Fc receptor–like (FCRL) 5 is a novel IgG binding protein expressed on B cells, with the capacity to regulate Ag receptor signaling. We assessed FCRL5 expression on circulating B cells from healthy donors and found that FCRL5+ cells are most enriched among atypical CD21−/lo/CD27− tissue-like memory (TLM) B cells, which are abnormally expanded in several autoimmune and infectious diseases. Using multicolor flow cytometry, FCRL5+ TLM cells were found to express more CD11c and several inhibitory receptors than did the FCRL5− TLM subset. The homing receptor profiles of the two TLM subsets shared features consistent with migration away from lymphoid tissues, but they also displayed distinct differences. Analysis of IgH V regions in single cells indicated that although both subsets are diverse, the FCRL5+ subset accumulated significantly more somatic mutations. Furthermore, the FCRL5+ subset had more switched isotype expression and more extensive proliferative history. Microarray analysis and quantitative RT-PCR demonstrated that the two TLM subsets possess distinct gene expression profiles, characterized by markedly different CD11c, SOX5, T-bet, and RTN4R expression, as well as differences in expression of inhibitory receptors. Functional analysis revealed that the FCRL5+ TLM subset responds poorly to multiple stimuli compared with the FCRL5− subset, as reflected by reduced calcium mobilization and blunted cell proliferation. We propose that the FCRL5+ TLM subset, but not the FCRL5− TLM subset, underwent Ag-driven development and is severely dysfunctional. The present study elucidates the heterogeneity of TLM B cells and provides the basis to dissect their roles in the pathogenesis of inflammatory and infectious diseases.
This work was supported by the Intramural Research Program of the Center for Drug Evaluation and Research/U.S. Food and Drug Administration. H.L. was supported by the Research Fellowship Program from the Center for Drug Evaluation and Research administered by the Oak Ridge Associated Universities.
The raw data and normalized results presented in this article have been submitted to the Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/) under accession number GSE66470.
The online version of this article contains supplemental material.
Abbreviations used in this article:
- 7-aminoactinomycin D
- CVID Ia
- type Ia common variable immunodeficiency
- Fc receptor–like
- hepatitis C virus–related mixed cyoglobulinemia vasculitis
- somatic hypermutation
- tissue-like memory
- Ig H chain V region.
- Received May 4, 2015.
- Accepted February 29, 2016.
- Copyright © 2016 by The American Association of Immunologists, Inc.