Distinct mucosal endotypes as initiators and drivers of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a potentially devastating autoimmune disease. The great majority of patients with RA are seropositive for anti-citrullinated protein antibodies (ACPAs), rheumatoid factors, or other autoantibodies. The onset of clinically apparent inflammatory arthritis meeting classification criteria (clinical RA) is preceded by ACPA seropositivity for an average of 3-5 years, a period that is designated as 'at-risk' of RA for ACPA-positive individuals who do not display signs of arthritis, or 'pre-RA' for individuals who are known to have progressed to developing clinical RA. Prior studies of individuals at-risk of RA have associated pulmonary mucosal inflammation with local production of ACPAs and rheumatoid factors, leading to development of the 'mucosal origins hypothesis'. Recent work now suggests the presence of multiple distinct mucosal site-specific mechanisms that drive RA evolution. Indicatively, subsets of individuals at-risk of RA and patients with RA harbour a faecal bacterial strain that has exhibited arthritogenic activity in animal models and that favours T helper 17 (TH17) cell responses in patients. Periodontal inflammation and oral microbiota have also been suggested to promote the development of arthritis through breaches in the mucosal barrier. Herein, we argue that mucosal sites and their associated microbial strains can contribute to RA evolution via distinct pathogenic mechanisms, which can be considered causal mucosal endotypes. Future therapies instituted for prevention in the at-risk period, or, perhaps, during clinical RA as therapeutics for active arthritis, will possibly have to address these individual mechanisms as part of precision medicine approaches.

Therapeutic interception in individuals at risk of rheumatoid arthritis to prevent clinically impactful disease.

Multiple clinical trials for rheumatoid arthritis (RA) prevention have been completed. Here, we set out to report on the lessons learnt from these studies. Researchers who conducted RA prevention trials shared the background, rationale, approach and outcomes and evaluated the lessons learnt to inform the next generation of RA prevention trials. Individuals at risk of RA can be identified through population screening, referrals to musculoskeletal programmes and by recognition of arthralgia suspicious for RA. Clinical trials in individuals at risk for future clinical RA have demonstrated that limited courses of corticosteroids, atorvastatin and hydroxychloroquine do not alter incidence rates of clinical RA; however, rituximab delays clinical RA onset, and methotrexate has transient effects in individuals who are anticitrullinated protein antibody-positive with subclinical joint inflammation identified by imaging. Abatacept delays clinical RA onset but does not fully prevent onset of RA after treatment cessation. Additionally, subclinical joint inflammation and symptoms appear responsive to interventions such as methotrexate and abatacept. To advance prevention, next steps include building networks of individuals at risk for RA, to improve risk stratification for future RA and to understand the biological mechanisms of RA development, including potential endotypes of disease, which can be targeted for prevention, thus adopting a more precision-based approach. Future trials should focus on interceptions aimed at preventing clinical RA onset and which treat existing symptoms and imaging-defined subclinical inflammation. These trials may include advanced designs (eg, adaptive) and should be combined with mechanistic studies to further define pathophysiological drivers of disease development.

The impact of the COVID-19 lockdown on social and economic welfare in Uganda.

BACKGROUND: As a measure to slow down the transmission of Coronavirus disease (COVID-19), governments around the world placed their countries under various stringent lockdown measures. Uganda is one of the countries that had a strict lockdown in Africa. This qualitative study explored the social and economic impacts of the COVID-19 lockdown in both an urban (Kampala) and rural (Wakiso) setting in Central Uganda. METHODS: The study used focus group discussions (FGDs), household interviews, and key informant interviews (KIIs). 14 FGDs were conducted among several stakeholders including community health workers, health professionals, and members of the community. 40 household interviews were conducted among low, middle, and high-income households, while 31 KIIs were held among policy makers, non-governmental organisations, and the private sector. Data were analysed thematically in NVivo 2020 (QSR International). RESULTS: Findings from the study are presented under six themes: family disruption; abuse of children's rights; disruption in education; food insecurity; impact on livelihoods; and violation of human rights. The study found that the COVID-19 lockdown led to family breakups, loss of family housing, as well as increased both caring responsibilities and gender-based violence especially towards females. Children's welfare suffered through increased child labour, sexual exploitation, and early marriages. The extended closure of schools led to delayed educational milestones, poor adaptation to home-based learning, and increased school drop-out rates. Increased food insecurity led to changes in feeding patterns and reduced food varieties. Livelihoods were negatively affected hence people depleted their savings and capital. Unlawful detention and beating by law enforcement officers increased during the lockdown. CONCLUSION: Future pandemic planning needs to consider the consequences of lockdown on the social and economic wellbeing of communities hence put in place appropriate mitigation measures during and after the outbreak.

Serum levels of B-cell activating factor are associated with a reduced risk of chronic lymphocytic leukemia.

IMPACT: Immune dysregulation is thought to contribute to chronic lymphocytic leukemia (CLL) risk, but biological mechanisms are unclear. We discovered that increased serum levels of B-cell activating factor (BAFF), an important regulator of B-cell maturation, were associated with a decreased risk of CLL, even >10 years after blood draw. Our findings suggest that BAFF could be a useful biomarker to assess risk among individuals at high risk, such as those with monoclonal b-cell lymphocytosis.

A comparison of anti-cyclic citrullinated peptides (CCP3 and CCP3.1) autoantibody tests in rheumatoid arthritis.

Background: Anti-citrullinated protein antibodies (ACPA) are a specific serological biomarker used in the diagnosis of rheumatoid arthritis (RA). In clinical practice ACPA can be identified using immunoassays targeting synthetic cyclic citrullinated peptides (CCP). The 3rd generation anti-CCP IgG antibody (CCP3) offers improved sensitivity compared to the earlier versions. Recently, CCP3.1, capable of detecting both IgG and IgA antibodies, was introduced to enhance sensitivity, especially in patients with early RA. Methods: We assessed serum CCP3.1 against CCP3 in 331 subjects undergoing RA panel serology, comprising 136 patients with RA and 195 patients without RA. Sera were tested for anti-CCP IgG (CCP3) and anti-CCP IgG/IgA (CCP3.1) antibodies. Clinical performance of these tests was compared at manufacturer-suggested cutoffs. A separate set of 81 patients with a diagnosis of RA by 2010 criteria and whose samples were obtained from within 1-year of RA diagnosis was similarly assessed to evaluate assay performance in an independent clinical RA cohort. Results: Overall diagnostic accuracy was similar; CCP3 had an area under the curve (AUC) of 0.88, CCP3.1 had an AUC of 0.89. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for CCP3 were 79 %, 91 %, 86 %, and 86 %, respectively. For CCP3.1, sensitivity was 78 %, specificity 93 %, PPV 89 %, NPV 86 %. Both assays demonstrated excellent agreement; positive percent agreement of 94 % and negative percent agreement of 99 %. Conclusion: Our findings indicate comparable diagnostic accuracy between CCP3 and CCP3.1 assays in these clinical cohorts.

Multi-Autoantibody Testing Identifies Expansion of Reactivity to Targeted Antigens Before a Diagnosis of Rheumatoid Arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) has a "pre-RA" period in which multiple autoantibodies, including antibodies to citrullinated (cit) proteins (ACPA), rheumatoid factor (RF), anti-peptidyl arginine deiminase (anti-PAD), among others, have been described; however, few studies have tested all autoantibodies in a single pre-RA cohort. This study aims to evaluate the prevalence of multiple autoantibodies in pre-RA and potentially identify an autoantibody profile in pre-RA that indicates imminent onset of clinical RA. METHODS: We evaluated 148 individuals with two pre- and one post-RA diagnosis samples available from the Department of Defense Serum Repository and matched controls. Samples were tested for immuglobulin (Ig) G anti-cyclic cit peptide-3 (anti-CCP3), five ACPA fine specificities, five anti-PAD isoforms, as well as RF IgA and RF IgM using commercial platforms; cutoffs were determined using levels present in <1% of controls. RESULTS: Positivity of anti-CCP3, RF IgA and RF IgM, anti-PAD1, anti-cit-vimentin 2, anti-cit-fibrinogen, and anti-cit-histone 1 increased over time in pre-RA, although anti-PAD and ACPA fine specificities were predominately present within anti-CCP3-positive individuals. Within anti-CCP3-positive samples from the pre-RA period, positivity for RFs as well as anti-PAD and ACPA fine specificities classified samples as being closer to the time of RA diagnosis. CONCLUSION: Multiple autoantibodies are present in pre-RA and increase in positivity as the time of RA diagnosis approaches. These results confirm previous findings predicting imminent RA and provide a pathway using commercial-grade assays to assess the risk for and timing of development of clinical RA.

Understanding the impact of the COVID-19 pandemic and its control measures on women and children: A Zimbabwe case study.

COVID-19 presented countries with unprecedented health policy challenges. For low-income countries in particular, policymakers had to contend with both the direct threats posed by COVID-19 as well as the social, educational, and economic harms associated with lockdown and other infection prevention and control measures. We present a holistic and contextualised case study of the direct and indirect impacts of COVID-19 on women and children, with some assessment of their uneven distribution across socio-economic, age and gender groups. We used different types of primary and secondary data from multiple sources to produce a holistic descriptive analysis. Primary data included: qualitative data obtained from 28 in-depth interviews of key informants, six focus group discussions; and 40 household interviews. We also extracted data from government reports and announcements, the District Health Information Software version 2 (DHIS2), newspaper articles and social media, as well as from published research articles. Our findings show that the direct and indirect adverse impacts of COVID-19 were compounded by many years of severe political economic challenges, and consequent deterioration of the healthcare system. The indirect effects of the pandemic had the most severe impacts on the poorest segment of society and widened age and gender inequalities. The pandemic and its accompanying infection prevention and control measures negatively affected health service delivery and uptake. The management of COVID-19 presented enormous challenges to policymakers and public health specialists. These included managing the greatest tension between direct and indirect harms; short-term and long-term effects; and the unequal distribution of harms across different segments of society.

From autoantibody test results to decision making: Incorporating likelihood ratios within medical practice.

Autoantibodies are important laboratory markers to support diagnosis of autoimmune diseases. Interpretation of autoantibodies is classically done in a dichotomous way (positive versus negative). Yet, interpretation of autoantibody test results can be improved by reporting likelihood ratios. Likelihood ratios convey information on how much more/less likely a test result is in individuals with the disease compared to individuals without the disease. It incorporates information on the antibody level (the higher the antibody level, the higher the association with the disease), which is helpful for (differential) diagnosis. Likelihood ratios are unit-independent and allow users to harmonize test result interpretation. When the likelihood ratio is combined with information on the pre-test probability, post-test probability can be appraised. In this review, the applicability of likelihood ratio in autoimmune diagnostics will be reviewed from the perspective of the clinician, the laboratory professional and the in vitro diagnostic industry.

SARS-CoV-2 Vaccine-Elicited Immunity after B Cell Depletion in Multiple Sclerosis.

The impact of B cell deficiency on the humoral and cellular responses to SARS-CoV2 mRNA vaccination remains a challenging and significant clinical management question. We evaluated vaccine-elicited serological and cellular responses in 1) healthy individuals who were pre-exposed to SARS-CoV-2 (n = 21), 2) healthy individuals who received a homologous booster (mRNA, n = 19; or Novavax, n = 19), and 3) persons with multiple sclerosis on B cell depletion therapy (MS-αCD20) receiving mRNA homologous boosting (n = 36). Pre-exposure increased humoral and CD4 T cellular responses in immunocompetent individuals. Novavax homologous boosting induced a significantly more robust serological response than mRNA boosting. MS-α CD20 had an intact IgA mucosal response and an enhanced CD8 T cell response to mRNA boosting compared with immunocompetent individuals. This enhanced cellular response was characterized by the expansion of only effector, not memory, T cells. The enhancement of CD8 T cells in the setting of B cell depletion suggests a regulatory mechanism between B and CD8 T cell vaccine responses.

Rheumatoid arthritis: prediction of future clinically-apparent disease, and prevention.

PURPOSE OF REVIEW: This review discusses updates in the prediction and prevention of future rheumatoid arthritis (RA). RECENT FINDINGS: In individuals with musculoskeletal symptoms and elevated antibodies to citrullinated proteins (ACPA) without clinical inflammatory arthritis (IA), a 'simple' score has a positive predictive value (PPV) of ∼28% for clinical IA/RA within 1 year, and a comprehensive score (including ultrasound) has a PPV of ∼71% for clinical RA within 5 years. Controlled clinical trials in individuals at-risk for future RA have been performed using corticosteroids, rituximab, atorvastatin, methotrexate, hydroxychloroquine and abatacept. Abatacept modestly reduced rates of incident clinical RA and imaging inflammation within the trials, rituximab delayed clinical IA, and methotrexate improved function, symptoms and imaging inflammation. Vitamin D with or without omega 3 fatty acids reduced incidence of autoimmune diseases, including RA. While not proven in controlled clinical trials, observational studies suggest exercise, weight loss and smoking cessation may reduce progression to clinical RA. SUMMARY: Prediction and prevention of RA is advancing although there are no currently approved interventions for prevention. Future studies should include deeper evaluation of the pathophysiology of RA development to improve prediction and identify key pathways to target in future clinical trials, as well as develop infrastructure to support prevention-related research.

Expansion of HLA-DR Positive Peripheral Helper T and Naive B Cells in Anticitrullinated Protein Antibody-Positive Individuals At Risk for Rheumatoid Arthritis.

OBJECTIVE: To investigate immune dysregulation in the peripheral blood that contributes to the pre-rheumatoid arthritis (RA) stage of RA development in anticitrullinated protein antibody (ACPA)+ individuals. METHODS: Using 37 markers by mass cytometry, we investigated peripheral blood mononuclear cells (PBMCs) from ACPA+ at-risk individuals, ACPA+ early untreated patients with RA, and ACPA- controls in the Tokyo Women's Medical University cohort (n = 17 in each group). Computational algorithms, FlowSOM and Optimized t-Distributed Stochastic Neighbor Embedding, were employed to explore specific immunologic differences between study groups. These findings were further evaluated, and longitudinal changes were explored, using flow cytometry and PBMCs from the US-based Targeting Immune Responses for Prevention of RA cohort that included 11 ACPA+ individuals who later developed RA (pre-RA), of which 9 had post-RA diagnosis PBMCs (post-RA), and 11 ACPA- controls. RESULTS: HLA-DR+ peripheral helper T (Tph) cells, activated regulatory T cells, PD-1hi CD8+ T cells, and CXCR5-CD11c-CD38+ naive B cells were significantly expanded in PBMCs from at-risk individuals and patients with early RA from the Tokyo Women's Medical University cohort. Expansion of HLA-DR+ Tph cells and CXCR5-CD11c-CD38+ naive B cells was likewise found in both pre-RA and post-RA time points in the Targeting Immune Responses for Prevention of RA cohort. CONCLUSION: The expansion of HLA-DR+ Tph cells and CXCR5-CD11c-CD38+ naive B cells in ACPA+ individuals, including those who developed inflammatory arthritis and classified RA, supports a key role of these cells in transition from pre-RA to classified RA. These findings may identify a new mechanistic target for treatment and prevention in RA.

Rheumatoid Arthritis: The Continuum of Disease and Strategies for Prediction, Early Intervention, and Prevention.

Rheumatoid arthritis (RA) is known to include a pre-RA stage that can be defined as the presence of familial or genetic risk factors, biomarker abnormalities (eg, anticitrullinated protein antibodies [ACPA]), symptoms, and even abnormal imaging findings prior to the development of the onset of clinical RA with inflammatory arthritis that is apparent on physical examination. Indeed, there are multiple completed or ongoing retrospective case-control as well as prospective observational studies to identify the key biologic drivers of disease. Further, building on the predictive ability of combinations of biomarkers, symptoms, and imaging for future RA, there are multiple clinical trials completed, underway, or in development to identify approaches that may prevent, delay, or ameliorate future clinical RA in at-risk individuals. Importantly, however, although an effective preventive intervention has not yet been identified, at-risk individuals are being increasingly identified in clinical care; this presents a challenge of how to manage these individuals in clinical practice. This review will discuss the current understanding of the biology and natural history of RA development, nomenclature, and current models for prediction of future RA, as well as evaluate the current and ongoing clinical prevention trials with the overall goal to provide insights into the challenges and opportunities in the field of RA prevention. Moreover, this review will provide up-to-date options for clinical management of individuals at risk for RA.

Short peripheral blood leukocyte telomere length in rheumatoid arthritis-interstitial lung disease.

Shortened telomere lengths (TLs) can be caused by single nucleotide polymorphisms and loss-of-function mutations in telomere-related genes (TRG), as well as ageing and lifestyle factors such as smoking. Our objective was to determine if shortened TL is associated with interstitial lung disease (ILD) in individuals with rheumatoid arthritis (RA). This is the largest study to demonstrate and replicate that shortened peripheral blood leukocytes-TL is associated with ILD in patients with RA compared with RA without ILD in a multinational cohort, and short PBL-TL was associated with baseline disease severity in RA-ILD as measured by forced vital capacity percent predicted.

A potential role for chlamydial infection in rheumatoid arthritis development.

OBJECTIVES: To assess the relationship between self-reported and serologic evidence of prior chlamydial infection, rheumatoid arthritis (RA)-related autoantibodies and risk of RA-development. METHODS: This is a nested study within a prospective Swiss-based cohort including all first-degree relatives of RA patients (RA-FDR) who answered a question on past chlamydial infections. Primary outcome was systemic autoimmunity associated with RA (RA-autoimmunity) defined as positivity for anti-citrullinated peptide antibodies (ACPA) and/or rheumatoid factor (RF). Secondary outcomes were high levels of RA-autoimmunity, RA-associated symptoms and RA-autoimmunity, and subsequent seropositive RA diagnosis. We conducted a nested case-control analysis by measuring the serological status against Chlamydia trachomatis' major outer membrane protein. We replicated our analysis in an independent United States-based RA-FDR cohort. RESULTS: Among 1231 RA-FDRs, 168 (13.6%) developed RA-autoimmunity. Prevalence of self-reported chlamydial infection was significantly higher in individuals with RA-autoimmunity compared with controls (17.9% vs 9.8%, OR = 2.00, 95%CI: 1.27-3.09, p < 0.01). This association remained significant after adjustments (OR = 1.91, 95%CI: 1.20-2.95). Stronger effect sizes were observed in later stages of RA development. There was a similar trend between a positive C. trachomatis serology and high levels of RA-autoimmunity (OR = 3.05, 95% CI: 1.10-8.46, p= 0.032). In the replication cohort, there were significant associations between chlamydial infection and RF positivity and incident RA, but not anti-CCP positivity. CONCLUSIONS: Self-reported chlamydial infections are associated with elevated RA-autoimmunity in at risk individuals. The differing association of chlamydial infections and ACPA/RF between cohorts will need to be explored in future studies but is consistent with a role of mucosal origin of RA-related autoimmunity.

Antinuclear Antibodies Are Associated with an Increased Risk of Diffuse Large B-Cell Lymphoma.

Immune dysregulation is thought to increase the risk of non-Hodgkin lymphoma (NHL), but the evidence varies by subtype. We evaluated whether antinuclear antibodies (ANA), double-stranded DNA antibodies (anti-dsDNA), and extractable nuclear antigen antibodies (anti-ENA) were associated with the risk of common NHL subtypes in a nested case-control study. The autoantibodies were tested in serum collected years prior to NHL diagnosis in 832 cases and 809 controls from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Logistic regression was used to determine odds ratios (ORs) and 95% confidence intervals (95% CI) for the association with NHL risk. No association was observed between ANA positivity and NHL risk overall (OR: 1.18, 95% CI: 0.88-1.58); however, ANA positivity was associated with an increased risk of diffuse large B-cell lymphoma (DLBCL) (OR: 1.83, 95% CI: 1.15-2.91), with 19.7% of cases and 12.2% of controls testing positive. The presence of either anti-ENA or anti-dsDNA was associated with an increased risk of NHL (OR: 2.93, 95% CI: 1.18-7.28), particularly DLBCL (OR: 3.51, 95% CI: 1.02-12.0) and marginal zone lymphoma (OR: 8.86, 95% CI: 1.26-62.0). Our study demonstrates that autoantibodies are associated with an elevated risk of DLBCL, providing support for autoimmunity as a risk factor.

Multifaceted immune dysregulation characterizes individuals at-risk for rheumatoid arthritis.

Molecular markers of autoimmunity, such as antibodies to citrullinated protein antigens (ACPA), are detectable prior to inflammatory arthritis (IA) in rheumatoid arthritis (RA) and may define a state that is 'at-risk' for future RA. Here we present a cross-sectional comparative analysis among three groups that include ACPA positive individuals without IA (At-Risk), ACPA negative individuals and individuals with early, ACPA positive clinical RA (Early RA). Differential methylation analysis among the groups identifies non-specific dysregulation in peripheral B, memory and naïve T cells in At-Risk participants, with more specific immunological pathway abnormalities in Early RA. Tetramer studies show increased abundance of T cells recognizing citrullinated (cit) epitopes in At-Risk participants, including expansion of T cells reactive to citrullinated cartilage intermediate layer protein I (cit-CILP); these T cells have Th1, Th17, and T stem cell memory-like phenotypes. Antibody-antigen array analyses show that antibodies targeting cit-clusterin, cit-fibrinogen and cit-histone H4 are elevated in At-Risk and Early RA participants, with the highest levels of antibodies detected in those with Early RA. These findings indicate that an ACPA positive at-risk state is associated with multifaceted immune dysregulation that may represent a potential opportunity for targeted intervention.

Tumor-Associated and Systemic Autoimmunity in Pre-Clinical Breast Cancer among Post-Menopausal Women.

Autoantibodies to tumor-associated antigens (anti-TAA) are potential biomarkers for breast cancer, but their relationship systemic autoimmunity as ascertained though antinuclear antibodies (ANA) is unknown and warrants consideration given the common occurrence of autoimmunity and autoimmune diseases among women. The relationship between anti-TAAs and ANA among women who were later diagnosed with breast cancer and others who remained cancer free in the Women's Health Initiative cohort. The study sample included 145 post-menopausal women with baseline ANA data. A total of 37 ANA-positive women who developed breast cancer (i.e., cases; mean time to diagnosis 6.8 years [SE 3.9]) were matched to a random sample of 36 ANA-negative cases by age and time to diagnosis. An age-matched control sample was selected including 35 ANA-positive and 37 ANA-negative women who did not develop breast cancer (i.e., controls; follow-up time ~13 years [SE 3]). Baseline sera were assessed for Immunoglobulin G (IgG) antibodies, measured by custom microarray for 171 breast and other cancer-associated TAA. We used linear regression to estimate cross-sectional associations of ANA with log-transformed anti-TAA among cases and controls. Most anti-TAA did not vary by ANA status. Two anti-TAA were elevated in ANA-positive compared to ANA-negative cases: anti-PGM3 (p = 0.004) and anti-TTN (p = 0.005, especially in cases up to 7 years before diagnosis, p = 0.002). Anti-TAA antibodies were not generally related to ANA, a common marker of systemic autoimmunity. Associations of ANA with particular antigens inducing autoimmunity prior to breast cancer warrant further investigation.

Deconstruction of rheumatoid arthritis synovium defines inflammatory subtypes.

Rheumatoid arthritis is a prototypical autoimmune disease that causes joint inflammation and destruction1. There is currently no cure for rheumatoid arthritis, and the effectiveness of treatments varies across patients, suggesting an undefined pathogenic diversity1,2. Here, to deconstruct the cell states and pathways that characterize this pathogenic heterogeneity, we profiled the full spectrum of cells in inflamed synovium from patients with rheumatoid arthritis. We used multi-modal single-cell RNA-sequencing and surface protein data coupled with histology of synovial tissue from 79 donors to build single-cell atlas of rheumatoid arthritis synovial tissue that includes more than 314,000 cells. We stratified tissues into six groups, referred to as cell-type abundance phenotypes (CTAPs), each characterized by selectively enriched cell states. These CTAPs demonstrate the diversity of synovial inflammation in rheumatoid arthritis, ranging from samples enriched for T and B cells to those largely lacking lymphocytes. Disease-relevant cell states, cytokines, risk genes, histology and serology metrics are associated with particular CTAPs. CTAPs are dynamic and can predict treatment response, highlighting the clinical utility of classifying rheumatoid arthritis synovial phenotypes. This comprehensive atlas and molecular, tissue-based stratification of rheumatoid arthritis synovial tissue reveal new insights into rheumatoid arthritis pathology and heterogeneity that could inform novel targeted treatments.

Deep immunophenotyping reveals circulating activated lymphocytes in individuals at risk for rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease with currently no universally highly effective prevention strategies. Identifying pathogenic immune phenotypes in 'At-Risk' populations prior to clinical disease onset is crucial to establishing effective prevention strategies. Here, we applied mass cytometry to deeply characterize the immunophenotypes in blood from At-Risk individuals identified through the presence of serum antibodies to citrullinated protein antigens (ACPA) and/or first-degree relative (FDR) status (n=52), as compared to established RA (n=67), and healthy controls (n=48). We identified significant cell expansions in At-Risk individuals compared with controls, including CCR2+CD4+ T cells, T peripheral helper (Tph) cells, type 1 T helper cells, and CXCR5+CD8+ T cells. We also found that CD15+ classical monocytes were specifically expanded in ACPA-negative FDRs, and an activated PAX5 low naïve B cell population was expanded in ACPA-positive FDRs. Further, we developed an "RA immunophenotype score" classification method based on the degree of enrichment of cell states relevant to established RA patients. This score significantly distinguished At-Risk individuals from controls. In all, we systematically identified activated lymphocyte phenotypes in At-Risk individuals, along with immunophenotypic differences among both ACPA+ and ACPA-FDR At-Risk subpopulations. Our classification model provides a promising approach for understanding RA pathogenesis with the goal to further improve prevention strategies and identify novel therapeutic targets.