Mixed Effects Association of Single Cells Identifies an Expanded Th1-Skewed Cytotoxic Effector CD4+ T Cell Subset in Rheumatoid Arthritis.

Citation:

Fonseka CY, Rao DA, Teslovich NC, Hannes SK, Slowikowski K, Gurish MF, Donlin LT, Weinblatt ME, Massarotti EM, Coblyn JS, Helfgott SM, Todd DJ, Bykerk VP, Karlson EW, Ermann J, Lee YC, Brenner MB, Raychaudhuri S. Mixed Effects Association of Single Cells Identifies an Expanded Th1-Skewed Cytotoxic Effector CD4+ T Cell Subset in Rheumatoid Arthritis. Science Translational Medicine 2018;10(463)

Abstract:

High dimensional single-cell analyses have dramatically 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 novel 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 confounds and biological variation. Applying MASC to mass cytometry analyses of CD4+ T cells from 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 (OR = 1.7; p = 0.0011). 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 respond to immunosuppressive therapy. 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. We find that CD27- HLA-DR+ cells are abundant producers of IFN-γ and also express perforin and granzyme A at elevated levels. Thus MASC identified the expansion of a unique Th1 skewed effector T cell population with cytotoxic capacity in RA. We propose that MASC is a broadly applicable method to identify disease-associated cell populations in high-dimensional single cell data.