Clonal expansion of CD4+ cytotoxic T lymphocytes in patients with IgG4-related disease

Background IgG 4 -related disease (IgG 4 -RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4 + T cells constitute the major inflammatory cell population in IgG 4 -RD lesions. Objective We used an unbiased approach to characterize CD4 + T-cell subsets in patients with IgG 4 -RD based on their clonal expansion and ability to infiltrate affected tissue sites. Methods We used flow cytometry to identify CD4 + effector/memory T cells in a cohort of 101 patients with IgG 4 -RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor β chain gene was performed on CD4 + SLAMF7 + cytotoxic T lymphocytes (CTLs) and CD4 + GATA3 + T H 2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging. Results CD4 + effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG 4 -RD. Next-generation sequencing revealed prominent clonal expansions of these CD4 + CTLs but not CD4 + GATA3 + memory T H 2 cells in patients with IgG 4 -RD. The dominant T cells infiltrating a range of inflamed IgG 4 -RD tissue sites were clonally expanded CD4 + CTLs that expressed SLAMF7, granzyme A, IL-1β, and TGF-β1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4 + CTLs. Conclusions IgG 4 -RD is prominently linked to clonally expanded IL-1β– and TGF-β1–secreting CD4 + CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4 + T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.