Smoking Is Associated with Higher Disease Activity in Rheumatoid Arthritis: A Longitudinal Study Controlling for Time-varying Covariates

OBJECTIVE

Prior studies around the relationship between smoking and rheumatoid arthritis (RA) disease activity have reported inconsistent findings, which may be ascribed to heterogeneous study designs or biases in statistical analyses. We examined the association between smoking and RA outcomes using statistical methods that account for time-varying confounding and loss to followup.

METHODS

We included 282 individuals with an RA diagnosis using electronic health record data collected at a public hospital between 2013 and 2017. Current smoking status and disease activity were assessed at each visit; covariates included sex, race/ethnicity, age, obesity, and medication use. We used longitudinal targeted maximum likelihood estimation to estimate the causal effect of smoking on disease activity measures at 27 months, and compared results to conventional longitudinal methods.

RESULTS

Smoking was associated with an increase of 0.64 units in the patient global score compared to nonsmoking (p = 0.01), and with 2.58 more swollen joints (p < 0.001). While smoking was associated with a higher clinical disease activity score (2.11), the difference was not statistically significant (p = 0.22). We found no association between smoking and physician global score, or C-reactive protein levels, and an inverse association between smoking and tender joint count (p = 0.05). Analyses using conventional methods showed a null relationship for all outcomes.

CONCLUSION

Smoking is associated with higher levels of disease activity in RA. Causal methods may be useful for investigations of additional exposures on longitudinal outcome measures in rheumatologic disease.

Hypomethylation of CYP2E1 and DUSP22 Promoters Associated With Disease Activity and Erosive Disease Among Rheumatoid Arthritis Patients

Objective

Epigenetic modifications have previously been associated with rheumatoid arthritis (RA). In this study, we aimed to determine whether differential DNA methylation in peripheral blood cell subpopulations is associated with any of 4 clinical outcomes among RA patients.

Methods

Peripheral blood samples were obtained from 63 patients in the University of California, San Francisco RA cohort (all satisfied the American College of Rheumatology classification criteria; 57 were seropositive for rheumatoid factor and/or anti‐cyclic citrullinated protein). Fluorescence‐activated cell sorting was used to separate the cells into 4 immune cell subpopulations (CD14+ monocytes, CD19+ B cells, CD4+ naive T cells, and CD4+ memory T cells) per individual, and 229 epigenome‐wide DNA methylation profiles were generated using Illumina HumanMethylation450 BeadChips. Differentially methylated positions and regions associated with the Clinical Disease Activity Index score, erosive disease, RA Articular Damage score, Sharp score, medication at time of blood draw, smoking status, and disease duration were identified using robust regression models and empirical Bayes variance estimators.

Results

Differential methylation of CpG sites associated with clinical outcomes was observed in all 4 cell types. Hypomethylated regions in the CYP2E1 and DUSP22 gene promoters were associated with active and erosive disease, respectively. Pathway analyses suggested that the biologic mechanisms underlying each clinical outcome are cell type–specific. Evidence of independent effects on DNA methylation from smoking, medication use, and disease duration were also identified.

Conclusion

Methylation signatures specific to RA clinical outcomes may have utility as biomarkers or predictors of exposure, disease progression, and disease severity.

Use of Low-Literacy Decision Aid to Enhance Knowledge and Reduce Decisional Conflict Among a Diverse Population of Adults With Rheumatoid Arthritis: Results of a Pilot Study

OBJECTIVE

Despite innovations in treatment of rheumatoid arthritis (RA), adherence is poor and disparities persist. Shared decision making (SDM) promotes patient engagement and enhances adherence; however, few tools support SDM in RA. Our objective was to pilot a low-literacy medication guide and decision aid to facilitate patient-clinician conversations about RA medications.

METHODS

RA patients were consecutively enrolled into 1 of 3 arms: 1) control; patients received existing medication guide prior to clinic visit, 2) adapted guide prior to visit, and 3) adapted guide prior to plus decision aid during visit. Outcomes were collected immediately postvisit, at 1-week, and at 3- and 6-month interviews. Eligible adults had to have failed at least 1 disease-modifying antirheumatic drug and fulfill 1 of the following: age >65 years, immigrant, non-English speaker, less than high school education, limited health literacy, and racial/ethnic minority. Primary outcomes were knowledge of RA medications, decisional conflict, and acceptability of interventions.

RESULTS

The majority of 166 patients were immigrants (66%), non-English speakers (54%), and had limited health literacy (71%). Adequate RA knowledge postvisit in arm 3 was higher (78%) than arm 1 (53%; adjusted odds ratio 2.7, 95% confidence interval 1.2, 6.1). Among patients with a medication change, there was lower (better) mean decisional conflict in arms 2 and 3 (P = 0.03). There were no significant differences in acceptability.

CONCLUSION

A low-literacy medication guide and decision aid was acceptable, improved knowledge, and reduced decisional conflict among vulnerable RA patients. Enhancing knowledge and patient engagement with decision support tools may lead to medication choices better aligned with RA patients' values and preferences.

Evaluating radiocarpal cartilage matrix changes 3-months after anti-TNF treatment for rheumatoid arthritis using MR T1ρ imaging

PURPOSE

To evaluate the feasibility of MR T1ρ in assessing radiocarpal cartilage matrix changes following rheumatoid arthritis (RA) treatment.

MATERIALS AND METHODS

Five healthy controls and nine RA patients were studied: three RA patients with low disease activity that were treated with methotrexate (MTX) alone and six with active disease despite MTX treatment who were additionally treated with certolizumab pegol, an anti-tumor necrosis factor biologic. Wrist 3 Tesla MRI were acquired at baseline and 3-month follow-up. T1ρ were quantified for lunar, radius, and scaphoid cartilage. Reproducibility was evaluated using coefficients of variation (CV). Longitudinal changes were evaluated with t-test and relationships between T1ρ with clinical, MRI, and patient-reported outcomes were evaluated with Spearman's rho.

RESULTS

Scan/re-scan CVs of T1ρ values were all <5%, and intra- and inter-reader CVs were all < 2.0%. Baseline scaphoid T1ρ values were significantly higher in RA patients compared with healthy controls (P = 0.032). Changes in T1ρ (baseline, 3-month) were correlated with EULAR treatment response criteria: -2.26 ± 0.75 ms, 1.08 ± 0.52 ms, and 2.18 ± 0.45 ms for good, moderate, and nonresponders, respectively. Significant correlations were found between changes in global T1ρ values and changes in DAS28-CRP (r_s  = 0.683; P = 0.042), MHQ (r_s  = -0.783; P = 0.013), and HAQ (r_s  = 0.833; P = 0.010).

CONCLUSION

Despite the limited sample size and follow-up time points, there were significant correlations between changes in radiocarpal T1ρ and changes in disease activity as assessed by clinical and patient-reported outcomes. Our findings encourage further research into MR T1ρ assessment of RA disease activity and treatment response.

LEVEL OF EVIDENCE

1 J. MAGN. RESON. IMAGING 2017;45:1514-1522.

High-temporospatial-resolution dynamic contrast-enhanced (DCE) wrist MRI with variable-density pseudo-random circular Cartesian undersampling (CIRCUS) acquisition: evaluation of perfusion in rheumatoid arthritis patients

This study is to evaluate highly accelerated three-dimensional (3D) dynamic contrast-enhanced (DCE) wrist MRI for assessment of perfusion in rheumatoid arthritis (RA) patients. A pseudo-random variable-density undersampling strategy, circular Cartesian undersampling (CIRCUS), was combined with k-t SPARSE-SENSE reconstruction to achieve a highly accelerated 3D DCE wrist MRI. Two healthy volunteers and 10 RA patients were studied. Two patients were on methotrexate (MTX) only (Group I) and the other eight were treated with a combination therapy of MTX and anti-tumor necrosis factor (TNF) therapy (Group II). Patients were scanned at baseline and 3 month follow-up. DCE MR images were used to evaluate perfusion in synovitis and bone marrow edema pattern in the RA wrist joints. A series of perfusion parameters was derived and compared with clinical disease activity scores of 28 joints (DAS28). 3D DCE wrist MR images were obtained with a spatial resolution of 0.3 × 0.3 × 1.5 mm(3) and temporal resolution of 5 s (with an acceleration factor of 20). The derived perfusion parameters, most notably transition time (dT) of synovitis, showed significant negative correlations with DAS28-ESR (r = -0.80, p < 0.05) and DAS28-CRP (r = -0.87, p < 0.05) at baseline and also correlated significantly with treatment responses evaluated by clinical score changes between baseline and 3 month follow-up (with DAS28-ESR r = -0.79, p < 0.05, and DAS28-CRP r = -0.82, p < 0.05). Highly accelerated 3D DCE wrist MRI with improved temporospatial resolution has been achieved in RA patients and provides accurate assessment of neovascularization and perfusion in RA joints, showing promise as a potential tool for evaluating treatment responses.

English language proficiency, health literacy, and trust in physician are associated with shared decision making in rheumatoid arthritis

OBJECTIVE

Treat-to-target guidelines promote shared decision making (SDM) in rheumatoid arthritis (RA). Also, because of high cost and potential toxicity of therapies, SDM is central to patient safety. Our objective was to examine patterns of perceived communication around decision making in 2 cohorts of adults with RA.

METHODS

Data were derived from patients enrolled in 1 of 2 longitudinal, observational cohorts [University of California, San Francisco (UCSF) RA Cohort and RA Panel Cohort]. Subjects completed a telephone interview in their preferred language that included a measure of patient-provider communication, including items about decision making. Measures of trust in physician, education, and language proficiency were also asked. Logistic regression was performed to identify correlates of suboptimal SDM communication. Analyses were performed on each sample separately.

RESULTS

Of 509 patients across 2 cohorts, 30% and 32% reported suboptimal SDM communication. Low trust in physician was independently associated with suboptimal SDM communication in both cohorts. Older age and limited English proficiency were independently associated with suboptimal SDM in the UCSF RA Cohort, as was limited health literacy in the RA Panel Cohort.

CONCLUSION

This study of over 500 adults with RA from 2 demographically distinct cohorts found that nearly one-third of subjects report suboptimal SDM communication with their clinicians, regardless of cohort. Lower trust in physician was independently associated with suboptimal SDM communication in both cohorts, as was limited English language proficiency and older age in the UCSF RA Cohort and limited health literacy in the RA Panel Cohort. These findings underscore the need to examine the influence of SDM on health outcomes in RA.

Depletion of B-cells with rituximab improves endothelial function and reduces inflammation among individuals with rheumatoid arthritis

Background

Individuals with rheumatoid arthritis (RA) are at increased risk for cardiovascular disease, partly due to systemic inflammation and endothelial dysfunction. B‐cells play an important pathogenic role in the inflammatory process that drives RA disease activity. Rituximab, a chimeric murine/human monoclonal antibody that depletes B‐cells, is an effective therapy for RA. The purpose of this study was to determine whether B‐cell depletion with rituximab reduces systemic inflammation and improves macrovascular (brachial artery flow‐mediated dilation, FMD) and microvascular (reactive hyperemia) endothelial function in RA patients.

Methods and Results

RA patients received a single course of rituximab (1000 mg IV infusion at baseline and on day 15). FMD, reactive hyperemia, inflammatory markers, and clinical assessments were performed at baseline, week 12, and week 24. Twenty patients (95% female, median age 54 years) completed the study. Following treatment, FMD improved from a baseline of 4.5±0.4% to 6.4±0.6% at 12 weeks (mean±SE; P<0.0001), followed by a decline at week 24; a similar pattern was observed for hyperemic velocity. Significant decreases in RA disease scores, high‐sensitivity C‐reactive protein, erythrocyte sedimentation rate, and circulating CD19+ B‐cells were sustained through week 24. Cholesterol and triglycerides became significantly although modestly elevated during the study.

Conclusions

Depletion of B‐cells with rituximab improved macrovascular and microvascular endothelial function and reduced systemic inflammation, despite modest elevation in lipids. Given these results, rituximab should be evaluated in the future for its possible role in reducing excess cardiovascular risk in RA.

Clinical Trial Registration

URL http://ClinicalTrials.gov. Unique identifier: NCT00844714.

Poor knowledge of methotrexate associated with older age and limited English-language proficiency in a diverse rheumatoid arthritis cohort

Introduction

Our objective was to determine rheumatoid arthritis (RA) patients’ understanding of methotrexate and assess whether knowledge varies by age, education, English language proficiency, or other disease-related factors.

Methods

Adults with RA (n = 135) who were enrollees of an observational cohort completed a structured telephone interview in their preferred language between August 2007 and July 2009. All subjects who reported taking methotrexate were asked 11 questions about the medication in addition to demographics, education level, and language proficiency. Primary outcome was a total score below the 50^th percentile (considered inadequate methotrexate knowledge). Bivariable and multivariable logistic regressions were performed. Covariates included demographics, language proficiency, education, and disease characteristics.

Results

Of 135 subjects, 83% were female, with a mean age of 55 ± 14 years. The majority spoke English (64%), followed by 22% Spanish and 14% Cantonese or Mandarin. Limited English language proficiency (LEP) was reported in 42%. Mean methotrexate knowledge score was 5.4 ± 2.6 (range, 0 to 10); 73 (54%) had a score lower than 5 (of 10). Age older than 55, less than high school education, LEP, better function, and biologic use were independently associated with poor knowledge.

Conclusions

In a diverse RA cohort, overall methotrexate knowledge was poor. Older age and limited proficiency in English were significant correlates of poor knowledge. Identification of language barriers and improved clinician-patient communication around methotrexate dosing and side effects may lead to improved safety and enhanced benefits of this commonly used RA medication.

Methotrexate and a spleen tyrosine kinase inhibitor cooperate to inhibit responses to peripheral blood B cells in rheumatoid arthritis

BACKGROUND

Selective disruption of the spleen tyrosine kinase (Syk) represents a novel strategy to control B-cell functional responses by inhibition of B-cell antigen receptor (BCR) signaling. PRT062607 (P505-15) is a highly selective small molecule Syk inhibitor that potently suppresses B-cell function in human and rodent blood, and reduces inflammation in rodent models of rheumatoid arthritis (RA).

AIMS

In this study, we sought to determine the potency of Syk inhibition by PRT062607 in whole blood from RA patients, and elucidate covariates that affect the potency of immune-regulation by this compound.

MATERIALS AND METHODS

Whole blood was collected from 30 patients diagnosed with RA as part of a single-center outpatient study. Disease severity, serum protein markers of inflammation, and co-medications were related to each other, and to PRT062607 activity in ex vivo Syk-mediated immune function assays.

RESULTS

We report here that PRT062607 exhibited greater potency in suppressing BCR mediated B-cell functional responses in whole blood from RA patients who received stable methotrexate (MTX) therapy. We demonstrate that the B-cell functional response to BCR ligation is influenced by cytokines and JAK/STAT signaling.

DISCUSSION

MTX is a known cytokine modulating agent, and this mechanism may act in concert with PRT062607 to control B-cell function.

CONCLUSION

These data have important implications for the co-administration of Syk inhibitors and MTX for the treatment of RA.

Purpura, cutaneous necrosis, and antineutrophil cytoplasmic antibodies associated with levamisole-adulterated cocaine

OBJECTIVE

To describe the clinical and serologic abnormalities in 6 patients who presented with retiform purpura and extensive cutaneous necrosis after exposure to levamisole-adulterated cocaine.

METHODS

All patients were evaluated at San Francisco General Hospital or the University of California San Francisco Medical Center. Each underwent standard screening for substances of abuse and had urine tested for the presence of levamisole by liquid chromatography tandem mass spectrometry. Routine laboratory, autoantibody, and antiphospholipid antibody testing was performed in the hospitals' clinical or reference laboratories. Testing for atypical antineutrophil cytoplasmic antibodies (ANCAs) was performed separately using commercially available enzyme-linked immunosorbent assay kits.

RESULTS

The patients were women ages 39-50 years who presented with retiform purpura and cutaneous necrosis. Skin biopsies revealed a predominantly small-vessel thrombotic vasculopathy with varying degrees of vasculitis. Four patients were neutropenic. All tested positive for lupus anticoagulant, had IgM antibodies to cardiolipin, and tested strongly positive for ANCAs in a perinuclear pattern by immunofluorescence. Each patient had antibodies to multiple components of neutrophil granules, including neutrophil elastase, lactoferrin, cathepsin G, proteinase 3, and myeloperoxidase.

CONCLUSION

Rheumatologists should be aware of this distinctive form of necrotic purpura, its associated autoantibodies, and its link to levamisole-adulterated cocaine.

Racial and ethnic disparities in disease activity and function among persons with rheumatoid arthritis from university-affiliated clinics

OBJECTIVE

Health outcomes in rheumatoid arthritis (RA) have improved significantly over the past 2 decades. However, research suggests that disparities exist by race/ethnicity and socioeconomic status, with certain vulnerable populations remaining understudied. Our objective was to assess disparities in disease activity and function by race/ethnicity and explore the impact of language and immigrant status at clinics serving diverse populations.

METHODS

We examined a cross-sectional study of 498 adults with confirmed RA at 2 rheumatology clinics: a university hospital clinic and a public county hospital clinic. Outcomes included the Disease Activity Score in 28 joints (DAS28) and its components, and the Health Assessment Questionnaire (HAQ), a measure of function. We estimated multivariable linear regression models including interaction terms for race/ethnicity and clinic site.

RESULTS

After adjusting for age, sex, education, disease duration, rheumatoid factor status, and medication use, clinically meaningful and statistically significant differences in DAS28 and HAQ scores were seen by race/ethnicity, language, and immigrant status. Lower disease activity and better function was observed among whites compared to nonwhites at the university hospital. This same pattern was observed for disease activity by language (English compared to non-English) and immigrant status (US-born compared to immigrant) at the university clinic. No significant differences in outcomes were found at the county clinic.

CONCLUSION

The relationship between social determinants and RA disease activity varied significantly across clinic setting with pronounced variation at the university, but not at the county clinic. These disparities may be a result of events that preceded access to subspecialty care, poor adherence, or health care delivery system differences.

Quantitative characterization of bone marrow edema pattern in rheumatoid arthritis using 3 Tesla MRI

PURPOSE

To develop imaging techniques that provide quantitative characterization of bone marrow edema pattern (BME) in wrist joints of patients with rheumatoid arthritis (RA), including volume, signal intensity changes, and perfusion properties.

MATERIALS AND METHODS

Fourteen RA patients and three controls were scanned using 3 Tesla MR. BME was semi-automatically segmented in water images obtained from iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) sequences. BME perfusion parameters (enhancement and slope) were evaluated using three-dimensional (3D) dynamic enhanced MRI (DCE-MRI). Experimental reproducibility, inter- and intra-observer reproducibility of BME quantification were evaluated using root mean square coefficients of variation (RMS-CV) and intraclass correlation (ICC).

RESULTS

The RMS-CV for BME volume quantification with repeated scans were 6.9%. The inter-observer ICC was 0.993 and RMS CV was 5.2%. The intra-observer ICC was 0.998 and RMS CV was 2.3%. Both maximum enhancement and slope during DCE-MRI were significantly higher in BME than in normal bone marrow (P < 0.001). No significant correlation was found between BME quantification and clinical evaluations.

CONCLUSION

A highly reproducible semi-automatic method for quantifying BME lesion burden in RA was developed, which may enhance our capability of predicting disease progression and monitoring treatment response.

Socioeconomic determinants of disability and depression in patients with rheumatoid arthritis

OBJECTIVE

To examine the relationship between functional limitation, socioeconomic inequality, and depression in a diverse cohort of patients with rheumatoid arthritis (RA).

METHODS

The study design was cross-sectional and subjects were from the University of California, San Francisco RA Cohort. Patients were enrolled from 2 rheumatology clinics, an urban county public hospital and a university tertiary care medical center. Age, sex, race/ethnicity, disease activity, functional limitation, and medications were variables collected at clinical visits. The patient's clinic site was used as a proxy for his or her socioeconomic status. The outcome variable was depressive symptom severity measured by the Patient Health Questionnaire 9. Differences in characteristics between depressed and nondepressed patients were calculated using 2-sided t-tests or the Pearson's chi-square test. For the multivariate analysis, repeated measures with generalized estimating equations were used.

RESULTS

There were statistically significant differences between depressed and nondepressed patients related to race/ethnicity, public versus tertiary care hospital rheumatology clinic, disability, and medications. In the multivariate analysis, increased functional limitation and public clinic site remained significantly associated with increased depression scores. A significant interaction existed between clinic site and disability. Mean depression scores rose more precipitously as functional limitation increased at the public hospital rheumatology clinic.

CONCLUSION

There are disparities in both physical and mental health among individuals with low socioeconomic status. The psychological effects of disability vary in patients with RA such that a vulnerable population with functional limitations is at higher risk of developing depressive symptoms.

Patient-physician discordance in assessments of global disease severity in rheumatoid arthritis

OBJECTIVE

To determine the degree of discordance between patient and physician assessment of disease severity in a multiethnic cohort of adults with rheumatoid arthritis (RA), to explore predictors of discordance, and to examine the impact of discordance on the Disease Activity Score in 28 joints (DAS28).

METHODS

Adults with RA (n = 223) and their rheumatologists completed a visual analog scale (VAS) for global disease severity independently. Patient demographics, the 9-item Patient Health Questionnaire (PHQ-9) depression scale score, the Health Assessment Questionnaire score, and the DAS28 were also collected. Logistic regression analyses were used to identify predictors of positive discordance, defined as a patient rating minus physician rating of >25 mm on a 100-mm VAS (considered clinically relevant). DAS28 scores stratified by level of discordance were compared using a paired t-test.

RESULTS

Positive discordance was found in 30% of cases, with a mean +/- SD difference of 46 +/- 15. The strongest independent predictor of discordance was a 5-point increase in PHQ-9 score (adjusted odds ratio 1.61, 95% confidence interval 1.02-2.55). Higher swollen joint count and Cantonese/Mandarin language were associated with lower odds of discordance. DAS28 scores were most divergent among subjects with discordance.

CONCLUSION

Nearly one-third of RA patients differed from their physicians to a meaningful degree in assessment of global disease severity. Higher depressive symptoms were associated with discordance. Further investigation of the relationships between mood, disease activity, and discordance may guide interventions to improve care for adults with RA.

Predictors of depression in a multiethnic cohort of patients with rheumatoid arthritis

OBJECTIVE

Patients with rheumatoid arthritis (RA) who experience depression have worse health outcomes. This study identifies predictors of depression in an ethnically and racially diverse population of patients with RA.

METHODS

Patients with RA in a prospective cohort at the San Francisco General Hospital outpatient rheumatology clinic were included if they were age >or=18 years, met the American College of Rheumatology classification criteria for RA, had a Health Assessment Questionnaire (HAQ) score collected, and had the RA-specific Disease Activity Score performed by a rheumatologist. The outcome variable was a depression score measured by the Patient Health Questionnaire 9 (PHQ-9), a self-report questionnaire validated to correlate with a diagnosis of major depression.

RESULTS

Three hundred forty-nine clinical visits for 172 patients were included in the analysis. Forty percent of patients scored >or=10 on the PHQ-9 during at least one clinic visit, which corresponds to a symptom severity of at least moderate depression. The mean PHQ-9 score was 7, corresponding to a symptom severity of mild depression. In the multivariate analysis, higher HAQ scores were associated with depression, and Asians had lower depression scores compared with Hispanic, white, and African American subjects.

CONCLUSION

Identifying associated predictors of depression in a diverse population of patients with RA can help guide treatment, which should include preventing disability and decreased function as well as targeting depressive symptoms more specifically in patients with RA.

Distinct regions in the CD28 cytoplasmic domain are required for T helper type 2 differentiation

CD28 costimulation is essential for CD4(+) T cell proliferation, survival, interleukin 2 (IL-2) production and T helper type 2 development. To define the nature of the signals that may drive different T cell responses, we have done a structure-function analysis of the CD28 cytoplasmic tail in primary T cells. CD28-mediated T cell proliferation and IL-2 production did not require a particular cytoplasmic domain. In contrast, IL-4 production was driven by the cooperative activity of specific motifs within the CD28 cytoplasmic tail. Using a gene-complementation approach, we provide evidence that one component of this T helper type 2 differentiation signal was mediated by 3-phosphoinositide-dependent protein kinase 1. Thus, different mechanisms underlie the induction of distinct T cell functional responses by CD28.

Phosphatidylinositol 3-Kinase Is Required for CD28 But Not CD3 Regulation of the TEC Family Tyrosine Kinase EMT/ITK/TSK: Functional and Physical Interaction of EMT with Phosphatidylinositol 3-Kinase

Ligation of the TCR or CD28 induces activation of phosphatidylinositol 3-kinase (PI3K), the TEC family protein tyrosine kinase, EMT/ITK/TSK (EMT), and the SRC family tyrosine kinase, LCK. LCK is required for the activation and phosphorylation of EMT induced by ligation of the TCR or CD28 placing LCK upstream of EMT in T cell signaling cascades. We report herein that inhibition of PI3K activity with the specific inhibitors LY294002 and wortmannin markedly decreased EMT activation induced by CD28 cross-linking but not by CD3 cross-linking. Further, inhibition of PI3K markedly decreased EMT in vitro autokinase activity induced by activated LCK. In contrast, PI3K inhibitors did not alter CD28 or CD3 cross-linking or LCK-induced EMT phosphorylation. Consistent with the requirement of PI3K activity for CD28 but not CD3-induced stimulation of the EMT in vitro autokinase activity, a small but significant portion of cellular EMT associates with PI3K following CD28 cross-linking but not following CD3 cross-linking. CD28-induced association of EMT with PI3K also requires functional expression of LCK. Fusion proteins containing the SRC homology 2 domain of EMT interact with PI3K or a PI3K-associated molecule in a tyrosine phosphorylation-dependent manner. Taken together, the data suggest that EMT is differentially regulated and recruited to different signaling complexes following ligation of CD28 or the TCR complex, perhaps contributing to the disparate roles that EMT appears to play downstream of CD28 and the TCR.

Phosphatidylinositol 3-kinase is required for CD28 but not CD3 regulation of the TEC family tyrosine kinase EMT/ITK/TSK: functional and physical interaction of EMT with phosphatidylinositol 3-kinase

Ligation of the TCR or CD28 induces activation of phosphatidylinositol 3-kinase (PI3K), the TEC family protein tyrosine kinase, EMT/ITK/TSK (EMT), and the SRC family tyrosine kinase, LCK. LCK is required for the activation and phosphorylation of EMT induced by ligation of the TCR or CD28 placing LCK upstream of EMT in T cell signaling cascades. We report herein that inhibition of PI3K activity with the specific inhibitors LY294002 and wortmannin markedly decreased EMT activation induced by CD28 cross-linking but not by CD3 cross-linking. Further, inhibition of PI3K markedly decreased EMT in vitro autokinase activity induced by activated LCK. In contrast, PI3K inhibitors did not alter CD28 or CD3 cross-linking or LCK-induced EMT phosphorylation. Consistent with the requirement of PI3K activity for CD28 but not CD3-induced stimulation of the EMT in vitro autokinase activity, a small but significant portion of cellular EMT associates with PI3K following CD28 cross-linking but not following CD3 cross-linking. CD28-induced association of EMT with PI3K also requires functional expression of LCK. Fusion proteins containing the SRC homology 2 domain of EMT interact with PI3K or a PI3K-associated molecule in a tyrosine phosphorylation-dependent manner. Taken together, the data suggest that EMT is differentially regulated and recruited to different signaling complexes following ligation of CD28 or the TCR complex, perhaps contributing to the disparate roles that EMT appears to play downstream of CD28 and the TCR.

Turning off natural killers. Innate immunity

Inhibitory receptors specific for class I molecules of the major histocompatibility complex regulate the cytolytic activity of natural killer cells. Recent studies suggest that recruitment of the protein tyrosine phosphatase SHP-1 enables these receptors to block natural killing.

Role of p85 subunit of phosphatidylinositol-3-kinase as an adaptor molecule linking the insulin receptor to insulin receptor substrate 1

After insulin stimulation of cells, signaling complexes are formed, containing the insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and phosphatidylinositol-3-kinase. To study the nature of these complexes, we employed purified IR, recombinant IRS-1, antibodies to IR and IRS-1, and fusion proteins containing the two SH2 domains of p85. In intact cells, insulin increased tyrosine phosphorylation of both the IR and IRS-1. Both of these proteins were immunoprecipitated with antibodies to p85. Also, fusion proteins containing the two SH2 domains of p85 directly precipitated both the IR and IRS-1. Next, these signaling complexes were reconstituted in vitro with purified IR, recombinant IRS-1, and the two SH2 domains of p85. In the presence of both SH2 domains of p85, the IR associated with IRS-1. Other data, both in intact cells and in vitro, demonstrated that N- and C-terminal SH2 domains of p85 had preferential binding affinities for the IR and IRS-1, respectively. Studies with an IR mutant truncated in the C terminus indicated that the C-terminal phosphotyrosines of the IR play a major role in interacting with the SH2 domains of p85. In conclusion, both in vivo and in vitro data support a role for p85 in directly linking the IR to IRS-1 via its SH2 domains. The formation of these complexes, therefore, may provide a mechanism for the translocation to the plasma membrane of phosphatidylinositol-3-kinase and other molecules that are involved in IR signaling.

The role of protein kinase C in transmembrane signaling by the T cell antigen receptor complex. Effects of stimulation with soluble or immobilized CD3 antibodies

Phorbol esters, such as phorbol myristate acetate (PMA), are known to be potent co-stimulants with calcium ionophores for activation of T lymphocytes. The most extensively studied intracellular effect of PMA is its ability to activate the cytoplasmic enzyme protein kinase C (pkC). Herein, we examined the role of pkC activation during T cell activation. During physiologic activation, this enzyme is activated by diacylglycerol which is generated through the hydrolysis of polyphosphoinositides. Therefore, we studied the activation of T lymphocytes induced by a synthetic diacylglycerol, dioctanoylglycerol. In contrast to PMA, this compound can be metabolized in T cells and presumably more closely mimics physiologic activation of pkC. Dioctanoylglycerol together with reagents that induce increases in intracellular free Ca2+ concentration, Ca2+ ionophores, or anti-cluster designation (CD)3 monoclonal antibodies (mAb) were able to induce interleukin 2 receptor expression and proliferation of T lymphocytes. Previous studies have demonstrated that the stimulation of T cells via the CD3/T cell antigen receptor complex by mAb against CD3 leads to an increase in cytoplasmic free Ca2+ and to an activation of pkC. Paradoxically, however, soluble CD3 antibodies do not cause proliferation of resting purified T cells. Inasmuch as immobilization of CD3 mAb has been shown to influence the agonist properties of such antibodies, we compared the ability of soluble and immobilized CD3 mAb to activate pkC. We demonstrated herein that soluble CD3 mAb cause only a very transient activation of pkC in the T cell leukemic line Jurkat. This pkC activation is markedly prolonged when Jurkat cells are stimulated with immobilized rather than soluble CD3 antibodies. These studies suggest that activation of pkC plays a major role in T cell activation and that the activation of pkC is influenced by the form in which CD3 mAb is presented to T cells.

The role of protein kinase C in transmembrane signaling by the T cell antigen receptor complex. Effects of stimulation with soluble or immobilized CD3 antibodies

Phorbol esters, such as phorbol myristate acetate (PMA), are known to be potent co-stimulants with calcium ionophores for activation of T lymphocytes. The most extensively studied intracellular effect of PMA is its ability to activate the cytoplasmic enzyme protein kinase C (pkC). Herein, we examined the role of pkC activation during T cell activation. During physiologic activation, this enzyme is activated by diacylglycerol which is generated through the hydrolysis of polyphosphoinositides. Therefore, we studied the activation of T lymphocytes induced by a synthetic diacylglycerol, dioctanoylglycerol. In contrast to PMA, this compound can be metabolized in T cells and presumably more closely mimics physiologic activation of pkC. Dioctanoylglycerol together with reagents that induce increases in intracellular free Ca2+ concentration, Ca2+ ionophores, or anti-cluster designation (CD)3 monoclonal antibodies (mAb) were able to induce interleukin 2 receptor expression and proliferation of T lymphocytes. Previous studies have demonstrated that the stimulation of T cells via the CD3/T cell antigen receptor complex by mAb against CD3 leads to an increase in cytoplasmic free Ca2+ and to an activation of pkC. Paradoxically, however, soluble CD3 antibodies do not cause proliferation of resting purified T cells. Inasmuch as immobilization of CD3 mAb has been shown to influence the agonist properties of such antibodies, we compared the ability of soluble and immobilized CD3 mAb to activate pkC. We demonstrated herein that soluble CD3 mAb cause only a very transient activation of pkC in the T cell leukemic line Jurkat. This pkC activation is markedly prolonged when Jurkat cells are stimulated with immobilized rather than soluble CD3 antibodies. These studies suggest that activation of pkC plays a major role in T cell activation and that the activation of pkC is influenced by the form in which CD3 mAb is presented to T cells.

Heterogeneity of signal requirements in T cell activation within a panel of human proliferative T cell clones

Activation of T lymphocytes is initiated by receptor ligand interactions at the cell surface leading to the transduction of intracellular signals followed by the de novo synthesis and expression of T cell activation markers (including receptors for interleukin 2 (IL 2) and transferrin), production of lymphokines, and T cell proliferation. This requisite first step for activation of T lymphocytes can be mimicked in certain situations with a variety of stimuli. These include antibodies to certain integral membrane proteins, phorbol esters, and plant lectins that act as mitogens. In this paper, we report that at least two classes of human T cell clones can be distinguished based upon signal requirements necessary to induce proliferation. Although all clones analyzed expressed IL 2 receptors and secreted IL 2 after non-antigenic activation, one subset of clones did not proliferate in response to the same non-antigenic signals. In that subset, complete activation leading to proliferation required interaction of the T cell with specific antigen. The ability to subset these T cell clones into two groups did not correlate with phenotypic differences, source of the clone, nor with magnitude of intracellular calcium mobilization. By studying the stimulation requirements of these two subsets of human T cell clones through the use of specific antigen or antigen-independent stimuli, it was possible to demonstrate that different stimuli varied in their ability to induce steps of T cell activation. Analysis of reactivity of these clones to suboptimal stimulation allowed the definition of intermediate stages of T cell activation. Such intermediate stages might reflect a diversity of intracellular signaling pathways or a complexity of regulatory mechanisms distal to the events that allow intracellular calcium mobilization. Thus for the first time, it has been possible to study ordered events of T cell activation in non-transformed, antigen-dependent human T lymphocytes. The data presented in this paper suggest that T cell activation is not an all or nothing phenomenon, and there is an ordered sequence of events that can be differentiated based upon signal requirements at the T cell membrane.

Heterogeneity of signal requirements in T cell activation within a panel of human proliferative T cell clones

Activation of T lymphocytes is initiated by receptor ligand interactions at the cell surface leading to the transduction of intracellular signals followed by the de novo synthesis and expression of T cell activation markers (including receptors for interleukin 2 (IL 2) and transferrin), production of lymphokines, and T cell proliferation. This requisite first step for activation of T lymphocytes can be mimicked in certain situations with a variety of stimuli. These include antibodies to certain integral membrane proteins, phorbol esters, and plant lectins that act as mitogens. In this paper, we report that at least two classes of human T cell clones can be distinguished based upon signal requirements necessary to induce proliferation. Although all clones analyzed expressed IL 2 receptors and secreted IL 2 after non-antigenic activation, one subset of clones did not proliferate in response to the same non-antigenic signals. In that subset, complete activation leading to proliferation required interaction of the T cell with specific antigen. The ability to subset these T cell clones into two groups did not correlate with phenotypic differences, source of the clone, nor with magnitude of intracellular calcium mobilization. By studying the stimulation requirements of these two subsets of human T cell clones through the use of specific antigen or antigen-independent stimuli, it was possible to demonstrate that different stimuli varied in their ability to induce steps of T cell activation. Analysis of reactivity of these clones to suboptimal stimulation allowed the definition of intermediate stages of T cell activation. Such intermediate stages might reflect a diversity of intracellular signaling pathways or a complexity of regulatory mechanisms distal to the events that allow intracellular calcium mobilization. Thus for the first time, it has been possible to study ordered events of T cell activation in non-transformed, antigen-dependent human T lymphocytes. The data presented in this paper suggest that T cell activation is not an all or nothing phenomenon, and there is an ordered sequence of events that can be differentiated based upon signal requirements at the T cell membrane.

Ligand-receptor interactions required for commitment to the activation of the interleukin 2 gene

Concanavalin A (Con A), which together with phorbol myristate acetate (PMA) can activate the human T cell line Jurkat to produce interleukin 2 (IL 2), is shown to depend on the expression of the T3/T cell antigen receptor heterodimer (T3/Ti) complex to induce activation. alpha-methyl mannoside was able to reverse all of the observed effects of Con A on intracellular biochemical events. Therefore, ligand-receptor occupancy appears to be required for sustaining biochemical events associated with triggering the T3/Ti complex. Studies of the time-dependent requirements for the two stimuli required for activation revealed that simultaneous stimulation with both Con A and PMA is required for 2 to 4 hr for the cell to commit itself to activation, as measured by the appearance of secreted IL 2. This 2- to 4-hr requirement correlated precisely with the appearance of IL 2 mRNA, and the appearance of IL 2 transcripts depended on protein synthesis during this critical time period.

Ligand-receptor interactions required for commitment to the activation of the interleukin 2 gene

Concanavalin A (Con A), which together with phorbol myristate acetate (PMA) can activate the human T cell line Jurkat to produce interleukin 2 (IL 2), is shown to depend on the expression of the T3/T cell antigen receptor heterodimer (T3/Ti) complex to induce activation. alpha-methyl mannoside was able to reverse all of the observed effects of Con A on intracellular biochemical events. Therefore, ligand-receptor occupancy appears to be required for sustaining biochemical events associated with triggering the T3/Ti complex. Studies of the time-dependent requirements for the two stimuli required for activation revealed that simultaneous stimulation with both Con A and PMA is required for 2 to 4 hr for the cell to commit itself to activation, as measured by the appearance of secreted IL 2. This 2- to 4-hr requirement correlated precisely with the appearance of IL 2 mRNA, and the appearance of IL 2 transcripts depended on protein synthesis during this critical time period.

Synergy between the T3/antigen receptor complex and Tp44 in the activation of human T cells

In addition to the T3/antigen receptor complex (T3/Ti), other T cell surface molecules participate in early events involved in human T cell activation. In this report we document that monoclonal antibody 9.3, which recognizes a 90,000 dalton homodimer expressed on human T cells, synergizes with ligands reacting with T3/Ti to activate purified T cells and Jurkat, a human T cell leukemic line. Unlike phorbol myristate acetate (PMA), 9.3 was able to synergize only with anti-T3 or anti-Ti if these antibodies were immobilized. Moreover, 9.3 failed to synergize with the calcium ionophore ionomycin. At high concentrations only, 9.3 could synergize with PMA in the activation of Jurkat and a T3/Ti negative mutant of Jurkat. At such high concentrations of 9.3, small transient increases in cytoplasmic free calcium ((Ca++)i) were detected in quin 2-loaded Jurkat cells. This increase in (Ca++)i was the result of release of internal stores of calcium. 9.3 induced the hydrolysis of polyphosphoinositides, albeit the magnitude of inositol phosphates generated in response to 9.3 was substantially less than that observed with anti-Ti. No effect on pkC translocation was observed in Jurkat cells stimulated with 9.3. Although the small increase in (Ca++)i induced by 9.3 may account for its synergy with PMA, this effect is unlikely to account for the more potent synergistic effect observed with 9.3 and phytohemagglutinin or immobilized anti-T3 and anti-Ti antibodies.

Synergy between the T3/antigen receptor complex and Tp44 in the activation of human T cells

In addition to the T3/antigen receptor complex (T3/Ti), other T cell surface molecules participate in early events involved in human T cell activation. In this report we document that monoclonal antibody 9.3, which recognizes a 90,000 dalton homodimer expressed on human T cells, synergizes with ligands reacting with T3/Ti to activate purified T cells and Jurkat, a human T cell leukemic line. Unlike phorbol myristate acetate (PMA), 9.3 was able to synergize only with anti-T3 or anti-Ti if these antibodies were immobilized. Moreover, 9.3 failed to synergize with the calcium ionophore ionomycin. At high concentrations only, 9.3 could synergize with PMA in the activation of Jurkat and a T3/Ti negative mutant of Jurkat. At such high concentrations of 9.3, small transient increases in cytoplasmic free calcium ((Ca++)i) were detected in quin 2-loaded Jurkat cells. This increase in (Ca++)i was the result of release of internal stores of calcium. 9.3 induced the hydrolysis of polyphosphoinositides, albeit the magnitude of inositol phosphates generated in response to 9.3 was substantially less than that observed with anti-Ti. No effect on pkC translocation was observed in Jurkat cells stimulated with 9.3. Although the small increase in (Ca++)i induced by 9.3 may account for its synergy with PMA, this effect is unlikely to account for the more potent synergistic effect observed with 9.3 and phytohemagglutinin or immobilized anti-T3 and anti-Ti antibodies.

The role of the T3/antigen receptor complex in T-cell activation

The role of the T3/antigen receptor complex is summarized by the diagram presented in Figure 4. Signals transmitted through T3/Ti activate a phosphodiesterase. This enzyme acts on its substrate PIP2 to generate two important mediators, IP3 and diacylglycerol. IP3 mobilizes calcium from bound intracellular stones. This increase in [Ca2+]i is one intracellular signal which, in conjunction with others, induces expression of lymphokine genes by influencing pretranslational, presumably transcriptional, events. Several problems remain. Which of the five molecules in the T3/Ti complex serves as the effector molecule in the transmembrane signaling process is not known. Which molecules serve to link T3/Ti to the phosphodiesterase enzyme is under investigation. The role diacylglycerol protein kinase C and other mediators play in signalling activation is not established. Finally, for those events occurring after the early events pictured in Figure 4 that result in gene activation, the sequence is a black box. Approaches to address each of these questions are available, and answers should be forthcoming.

Activation of a human T cell line: a two-stimulus requirement in the pretranslational events involved in the coordinate expression of interleukin 2 and gamma-interferon genes

In the resting state, the T3-positive, human T cell line Jurkat does not synthesize detectable amounts of either interleukin 2 (IL 2) or gamma-interferon (IFN-gamma). Activation of Jurkat as measured by the secretion of substantial amounts of both lymphokines requires two distinct signals. One signal is produced by the phorbol ester, phorbol myristate acetate, and the other by either phytohemagglutinin or antibodies to T3. To elucidate the molecular events by which these activation signals lead to the synthesis of IL 2 and IFN-gamma activity we used cDNA probes to follow the appearance of IL 2 and IFN-gamma-specific transcripts after activation of Jurkat. These studies demonstrate that both signals are required for the appearance of IL 2 or IFN-gamma-specific transcripts and that the appearance of IL 2 and IFN-gamma RNA is coordinate with regard to a) the signals required for their production, b) the kinetics of their appearance, and c) the inhibition of their appearance by cyclosporin A. These studies suggest that distinct T cell-activation signals may operate through a common regulatory pathway involved in the expression of both IL 2 and IFN-gamma genes.

Activation of a human T cell line: a two-stimulus requirement in the pretranslational events involved in the coordinate expression of interleukin 2 and gamma-interferon genes

In the resting state, the T3-positive, human T cell line Jurkat does not synthesize detectable amounts of either interleukin 2 (IL 2) or gamma-interferon (IFN-gamma). Activation of Jurkat as measured by the secretion of substantial amounts of both lymphokines requires two distinct signals. One signal is produced by the phorbol ester, phorbol myristate acetate, and the other by either phytohemagglutinin or antibodies to T3. To elucidate the molecular events by which these activation signals lead to the synthesis of IL 2 and IFN-gamma activity we used cDNA probes to follow the appearance of IL 2 and IFN-gamma-specific transcripts after activation of Jurkat. These studies demonstrate that both signals are required for the appearance of IL 2 or IFN-gamma-specific transcripts and that the appearance of IL 2 and IFN-gamma RNA is coordinate with regard to a) the signals required for their production, b) the kinetics of their appearance, and c) the inhibition of their appearance by cyclosporin A. These studies suggest that distinct T cell-activation signals may operate through a common regulatory pathway involved in the expression of both IL 2 and IFN-gamma genes.

Role of T3 surface molecules in human T-cell activation: T3-dependent activation results in an increase in cytoplasmic free calcium

The human T-cell leukemia, Jurkat, and a T3-negative mutant of Jurkat (S.5) were used to study the role of T3 in human T-cell activation. Incubation of Jurkat with phytohemagglutinin (PHA) resulted in the production of interleukin 2, which was markedly increased by the addition of phorbol 12-myristate 13-acetate (PMA). Antibodies reactive with T3 could activate Jurkat only if added together with PMA. However, S.5 cells failed to produce interleukin 2 in response to PHA and produced 1/16th the interleukin 2 activity that Jurkat produced in response to PHA and PMA. Incubation of S.5 cells with the calcium ionophore A23187 and PMA resulted in the production of interleukin 2 activity comparable to that produced by Jurkat. Like antibodies reactive with T3, A23187 demonstrated an obligate requirement for PMA in order to activate Jurkat or S.5. These observations suggested that T3 might participate in T-cell activation through mechanisms that increase intracellular Ca2+. This was examined by using the Ca2+ sensitive fluor, quin-2, to measure levels of cytoplasmic free Ca2+ [( Ca2+]i). Addition of PHA, A23187, or monoclonal antibodies reactive with T3 to Jurkat cells resulted in substantial increases of [Ca2+]i. In contrast, only A23187 could induce an increase in [Ca2+]i in S.5 cells. Three other monoclonal antibodies reactive with other membrane antigens expressed on Jurkat or S.5 did not increase [Ca2+]i. These results suggest that T3 and/or associated molecules participate in T-cell activation through mechanisms that lead to increases in [Ca2+]i and that their expression is a relative requirement for T-cell activation by PHA.