ICOS and immunoglobulin G4-related sclerosing disease: Furthermore, the expressions of all the markers that we studied using immunofluorescence in IL-4–expressing TFH cells from IgG4-RD tissues (BCL6, ICOS, IL-4, CXCR5, BATF, GATA3, and PD1) were consistent with the RNA sequence observations on the tonsillar IL-4–secreting TFH cells.