Objective

CD4+FoxP3+ Treg cells suppress effector T cells and prevent autoimmune disease. Treg cell function is deficient in active rheumatoid arthritis (RA), a loss which may play a role in the pathogenesis of this disease. We previously showed that a single-nucleotide polymorphism in the FCRL3 gene led to higher expression of Fc receptor-like 3 (FcRL3) on Treg cells and that FcRL3+ Treg cells are functionally deficient in comparison to FcRL3- Treg cells. This study was undertaken to investigate the potential role of FcRL3 in RA.

Methods

A cross-sectional study was performed to evaluate the FCRL3 -169 genotype and FcRL3 expression on T cell subsets, including Treg cells, in peripheral blood samples from 51 patients with RA enrolled in the University of California, San Francisco (UCSF) RA Cohort. Clinical data were obtained from the UCSF RA Cohort database.

Results

Patients with the FCRL3 -169C allele (genotype C/C or C/T) expressed higher levels of FcRL3 on Treg cells, and on CD8+ and γ/δ T cells, in comparison to RA patients with the T/T genotype. Higher FcRL3 expression on these T cell subpopulations correlated with RA disease activity in patients harboring the FCRL3 -169C allele. Furthermore, FcRL3 expression on Treg cells was higher in patients with erosive RA, and the FCRL3 -169C allele was overrepresented in patients with erosive RA.

Conclusion

Our findings indicate that FcRL3 expression, which is strongly associated with the presence of the FCRL3 -169C allele, may serve as a biomarker for RA disease activity.

Untreated HIV disease is associated with chronic immune activation and CD4(+) T cell depletion. A variety of mechanisms have been invoked to account for CD4(+) T cell depletion in this setting, but the quantitative contributions of these proposed mechanisms over time remain unclear. We turned to the DO11.10 TCR transgenic mouse model, where OVA is recognized in the context of H-2(d), to explore the impact of chronic antigenic stimulation on CD4(+) T cell dynamics. To model dichotomous states of persistent Ag exposure in the presence or absence of proinflammatory stimulation, we administered OVA peptide to these mice on a continuous basis with or without the prototypic proinflammatory cytokine, IL-1β. In both cases, circulating Ag-specific CD4(+) T cells were depleted. However, in the absence of IL-1β, there was limited proliferation and effector/memory conversion of Ag-specific T cells, depletion of peripheral CD4(+) T cells in hematolymphoid organs, and systemic induction of regulatory Foxp3(+)CD4(+) T cells, as often observed in late-stage HIV disease. By contrast, when OVA peptide was administered in the presence of IL-1β, effector/memory phenotype T cells expanded and the typical symptoms of heightened immune activation were observed. Acknowledging the imperfect and incomplete relationship between Ag-stimulated DO11.10 TCR transgenic mice and HIV-infected humans, our data suggest that CD4(+) T cell depletion in the setting of HIV disease may reflect, at least in part, chronic Ag exposure in the absence of proinflammatory signals and/or appropriate APC functions.