Objective
To estimate the incidence and prevalence of systemic lupus erythematosus (SLE) in a sociodemographically diverse southeastern Michigan source population of 2.4 million people.
Methods
SLE cases fulfilling the American College of Rheumatology classification criteria (primary case definition) or meeting rheumatologist-judged SLE criteria (secondary definition) and residing in Wayne or Washtenaw Counties during 2002–2004 were included. Case finding was performed from 6 source types, including hospitals and private specialists. Age-standardized rates were computed, and capture–recapture was performed to estimate underascertainment of cases.
Results
The overall age-adjusted incidence and prevalence (ACR definition) per 100,000 persons were 5.5 (95% confidence interval [95% CI] 5.0–6.1) and 72.8 (95% CI 70.8–74.8). Among females, the incidence was 9.3 per 100,000 persons and the prevalence was 128.7 per 100,000 persons. Only 7 cases were estimated to have been missed by capture–recapture, adjustment for which did not materially affect the rates. SLE prevalence was 2.3-fold higher in black persons than in white persons, and 10-fold higher in females than in males. Among incident cases, the mean ± SD age at diagnosis was 39.3 ± 16.6 years. Black SLE patients had a higher proportion of renal disease and end-stage renal disease (ESRD) (40.5% and 15.3%, respectively) as compared to white SLE patients (18.8% and 4.5%, respectively). Black patients with renal disease were diagnosed as having SLE at younger age than white patients with renal disease (mean ± SD 34.4 ± 14.9 years versus 41.9 ± 21.3 years; P = 0.05).
Conclusion
SLE prevalence was higher than has been described in most other population-based studies and reached 1 in 537 among black female persons. There were substantial racial disparities in the burden of SLE, with black patients experiencing earlier age at diagnosis, >2-fold increases in SLE incidence and prevalence, and increased proportions of renal disease and progression to ESRD as compared to white patients.
We found no association between PBB serum levels and diabetes incidence. In women, there was a positive linear association of diabetes incidence with PCB serum levels at enrollment. This finding is in agreement with 2 prior studies indicating a higher relative risk of diabetes in PCB-exposed women.
Recognizing that Arab and Chaldean Americans experience different disease burdens from Whites is a first step toward earlier diagnosis and designing targeted interventions. Better methods of assigning ethnicity would improve research in this population.
Background: CD4 T cells help B cells produce antibodies following antigen challenge. This response classically occurs in germinal centers (GC) located in B-cell follicles of secondary lymphoid organs (SLO), a site of immunoglobulin isotype switching and affinity maturation. GC formation requires specialized CD4 T cells, T-follicular helper (Tfh) cells, which localize to follicles and provide B cells with survival and differentiation signals that are essential for B-cell maturation into memory and long-lived plasma cells. Pathogenic autoantibodies in human and murine lupus arise in a like manner. Although Tfh cells are critical for GC development, their genesis in humans, role in promotion of autoimmunity, and potential as therapeutic targets in SLE are incompletely understood. To address these issues, we dissected Tfh cell development and function, defining their transcriptional regulation, migration, and function in vivo in normal and lupus-prone mice and ex vivo in normal humans and patients with SLE. Methods: We used a combination of approaches-flow cytometry, confocal microscopy, microarrays, quantitative chromatin immunoprecipitation and DNA sequencing (ChIP-seq), retroviral overexpression, and T-cell-B-cell helper assays-to characterize Tfh cells in normal mice and in lupus-prone strains, and from the tonsils of normal humans and the blood of patients with SLE. Results: We found that the transcription factor Bcl6 (B-cell CLL/lymphoma 6) is necessary and sufficient for Tfh development and function, via genetic control of Tfh proteins that are essential for their migration to B-cell follicles and GC and subsequent B-cell maturation. We dissected steps in Tfh development within SLO, beginning with their genesis in the T-cell zone followed by emigration to sites of B-cell interaction outside the B-cell follicle, where we have shown that B cells serve to provide signals for continued Tfh expansion and follicular migration. We have now begun to tease apart the factors that mediate T-cell-B-cell collaboration in the follicle; these represent therapeutic targets in SLE. Finally, we have shown that patients with SLE have expansion of Tfh cells in the blood, a finding that highlights their potential role in the pathogenesis of SLE and as likely therapeutic targets. Conclusion: These studies help define the developmental pathways for Tfh cells, and the steps that enable these cells to function in the B-cell follicle to promote immunoglobulin and autoantibody production. They have also helped define markers of Tfh cells in normals and autoimmune individuals, and suggest that they are a promising therapeutic target in patients.
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