatants by ELISA. Hypoxia significantly increased tumor cell PCA in all three cell lines tested and TF antigen on A375 cells was increased four-fold (P <0.05). Pentoxifylline (PTX), a methylxanthine derivative, significantly inhibited the hypoxia-induced increase in PCA as well as VEGF release in all three cell lines tested. In A375 cells, PTX significantly inhibited TF antigen expression by both normoxic and hypoxic cells. Hypoxia induced a slight (5%) but not significant, increase in early apoptosis. Intravenous injection of hypoxic A375 cells into nude rats produced more pronounced thrombocytopenia (n = 5, P <0.01) and more lung metastases (n = 3, P <0.05) compared to normoxic cells. We conclude that hypoxia increases TF expression by malignant cells which enhances tumor cell-platelet binding and hematogenous metastasis. Hypoxia-induced upregulation of TF appears to parallel that of VEGF, although the mechanism remains unclear.

DR/CLIP (class II-associated invariant chain peptides) and DR/peptide complexes colocalize in prelysosomes in human B lymphoblastoid cells

In APCs, MHC class II molecules (MHC class II) bind antigenic peptides after HLA-DM mediated removal of CLIP. To characterize intracellular sites of peptide loading in human B lymphoblastoid cell lines, we conducted immunoelectron microscopy studies with Abs recognizing MHC class II associated with CLIP or bound peptide, respectively, together with Abs to HLA-DM and endocytic markers. The distribution of these molecules indicates that peptide binding occurs in compartments with characteristics of normal late endosomes, and in compartments that show characteristics of late endosomes, but are not detectably accessed by endocytosed BSA-gold. The latter compartments may represent or give rise to recycling vesicles that deliver peptide-loaded class II molecules to the cell surface. In addition, we have compared cells in which HLA-DM and HLA-DR interaction is defective with cells in which this interaction is intact, and find that DM/DR interaction is not required for the proper localization of either molecule to peptide-loading compartments.

The structure of an intermediate in class II MHC maturation: CLIP bound to HLA-DR3

A complex between HLA-DR3 and a fragment of invariant chain called CLIP was isolated from a human cell line defective in antigen presentation and its X-ray crystal structure determined. Previous data indicate that this complex is an intermediate in class II histocompatibility maturation, occurring between invariant chain-DR3 and antigenic peptide-DR3 complexes. The structure shows that the CLIP fragment binds to DR3 in a way almost identical to that in which antigenic peptides bind class II histocompatibility glycoproteins. The structure is the substrate for the loading of antigenic peptides by an exchange process catalysed by DM.

Mediation by HLA-DM of dissociation of peptides from HLA-DR

Human leukocyte antigen (HLA)-DM is an unconventional major histocompatibility complex (MHC) class II heterodimer that is important for B-cell-mediated antigen processing and presentation to MHC class II-restricted T cells. HLA-DM is encoded by two genes, DMA and DMB, which map to the MHC class II region, and shares some homology with MHC class I and class II proteins. Here we define the biochemical role of HLA-DM. Recombinant soluble HLA-DM heterodimers have been purified from culture supernatants of insect cell transformants. At pH 5.0, they induce the dissociation of a subset of peptides bound to HLA-DR, including a nested set of class-II-associated invariant chain peptides (CLIP). This process liberates HLA-DR and leads to the enhanced binding of exogenous peptides.

The role of religion in heart-transplant recipients' long-term health and well-being

While religion has long been recognized clinically to provide important coping strategies in the face of serious health problems, there has been little systematic consideration of its role in organ transplant recipients' long-term reactions and adjustment to this experience. This study examines these issues through qualitative and quantitative evaluation of longitudinal data collected from 40 adult heart recipients followed during their first year post-transplant. Large proportions of recipients expressed strong beliefs and were able to increase religious participation over the 12-month study period. They delineated specific ways in which their faith had provided them support, as well as ways in which the transplant experience itself further strengthened their beliefs. We found empirical evidence that recipients with strong beliefs who participated in religious activities had better physical and emotional well-being, fewer health worries, and better medical compliance by the final 12-month assessment. The findings suggest the development of specific nursing, social-service, or pastoral-involvement strategies, continuing staff education about the role of religion in patient care. The implications of such interventions for maximizing quality of life in transplant recipients are discussed.

An essential role for HLA-DM in antigen presentation by class II major histocompatibility molecules

In antigen-presenting cells, class II molecules of the major histocompatibility complex (MHC) bind peptides derived from endocytosed proteins. In certain B-lymphoblastoid cell mutants, MHC class II molecule-peptide complex formation is impaired, resulting in deficient antigen-presenting function. MHC deletion mutants with this defect map the responsible gene(s) to the class II region of the MHC. Here we report that multiple independent mutants with the class II presentation defect harbour lesions in HLA-DMB, an MHC-linked gene encoding a class II-like beta-chain. Expression of DMB complementary DNA in mutants lacking DMB messenger RNA restores the wild-type phenotype. These results establish HLA-DM as a critical regulatory molecule in class II-restricted antigen presentation and suggest that it functions at an intracellular site to promote class II molecule-peptide association.

Oligo-2',5'-adenylate synthetase in pulmonary sarcoidosis and idiopathic pulmonary fibrosis

Oligo-2',5'-adenylate synthetase (2,5AS) is an enzyme induced by all types of interferon (IFN). We measured the levels of 2,5AS activity in peripheral blood mononuclear leukocytes (PBML) and bronchoalveolar lavage fluid (BALF) cells of patients with pulmonary sarcoidosis (SAR), idiopathic pulmonary fibrosis (IPF), and normal controls (NC). In NC, the levels of BALF cell 2,5AS activity were approximately seven times as high as the levels of PBML 2,5AS activity. The measurement 2,5AS activity from isolated cells showed that the levels of 2,5AS activity are independent of cell differential from PBML and BALF cells. The levels of PBML and BALF cell 2,5AS activity in SAR were both significantly high in comparison with those in NC. In patients with IPF, the levels of PBML 2,5AS activity were significantly increased as compared with those in NC, whereas there was no significant difference regarding the levels of BALF cell 2,5AS activity between patients with IPF and NC. These results suggest the following: (1) in patients with SAR, IFN production is enhanced both in the alveolar space and peripheral circulation; (2) in patients with IPF, IFN production is greatly enhanced in the circulation, whereas IFN production is not enhanced in the alveolar space; and (3) IFN may contribute to the pathogenesis of SAR and IPF.

A mutant human histocompatibility leukocyte antigen DR molecule associated with invariant chain peptides

From a human histocompatibility leukocyte antigen (HLA)-DR/DQ hemizygous, B lymphoblastoid progenitor, we isolated a cell line, 10.24.6, with a DR alpha missense mutation (96P-->96S), which results in an N-linked carbohydrate addition at position 94 in the DR alpha 2 domain. Several features of 10.24.6 cells suggest that the mutation disrupts normal intracellular formation of peptide/DR complexes. The mutant HLA-DR dimers, though expressed at the cell surface, lack the conformation of the mature, peptide-loaded class II molecules of the progenitor cell, as assessed by their loss of binding of certain antibodies and by the lack of stability in detergent (sodium dodecyl sulfate) solution. In addition, presentation of endocytosed antigen to HLA-DR-restricted T cells is defective in the mutant, but can be restored by transfection of a wild type DRA gene. Assays with synthetic peptides indicate that the 10.24.6 phenotype is not due to an intrinsic inability of the mutant DR molecules to bind peptides. Therefore, to directly evaluate peptide occupancy of the mutant molecules, we analyzed acid-eluted, HLA-DR-associated peptides. The predominant species from the 10.24.6 mutant is a nested set of invariant chain (Ii)-derived peptides that are undetectable in the DR eluate from progenitor cells. The region of DR alpha altered in the mutant molecules is thus implicated in normal formation of peptide/DR complexes. Further, the same set of Ii peptides associated with the DR molecules is present in the eluate from an antigen presentation mutant with a defect in an major histocompatibility complex (MHC)-linked gene. These results suggest that DR molecules in 10.24.6 and in certain presentation mutants are affected at the same or related steps in class II molecule biosynthesis, raising the possibility that class II molecules interact with an MHC-encoded accessory molecule during antigen presentation.