CD4 and immunoglobulin G4-related sclerosing disease: We have also shown that patients with IgG4-RD exhibit large clonal expansions of CD4+ CTLs, the dominant T cells in disease tissues, and that these cells are activated at lesional sites, where they secrete IL-1β, TGF-β1, and IFN-γ (Mattoo et al, 2016; Maehara et al, 2017).