Intraepithelial Lymphogram in the Diagnosis of Celiac Disease in Adult Patients: A Validation Cohort

BACKGROUND

Celiac disease is a gluten-related pathology, highly prevalent and heterogeneous in its clinical presentation, which leads to delays in diagnosis and misdiagnosis. The analysis of duodenal intraepithelial lymphocytes (IELs) by flow cytometry (lymphogram) is emerging as a discriminative tool in the diagnosis of various forms of celiac disease (CD).

AIMS

The aim of this study was to validate IEL lymphogram performance in the largest adult series to our knowledge, in support of its use as a diagnostic tool and as a biomarker of the dynamic celiac process.

METHODS

This was a retrospective study including 768 adult patients (217 with active CD, 195 on a gluten-free diet, 15 potential CD patients, and 411 non-celiac controls). The IEL subset cut-off values were established to calculate the diagnostic accuracy of the lymphogram.

RESULTS

A complete celiac lymphogram profile (≥14% increase in T cell receptor [TCR]γδ IELs and simultaneous ≤4% decrease in surface-negative CD3 [sCD3-] IELs) was strongly associated with active and potential forms in over 80% of the confirmed patients with CD, whereas the remaining patients with CD had partial lymphogram profiles (≥14% increase in TCRγδ or ≤4% decrease in sCD3- IELs), with lower diagnostic certainty. None of these patients had a non-celiac lymphogram. Quantifying the TCRγδ versus sCD3- imbalance as a ratio (≥5) is a discriminative index to discard or suspect CD at diagnosis.

CONCLUSIONS

We have validated the IEL lymphogram's diagnostic efficiency (79% sensitivity, 98% specificity), with an LR+ accuracy of 36.2. As expected, the increase in TCRγδ IELs is a reliable marker for celiac enteropathy, while changes in sCD3- IEL levels throughout the dynamic CD process are useful biomarkers of mucosal lesions.

Intestinal and blood lymphograms as new diagnostic tests for celiac disease

Accurate celiac disease (CD) diagnosis is still challenging for some specific patients or circumstances. Thus, much effort has been expended last decades focused on seronegative or low grade enteropathy CD and, especially, on enable early diagnosis of individuals on a gluten-free diet (GFD). We discuss here two diagnostic approaches based on immunophenotyping by flow cytometry that we expect to reduce the persistent low diagnostic rates and the common diagnostic delay. The intraepithelial lymphogram is based on determining the percentage of TCRγδ+ and surface CD3- lymphocytes in the intestinal epithelium. The concomitant increase in TCRγδ+ and decrease in surface CD3- intraepithelial lymphocytes has been termed the celiac lymphogram and has been proved to be discriminative in seronegative, low grade enteropathy and potential CD, as well as in most CD patients on a GFD. A blood lymphogram based on the analysis of activated gut-homing CD8+ T cells combined with a 3-day gluten challenge is also considered, which has shown high sensitivity and specificity to diagnose seropositive Marsh 1 and Marsh 3 CD in individuals following a GFD. In addition, flow cytometry can be extremely useful in cases of refractory CD type II to identify aberrant cells. Those approaches represent highly accurate methods for CD diagnosis, being simple, fast, highly reproducible and of easy implementation in clinical practice.

Assessment of Duodenal Intraepithelial Lymphocyte Composition (Lymphogram) for Accurate and Prompt Diagnosis of Celiac Disease in Pediatric Patients

INTRODUCTION

Quantitative and phenotypic analyses of duodenal intraepithelial lymphocytes (IELs) by flow cytometry (IEL lymphogram) confer specificity and enable the diagnosis even in unconventional presentations of celiac disease (CD). To evaluate the validity of the IEL lymphograms in the pediatric population for new insights into their use as biomarkers in the natural history of CD.

METHODS

We retrospectively included 1,211 children (602 with active CD, 92 on a gluten-free diet, 47 with potential CD, and 470 nonceliac controls) who required duodenal biopsies in this study. The cutoff values for IEL subsets were established to calculate the probability of disease according to the lymphogram.

RESULTS

A celiac lymphogram (a ≥15% increase in gamma-delta T-cell receptor IELs and a simultaneous ≤6% decrease in CD3 surface-negative [sCD3-]) IELs was strongly associated with the diagnosis of active CD, which was present in 89.7% of the confirmed patients. The remaining 10% of the celiac patients had a partial celiac lymphogram (≥15% increase gamma-delta T-cell receptor IELs or ≤6% decrease in sCD3- IELs), with lower diagnostic certainty. On a gluten-free diet, nearly 20% of the patients were indistinguishable from nonceliac subjects based on the lymphogram. In potential CD, a decrease in sCD3- IELs was a risk marker of progression to villous atrophy and a diagnosis of active CD.

DISCUSSION

If a biopsy is clinically indicated, the IEL lymphogram adds specificity to the histological findings, reducing diagnostic delays and misdiagnoses. The lymphogram is useful for monitoring the natural progression of the disease and predicting the transition from potential celiac to overt CD.

Remission Induced by TNF Inhibitors Plus Methotrexate is Associated With Changes in Peripheral Naïve B Cells in Patients With Rheumatoid Arthritis

Biological therapies, such as TNF inhibitors (TNFi), are increasing remission (REM) rates in rheumatoid arthritis (RA) patients, although these are still limited. The aim of our study was to analyze changes in the profile of peripheral blood mononuclear cells (PBMC) in patients with RA treated with TNFi in relation to the clinical response. This is a prospective and observational study including 78 RA patients starting the first TNFi. PBMC were analyzed by flow cytometry both at baseline and at 6 months. Disease activity at the same time points was assessed by DAS28, establishing DAS28 ≤ 2.6 as the criteria for REM. Logistic regression models were employed to analyze the association between the changes in PBMC and REM. After 6 months of TNFi treatment, 37% patients achieved REM by DAS28. Patients who achieved REM showed a reduction in the percentage of naive B cells, but only when patients had received concomitant methotrexate (MTX) (OR: 0.59; 95% CI: 0.39–0.91). However, no association was found for patients who did not receive concomitant MTX (OR: 0.85; 95% CI: 0.63–1.16). In conclusion, PBMC, mainly the B-cell subsets, are modified in RA patients with TNFi who achieve clinical REM. A significant decrease in naive B-cell percentage is associated with achieving REM after 6 months of TNFi treatment in patients who received concomitant therapy with MTX.

An Immunologic Compatibility Testing Was Not Useful for Donor Selection in Fecal Microbiota Transplantation for Ulcerative Colitis

Fecal microbiota transplantation (FMT) is an effective procedure against Clostridioides difficile infection (CDI), with promising but still suboptimal performance in other diseases, such as ulcerative colitis (UC). The recipient’s mucosal immune response against the donor’s microbiota could be relevant factor in the effectiveness of FMT. Our aim was to design and validate an individualized immune-based test to optimize the fecal donor selection for FMT. First, we performed an in vitro validation of the test by co-culturing lymphocytes obtained from the small intestine mucosa of organ donor cadavers (n=7) and microbe-associated molecular patterns (MAMPs) obtained from the feces of 19 healthy donors. The inflammatory response was determined by interleukin supernatant quantification using the Cytometric Bead Array kit (B&D). We then conducted a clinical pilot study with 4 patients with UC using immunocompetent cells extracted from rectal biopsies and MAMPs from 3 donor candidates. We employed the test results to guide donor selection for FMT, which was performed by colonoscopy followed by 4 booster instillations by enema in the following month. The microbiome engraftment was assessed by 16S rDNA massive sequencing in feces, and the patients were clinically followed-up for 16 weeks. The results demonstrated that IL-6, IL-8, and IL-1ß were the most variable markers, although we observed a general tolerance to the microbial insults. Clinical and colonoscopy remission of the patients with UC was not achieved after 16 weeks, although FMT provoked enrichment of the Bacteroidota phylum and Prevotella genus, with a decrease in the Actinobacteriota phylum and Agathobacter genus. The most relevant result was the lack of Akkermansia engraftment in UC. In summary, the clinical success of FMT in patients with UC appears not to be influenced by donor selection based on the explored recipient’s local immunological response to FMT, suggesting that this approach would not be valid for FMT fecal donor optimization in such patients.

POS0623 CYTOKINE PRODUCTION BY BLOOD LYMPHOCYTES DEFINES A PROFILE ASSOCIATED WITH NON-REMISSION IN PATIENTS WITH RHEUMATOID ARTHRITIS TREATED WITH TNF INHIBITORS

Background:

In clinical practice no more than 50% of the patients treated with TNF inhibitors (TNFi) achieve remission (REM). Previous investigations suggested that peripheral blood mononuclear cells (PBMC) may be markers associated with the TNFi treatment success1.

Objectives:

This study aims to analyse the intracellular cytokine production by PBMC and its association with REM achievement after 6 months (m) of TNFi treatment in patients with RA.

Methods:

This was a prospective study including 62 patients with RA starting the 1st TNFi. PBMC were isolated from patients at baseline and after 6m of treatment with TNFi and cryopreserved until studied. In vitro stimulation and intracellular cytokine production by PBMC was performed as follow: in the presence of 2µg/mL brefeldin and 2µmol/L monensin monocytes were stimulated with 20ng/mL LPS during 4h whereas lymphocytes were stimulated with 50ng/mL phorbol 12-myristate 13-acetate and 750ng/mL ionomycin for 4h at 37°C. To identify IL10-producing B cells, PBMC were pre-incubated with 3µg/mL of CpG oligonucleotide during 20h at 37°C prior to stimulation. Intracellular cytokine production (TNFα, IL6, GM-CSF, IL10) by the different cell subsets (monocytes, CD4+ and CD8+ T cells, naïve and memory B cells) was analysed by flow-cytometry. Clinical activity at baseline and after 6m was assessed by DAS28-ESR. REM was defined as DAS28≤2.6 at 6m. The association between cytokine production by each PBMC subset and REM was analysed through univariable and multivariable logistic regression models. Receiving operating curve (ROC) analysis was used to select the optimal ratio of cytokine production associated with REM status.

Results:

After 6m of TNFi treatment, 30 (48%) patients achieved REM. No significant differences between REM and non-REM groups were observed for patients’ characteristics at baseline except for DAS28, which was lower in the REM group (non-REM: 5.4±0.9; REM: 4.3±0.9; p<0.0001) (Table 1). Therefore, further analyses were adjusted by baseline DAS28. A lower ratio between calculated with the IL10 and TNFα production by B cells and by CD4+ T cells (IL10 B/TNF CD4) at 6m was found for non-REM patients (non-REM: 0.31 vs REM: 0.54; p=0.007). Based on a ROC analysis, we found that a (IL10 B/TNF CD4)<0.54 at 6 m was significantly associated with a higher probability of non-REM at 6 months (OR: 5.0; 95% CI: 1.1-21.7) (Figure 1).

Table 1.

Baseline predictors of reduction of disease activity at 12 months from start of abatacept. Linear regression.

Baseline patients’ characteristicsTotal patients (n=62)DAS28>2.6(n=32; 52%)DAS28≤2.6(n=30; 48%)p-valueAge (years)53±1253±1352±100.8Female55 (89)30 (94)25 (83)0.2Disease duration (years)8 (4-11)8 (4-12)7 (3-11)0.7RF positive49 (79)23 (72)26 (87)0.1ACPA positive54 (87)26 (81)28 (93)0.2Smoking habit (n=55)0.2Non-smokers26 (47)16 (55)10 (38) Smoker29 (53)13 (45)16 (51)Body mass index (kg/m2)25.9±5.625.8±5.726.0±5.60.9DAS284.9±1.05.4±0.94.3±0.9<0.0001Concomitant csDMARDs60 (97)32 (100)28 (93)0.3MTX [±OD]46 (74)26 (81)20 (67)0.3Only OD14 (23)6 (19)8 (26)0.3Prednisone36 (58)19 (59)17 (57)0.9

Conclusion:

Our results show that the proinflammatory IL10 B/TNF CD4 ratio is associated with non-REM status. It could be useful to analyse the success of TNFi treatment in patients with RA.

References:

[1]Rodríguez-Martín E, et al. Front Immunol. 2020; 11: 1913.

Acknowledgements:

ISCIII (PI16/00474; PI16/01092)

Disclosure of Interests:

Borja Hernández-Breijo: None declared, Eulalia Rodríguez-Martín: None declared, Carlota García-Hoz: None declared, Victoria Navarro-Compán Speakers bureau: Abbvie, Janssen, Lilly, MSD, Novartis, Pfizer and UCB, Grant/research support from: Abbvie, Janssen, Lilly, MSD, Novartis, Pfizer and UCB, Cristina Sobrino: None declared, ANA MARTÍNEZ-FEITO: None declared, Israel Nieto-Gañán: None declared, Javier Bachiller-Corral Speakers bureau: Abbvie, MSD, BMS and Roche, Grant/research support from: Pfizer, Paloma Lapuente-Suanzes: None declared, Gemma Bonilla: None declared, Cristina Pijoán-Moratalla: None declared, Mónica Vázquez: None declared, Alejandro Balsa Speakers bureau: Abbvie, BMS, Nordic, Novartis, Pfizer, Sandoz, Sanofi, Roche and UCB, DORA PASCUAL-SALCEDO: None declared, Luisa María Villar: None declared, Chamaida Plasencia Speakers bureau: AbbVie, Lilly, Novartis, Pfizer, Sanofi, Biogen and UCB

Blood Lymphocyte Subsets for Early Identification of Non-Remission to TNF Inhibitors in Rheumatoid Arthritis

Background: TNF inhibitors (TNFis) are widely used for the treatment of rheumatoid arthritis (RA), although the response rates to this therapy in patients with RA remains heterogeneous and < 50% achieve remission (REM). Objective: To analyze baseline peripheral blood leukocytes profiles in order to search for biomarkers identifying patients who will most likely not achieve REM under TNFi treatment. Methods: A prospective bi-center pilot study including 98 RA patients treated with TNFis and followed-up during 6 months. Patients were classified according to DAS28 as follows: those who achieved REM (DAS28 ≤ 2.6) and those who did not (DAS28 > 2.6) at 6 months after starting TNFis. These rates were also assessed by simplified disease activity index (SDAI ≤ 3.3 and SDAI > 3.3, respectively). Peripheral blood immune cells were studied by flow cytometry before treatment initiation. Results: At 6 months, 61 or 80% of patients did not achieve REM by DAS28 or SDAI, respectively. Basal leukocyte profiles differed between REM vs. non-REM patients. Non-REM patients showed lower percentages of total and naïve B cells at baseline than REM subjects. A B lymphocyte/CD4+ lymphocyte ratio (BL/CD4 ratio) <0.2 clearly associated with a higher probability of non-REM status based on DAS28 at 6 months (OR = 9.2, p = 0.006). These data were confirmed when patient response was evaluated by SDAI index. Conclusion: Our results strongly suggest that BL/CD4 ratio could be considered as a useful biomarker for the early identification of non-remitters to TNFi in clinical practice.

FRI0250 “ARE MYOSITIS ANTIBODIES SPECIFIC FOR IDIOPATHIC INFLAMMATORY MYOPATHY DIAGNOSIS?” CLINICAL CORRELATION OF A COHORT OF PATIENTS POSITIVE FOR MYOSITIS ANTIBODIES

Background:

Idiopathic inflammatory myopathies (IIM) are a group of immune-mediated diseases characterized my muscle weakness, skin rash and systemic involvement. Myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) play a major role in IIM diagnosis, classification and prognosis. Nevertheless, MSA/MAA testing is not standardized and there very few studies addressing their relationship with other diseases.

Objectives:

To describe a cohort of patients tested positive for MSA/MAA, and to explore it´s relationship with IIM and other autoimmune diseases.

Methods:

We retrospectively review all the serum samples obtained from patients tested for MSA/MAA during 2019 in the Immunology department of Ramón y Cajal University Hospital (Madrid, Spain). These antibodies were tested by specific immunoblot (EUROLINE: Autoimmune Inflammatory Myopathies 16 Ag) with highly purified MSA/MAA. Positivity was stablished according to absorbance titer and adjusted by positive control of each test (arbitrary units, AU). Patients were diagnosed with IIM according to their clinician diagnosis. Diagnosis and classification were confirmed by an independent rheumatologist (JL) according to current understanding of IIM classification.

Results:

Three-hundred-seventy-five samples were tested for MSA during the study period. Two-hundred-seventy-nine were negative for all antibodies tested. Ninety-six samples were positive for one or more MSA/MAA, corresponding to 74 patients (11 patients had 2 different samples). Forty-nine (66.2%) of the patients who tested positive were female and 25 (33.8%) were male. Mean age was 58.65 years. Only 22 patients (29.7%) had a confirmed diagnosis of IIM, 24 (32.4%) had a diagnosis of other autoimmune disease, and 11 (14.9%) were diagnosed with interstitial lung disease (ILD) (Figure 1). Six ILD patients had anti-PM-Scl or anti-Ku antibodies, which are associated with scleroderma or overlap-CTD myositis, nevertheless, they remained classified as ILD as no other features were described in this group.

Seventeen patients were positive for more than 1 MAA or MSA, including 14 patients positive for anti Ro-52. Antibody titer was higher in the IIM group compared to non-myositis group (59.59 vs 44.16, p=0.015). Anti Mi-2 was positive in 4 ILD without any other myositis features, and high titer anti-SRP (n=4, mean 59.75 AU) was found in primary biliary cirrhosis (PBC) patients. Additionally, 5 patients positive for antiJo-1 using ELIA (Thermo Fisher) were diagnosed with antisynthetase syndrome. IIM diagnosis and its relationship with antibody titer is represented in table 1.

Table 1.

Autoantibody titer according to diagnosis.

Antibody (Number of patients)Number of samplesIIMIIM antibody titer (AU)Non-IIMNon-IIM antibody titer (AU)Other AI diseasesAnti Ro-52Anti Jo-1 (n=1)11 (100%)92.70-01 (100%)Anti PL-7 (n=8)113 (37.5%)29.595 (62.5%)25.595 (62.5%)2 (25%)Anti PL-12 (n=3)21 (33.3%)53.952 (66.6%)69.971 (33.3%)2 (50%)Anti EJ (n=1)11 (100%)99.460-01 (100%)Anti OJ (n=2)40-2 (100%)23.041 (50%)0Anti Ku (n=14)193 (21.4%)107.2511 (78.6%)31.855 (35.7%)0Anti Tif1gamma (n=5)63 (60%)40.122 (40%)23.841 (20%)0Anti NXP2 (n=2)30-2 (100%)13.991 (50%)1 (50%)Anti Mi2 (n=12)173 (25%)48.659 (75%)26.674 (33.3%)0Anti SAE (n=1)10-1 (100%)1800Anti MDA5 (n=2)32 (100%)30.5401 (50%)1 (50%)Anti SRP (n=9)124 (44.4%)42.695 (55.6%)68.165 (55.5%)2 (22.2%)Anti PM-Scl75 and PM-Scl100 (n=2)21 (50%)68.61 (50%)36.6700Anti PM-Scl75 (n=8)10016.268 (100%)22.723 (37.5%)1 (12.5%)Anti PM-Scl100 (n=4)50-4 (100%)23.622 (50%)0

Conclusion:

Only 28.7% of the patients that were MAA/MSA positive had a diagnosis of IIM. Other autoimmune diseases and ILD were commonly found in this group of MSA/MAA positive patients.

References:

[1]Damoiseaux J, Vulsteke JB, Tseng CW, Platteel ACM, Piette Y, Shovman O, et al. Autoantibodies in idiopathic inflammatory myopathies: Clinical associations and laboratory evaluation by mono- and multispecific immunoassays. Vol. 18, Autoimmunity Reviews. Elsevier B.V.; 2019. p. 293–305.

Disclosure of Interests:

None declared

FRI0582 GM-CSF PRODUCED BY CD4+ T CELLS AS A MARKER OF CLINICAL REMISSION IN PATIENTS WITH RHEUMATOID ARTHRITIS TREATED WITH TNF INHIBITORS

Background:

According to the EULAR recommendations, the therapeutic target in patients with RA should be remission (REM). However, no more than 50% of the patients treated with TNF inhibitors (TNFi) attains this outcome. Previous investigations suggested the peripheral blood mononuclear cells (PBMC) as markers associated with the TNFi treatment success1,2. Granulocyte-monocyte colony-stimulating factor (GM-CSF) plays a relevant role in the pathogenesis of rheumatoid arthritis (RA) because it promotes the macrophage differentiation, survival and activation3.

Objectives:

To analyse the intracellular cytokine production by PBMC and its association with REM attainment after 6 months (m) of TNFi treatment in patients with RA.

Methods:

This was a prospective bi-center pilot study including 36 patients with RA. PBMC were isolated from patients at baseline and after 6m of treatment with TNFi and cryopreserved until studied. Intracellular cytokine production by PBMC was stimulated in the presence of 2µg/mL brefeldin as follow: monocytes were stimulated with 20ng/mL LPS during 4h; and simultaneously lymphocytes were stimulated with 50ng/mL phorbol 12-myristate 13-acetate (PMA) and 750ng/mL ionomycin during 4h at 37°C. To identify IL-10-producing B cells, PBMC were pre-incubated with 3µg/mL of CpG oligonucleotide during 20h at 37°C prior to stimulation in presence of 2µmol/L monensin. Intracellular cytokine production (TNFα, IL6, GM-CSF, IL10) by the different cell subsets (monocytes, CD4+and CD8+T cells, naïve and memory B cells) was analysed by flow-cytometry. Clinical activity at baseline and after 6m was assessed by DAS28. REM was defined as DAS28≤2.6 at 6m. The association between REM and the change in cytokine production (Δ, 6m-0m) by each PBMC subset was analysed through univariable and multivariable logistic regression models.

Results:

Seventy-eight percent of the patients were female. After 6m of TNFi treatment, 47% patients attained REM. Univariable analyses was performed to investigate the association between REM and the baseline variables. Male sex (OR: 12.6; 95% CI: 1.35-117.57; p=0.03) and having lower baseline DAS28 (OR: 0.4; 95% CI: 0.19-0.85; p=0.02) were independently associated with attaining REM after 6m of TNFi. In the multivariable analysis, only being male (OR: 19.7; 95% CI: 1.4-273.9; p=0.03) remained independently associated with REM after 6m of treatment. Therefore, further analyses were adjusted by sex. Decreased production of GM-CSF by CD4+T cells percentage was found after 6m of TNFi treatment in REM patients (0m: 6.07%; 6m: 3.87%; p=0.007) while no-REM patients did not show differences with the baseline (0m: 3.70%; 6m: 3.75%; p=0.9). The decrease was significantly associated with attaining REM (OR: 0.56; 95% CI: 0.33-0.95; p: 0.03). No significant association was found between any other analysed intracellular cytokine produced by the different PBMC subsets and REM.

Conclusion:

GM-CSF intracellular production by CD4+T cells was significantly decreased by TNFi treatment only in patients who attained REM. Therefore, our results suggest that GM-CSF production by CD4+T cells may be a useful marker of REM to TNFi in RA.

References:

[1] Sobrino C, et al. Ann Rheum Dis. 2019; 78 (S2): A1665.

[2] Hernández-Breijo B, et al. Ann Rheum Dis. 2019; 78 (S2): A711.

[3] Avci AB, et al. Clin Exp Rheumatol. 2016; 34 (S98), 39-44.

Figure. 1:

Association between the change in intracellular cytokine production (Δ, 6m-0m) by each PBMC subset and REM. Adjusted logistic regression analyses were performed for each cytokine.

Acknowledgments:

ISCIII (PI16/00474; PI16/01092)

Disclosure of Interests:

Borja Hernández-Breijo: None declared, Chamaida Plasencia: None declared, Carlota García-Hoz: None declared, Cristina Sobrino: None declared, Victoria Navarro-Compán Consultant of: Abbvie, Lilly, Novartis, Pfizer, UCB, Speakers bureau: AbbVie, MSD, Lilly, Novartis, Pfizer, UCB, ANA MARTÍNEZ-FEITO: None declared, Israel Nieto-Gañán: None declared, Paloma Lapuente-Suanzes: None declared, Javier Bachiller-Corral: None declared, Gemma Bonilla: None declared, Cristina Pijoan Moratalla: None declared, Garbiñe Roy: None declared, Mónica Vázquez Díaz: None declared, Alejandro Balsa Grant/research support from: BMS, Roche, Consultant of: AbbVie, Gilead, Lilly, Pfizer, UCB, Sanofi, Sandoz, Speakers bureau: AbbVie, Lilly, Sanofi, Novartis, Pfizer, UCB, Roche, Nordic, Sandoz, Luisa María Villar: None declared, DORA PASCUAL-SALCEDO Grant/research support from: Pfizer, Novartis & Progenika, Speakers bureau: Pfizer, Merck, Novartis, Takeda, Menarini & Grifols, Eulalia Rodríguez-Martín: None declared

The Intracellular Intensity of CD3 on Aberrant Intraepithelial Lymphocytes Is a Prognostic Factor of the Progression to Overt Lymphoma in Refractory Celiac Disease Type II (Pre-Enteropathy-Associated T Cell Lymphoma)

BACKGROUND

Refractory celiac disease type II (RCD-II) is a very rare yet severe complication of celiac disease (CD) with a 50% rate of progression to Enteropathy-associated T-cell lymphoma (EATL). Timely diagnosis and treatment of RCD-II is of the essence and requires the identification of a population of frequently clonal, phenotypically aberrant intraepithelial lymphocytes (IELs). Flow Cytometry of intestinal IELs is the recommended method to identify the aberrant surface CD3-negative (sCD3-) intracytoplasmic CD3-positive (icCD3ε+) IELs, and a proportion of >20% is diagnostic of RCD-II. There is substantial heterogeneity in the clinical course of RCD-II, and insufficient information on prognostic factors.

AIM

To establish flow cytometric predictors of the clinical evolution of RCD-II, to help guide treatment approaches.

PATIENTS AND METHODS

Retrospective single-center study of clinical and immunological features of 6 RCD-II patients and a control group, both identified from a 2,000-patient cohort over 16 years. IEL subset frequencies and the intensity of staining for surface (s) and intracytoplasmic (ic) CD3ε+ on IEL subsets were quantified and correlated with the clinical outcome.

RESULTS

Unexpectedly, the frequency of aberrant sCD3- icCD3ε+ cells at diagnosis did not correlate with histological or clinical affection. However, a higher intensity of icCD3ε+ staining in the aberrant IELs relative to expression on normal IELs correlated with monoclonality and with worse clinical outcomes.

CONCLUSION

The ratio of icCD3ε+ on aberrant IELs vs. normal IELs appears to be a useful indicator of prognosis at the time of diagnosis, and may represent a novel tool in the follow-up of RCD-II patients after therapy.

Protein Kinase C ζ Interacts with a Novel Binding Region of Gαq to Act as a Functional Effector

Heterotrimeric G proteins play an essential role in the initiation of G protein-coupled receptor (GPCR) signaling through specific interactions with a variety of cellular effectors. We have recently reported that GPCR activation promotes a direct interaction between Gαq and protein kinase C ζ (PKCζ), leading to the stimulation of the ERK5 pathway independent of the canonical effector PLCβ. We report herein that the activation-dependent Gαq/PKCζ complex involves the basic PB1-type II domain of PKCζ and a novel interaction module in Gαq different from the classical effector-binding site. Point mutations in this Gαq region completely abrogate ERK5 phosphorylation, indicating that Gαq/PKCζ association is required for the activation of the pathway. Indeed, PKCζ was demonstrated to directly bind ERK5 thus acting as a scaffold between Gαq and ERK5 upon GPCR activation. The inhibition of these protein complexes by G protein-coupled receptor kinase 2, a known Gαq modulator, led to a complete abrogation of ERK5 stimulation. Finally, we reveal that Gαq/PKCζ complexes link Gαq to apoptotic cell death pathways. Our data suggest that the interaction between this novel region in Gαq and the effector PKCζ is a key event in Gαq signaling.

Gαq signalling: the new and the old

In the last few years the interactome of Gαq has expanded considerably, contributing to improve our understanding of the cellular and physiological events controlled by this G alpha subunit. The availability of high-resolution crystal structures has led the identification of an effector-binding region within the surface of Gαq that is able to recognise a variety of effector proteins. Consequently, it has been possible to ascribe different Gαq functions to specific cellular players and to identify important processes that are triggered independently of the canonical activation of phospholipase Cβ (PLCβ), the first identified Gαq effector. Novel effectors include p63RhoGEF, that provides a link between G protein-coupled receptors and RhoA activation, phosphatidylinositol 3-kinase (PI3K), implicated in the regulation of the Akt pathway, or the cold-activated TRPM8 channel, which is directly inhibited upon Gαq binding. Recently, the activation of ERK5 MAPK by Gq-coupled receptors has also been described as a novel PLCβ-independent signalling axis that relies upon the interaction between this G protein and two novel effectors (PKCζ and MEK5). Additionally, the association of Gαq with different regulatory proteins can modulate its effector coupling ability and, therefore, its signalling potential. Regulators include accessory proteins that facilitate effector activation or, alternatively, inhibitory proteins that downregulate effector binding or promote signal termination. Moreover, Gαq is known to interact with several components of the cytoskeleton as well as with important organisers of membrane microdomains, which suggests that efficient signalling complexes might be confined to specific subcellular environments. Overall, the complex interaction network of Gαq underlies an ever-expanding functional diversity that puts forward this G alpha subunit as a major player in the control of physiological functions and in the development of different pathological situations.

ERK5 activation by Gq-coupled muscarinic receptors is independent of receptor internalization and β-arrestin recruitment

G-protein-coupled receptors (GPCRs) are known to activate both G protein- and β-arrestin-dependent signalling cascades. The initiation of mitogen-activated protein kinase (MAPK) pathways is a key downstream event in the control of cellular functions including proliferation, differentiation, migration and apoptosis. Both G proteins and β-arrestins have been reported to mediate context-specific activation of ERK1/2, p38 and JNK MAPKs. Recently, the activation of ERK5 MAPK by Gq-coupled receptors has been described to involve a direct interaction between Gαq and two novel effectors, PKCζ and MEK5. However, the possible contribution of β-arrestin towards this pathway has not yet been addressed. In the present work we sought to investigate the role of receptor internalization processes and β-arrestin recruitment in the activation of ERK5 by Gq-coupled GPCRs. Our results show that ERK5 activation is independent of M1 or M3 muscarinic receptor internalization. Furthermore, we demonstrate that phosphorylation-deficient muscarinic M1 and M3 receptors are still able to fully activate the ERK5 pathway, despite their reported inability to recruit β-arrestins. Indeed, the overexpression of Gαq, but not that of β-arrestin1 or β-arrestin2, was found to potently enhance ERK5 activation by GPCRs, whereas silencing of β-arrestin2 expression did not affect the activation of this pathway. Finally, we show that a β-arrestin-biased mutant form of angiotensin II (SII; Sar1-Ile4-Ile8 AngII) failed to promote ERK5 phosphorylation in primary cardiac fibroblasts, as compared to the natural ligand. Overall, this study shows that the activation of ERK5 MAPK by model Gq-coupled GPCRs does not depend on receptor internalization, β-arrestin recruitment or receptor phosphorylation but rather is dependent on Gαq-signalling.

Protein kinase C (PKC)ζ-mediated Gαq stimulation of ERK5 protein pathway in cardiomyocytes and cardiac fibroblasts

Gq-coupled G protein-coupled receptors (GPCRs) mediate the actions of a variety of messengers that are key regulators of cardiovascular function. Enhanced Gα(q)-mediated signaling plays an important role in cardiac hypertrophy and in the transition to heart failure. We have recently described that Gα(q) acts as an adaptor protein that facilitates PKCζ-mediated activation of ERK5 in epithelial cells. Because the ERK5 cascade is known to be involved in cardiac hypertrophy, we have investigated the potential relevance of this pathway in cardiovascular Gq-dependent signaling using both cultured cardiac cell types and chronic administration of angiotensin II in mice. We find that PKCζ is required for the activation of the ERK5 pathway by Gq-coupled GPCR in neonatal and adult murine cardiomyocyte cultures and in cardiac fibroblasts. Stimulation of ERK5 by angiotensin II is blocked upon pharmacological inhibition or siRNA-mediated silencing of PKCζ in primary cultures of cardiac cells and in neonatal cardiomyocytes isolated from PKCζ-deficient mice. Moreover, upon chronic challenge with angiotensin II, these mice fail to promote the changes in the ERK5 pathway, in gene expression patterns, and in hypertrophic markers observed in wild-type animals. Taken together, our results show that PKCζ is essential for Gq-dependent ERK5 activation in cardiomyocytes and cardiac fibroblasts and indicate a key cardiac physiological role for the Gα(q)/PKCζ/ERK5 signaling axis.

G alpha(q) acts as an adaptor protein in protein kinase C zeta (PKCzeta)-mediated ERK5 activation by G protein-coupled receptors (GPCR)

G(q)-coupled G protein-coupled receptors (GPCR) mediate the actions of a variety of messengers that are key regulators of different cellular functions. These receptors can regulate a highly interconnected network of biochemical routes that control the activity of several members of the mitogen-activated protein kinase (MAPK) family. The ERK5 MAPK has been shown to be activated by G(q)-coupled GPCR via unknown mechanisms. We find that the atypical protein kinase C (PKCzeta), previously reported to interact with the ERK5 activator MEK5 and to be involved in epidermal growth factor-mediated ERK5 stimulation, plays a crucial role in the activation of the ERK5 pathway by G(q)-coupled GPCR. Stimulation of ERK5 by G(q)-coupled GPCR is abolished upon pharmacological inhibition of PKCzeta as well as in embryonic fibroblasts obtained from PKCzeta-deficient mice. Both PKCzeta and MEK5 associate to G alpha(q) upon activation of GPCR, thus forming a ternary complex that seems essential for the activation of ERK5. These data put forward a novel function of G alpha(q) as a scaffold protein involved in the modulation of the ERK5 cascade by GPCR that could be relevant in G(q)-mediated physiological functions.

The G protein-coupled receptor kinase (GRK) interactome: role of GRKs in GPCR regulation and signaling

G protein-coupled receptor kinases (GRKs) and arrestins are key participants in the canonical pathways leading to phosphorylation-dependent GPCR desensitization, endocytosis, intracellular trafficking and resensitization as well as in the modulation of important intracellular signaling cascades by GPCR. Novel studies have revealed a phosphorylation-independent desensitization mechanism operating through their RGS-homology (RH) domain and the recent determination of the crystal structures of GRK2 and GRK6 has uncovered interesting details on the structure-function relationships of these kinases. Emerging evidence indicates that the activity of GRKs is tightly modulated by mechanisms including phosphorylation by different kinases and interaction with several cellular proteins such as calmodulin, caveolin or RKIP. In addition, GRKs are involved in multiple interactions with non-receptor proteins (PI3K, Akt, GIT or MEK) that point to novel GRK cellular roles. In this article, our purpose is to describe the ever increasing map of functional interactions for GRK proteins as a basis to better understand its contribution to cellular processes.

Tyrosine phosphorylation of G-protein-coupled-receptor kinase 2 (GRK2) by c-Src modulates its interaction with Galphaq

G-protein-coupled-receptor kinase 2 (GRK2) plays a key role in the modulation of G-protein-coupled-receptor (GPCR) signaling by both phosphorylating agonist-occupied GPCRs and by directly binding to activated Galphaq subunits, inhibiting downstream effectors activation. The GRK2/Galphaq interaction involves the N-terminal region of the kinase that displays homology to regulators of G-protein signaling (RGS) proteins. We have previously reported that upon GPCR stimulation, GRK2 can be phosphorylated by c-Src on tyrosine residues that are present in the RGS-homology (RH) region of this kinase. Here, we demonstrate that c-Src kinase activity increases the interaction between GRK2 and Galphaq. Tyrosine phosphorylation of GRK2 appears to be critically involved in the modulation of this interaction since the stimulatory effect of c-Src is not observed with a GRK2 mutant with impaired tyrosine phosphorylation (GRK2 Y13,86,92F), whereas a mutant that mimics GRK2 tyrosine phosphorylation in these residues displays an increased interaction with Galphaq. As evidence for a physiological role of this modulatory mechanism, activation of the muscarinic receptor M1, a Galphaq-coupled receptor, promotes an increase in GRK2/Galphaq co-immunoprecipitation that parallels the enhanced GRK2 phosphorylation on tyrosine residues. Moreover, c-Src activation enhances inhibition of the Galphaq/phospholipase Cbeta signaling pathway in intact cells, in a GRK2-tyrosine-phosphorylation-dependent manner. Our results suggest a feedback mechanism by which phosphorylation of GRK2 by c-Src increases both GRK2 kinase activity towards GPCRs and its specific interaction with Galphaq subunits, leading to a more rapid switch off of Galphaq-mediated signaling.