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Mixed-Effects Association of Single Cells Identifies an Expanded Effector CD4+ T Cell Subset in Rheumatoid Arthritis

ABSTRACT: High dimensional single-cell analyses have improved the ability to resolve complex mixtures of cells from human disease samples; however, identifying disease-associated cell types or cell states in patient samples remains challenging due to technical and inter-individual variation. Here we present Mixed-Effects modeling of Associations of Single Cells (MASC), a reverse single cell association strategy for testing whether case-control status influences the membership of single cells in any of multiple cellular subsets while accounting for technical confounders and biological variation. Applying MASC to mass cytometry analyses of CD4+ T cells from the blood of rheumatoid arthritis (RA) patients and controls revealed a significantly expanded population of CD4+ T cells, identified as CD27- HLA-DR+ effector memory cells, in RA patients. The frequency of CD27- HLA-DR+ cells was similarly elevated in blood samples from a second RA patient cohort, and CD27- HLA-DR+ cell frequency decreased in RA patients who responded to immunosuppressive therapy. Mass cytometry and flow cytometry analyses indicated that CD27- HLA-DR+ cells were associated with RA. Compared to peripheral blood, synovial fluid and synovial tissue samples from RA patients contained ~5-fold higher frequencies of CD27- HLA-DR+ cells, which comprised ~10% of synovial CD4+ T cells. CD27- HLA-DR+ cells expressed a distinctive effector memory transcriptomic program with Th1- and cytotoxicity-associated features, and produced abundant IFNg and granzyme A protein upon stimulation. Thus MASC identified the expansion of a unique effector memory CD4+ T cell population in RA. We propose that MASC is a broadly applicable method to identify disease-associated cell populations in high-dimensional single cell data.

ORGANISM(S): Homo sapiens

PROVIDER: GSE118209 | GEO | 2018/09/13

REPOSITORIES: GEO

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Project description:HLA-DR molecules are highly expressed in synovial tissue (ST), the target of the immune response in chronic inflammatory arthritides, including in rheumatoid arthritis (RA) and Lyme arthritis (LA). In the current study, we identified HLA-DR-presented self-peptides (T cell epitopes) in ST, synovial fluid mononuclear cells (SF), and peripheral blood mononuclear cells (PB) from five patients with RA and eight with LA. Altogether, from 22 samples, 1,532 non-redundant HLA-DR-presented peptides were identified that were derived from 778 source proteins. Moreover, as the study progressed, application of newer, high sensitivity LC-MS instruments resulted in the identification of larger numbers of HLA-DR-presented peptides. Surprisingly, the source proteins for HLA-DR-presented peptides were as likely to have intracellular as extracellular locations. Although the number of peptides identified was greater in ST than in SF or PB, 68% of the peptides identified in SF were found in ST, and 55% of the peptides in PB were found in ST. Two RA patients had the same HLA-DR genotype (DRB1*0401 and 0101), and 44% of the peptides identified in these two patients were the same. In contrast, among the patients with RA or LA who had no shared HLA-DR alleles, only 6% of the peptides were the same. In the RA patients, HLA-DR-presented peptides were identified from source proteins that are thought to serve as potential autoantigens: collagen, enolase, fibrinogen, fibronectin, immunoglobulin and vimentin. Interestingly, peptides from these same source proteins were also commonly found in LA patients. However, citrullinated T cell epitopes were not identified in any patient. Thus, LC-MS/MS techniques are now sensitive enough to identify large numbers of T cell epitopes from tissue or fluids in individual patients. Importantly, analysis of SF or PB allowed us to identify a broader range of HLA-DR-presented self-peptides from individual patients and from patients seen earlier in the disease.

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Mixed-Effects Association of Single Cells Identifies an Expanded Effector CD4+ T Cell Subset in Rheumatoid Arthritis

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