IL-17RB⁺ T cells and IL-25 are expressed in vasculitic lesions of CSS patients. (A) Immunohistochemical analyses of nerve tissue specimens from patients with CSS, MPA, and noninflammatory neuropathy. IL-25 and IL-17RB were expressed within the perivascular infiltrates in patients with CSS, compared with that in patients with MPA and those with noninflammatory idiopathic neuropathy (original magnification ×540; × 1080 for the inserts in CSS panels). (B) H&E staining. Mononuclear cells and eosinophils (black arrows) were observed within the perivascular inflammatory infiltrate (original magnification ×540; ×1080 for the insert). (C) Immunofluorescence microscopy analysis of frozen nerve tissue specimen from CSS patients revealed expression of the eosinophil granule Major Basic Protein (MBP) and colocalization of IL-17RB with CD3 within the perivascular infiltrates, indicating that infiltrating IL-17RB–expressing cells were T cells (original magnification ×270 for negative control and MBP; ×540 for CD3 and IL-17RB staining). Immunohistochemistry and immunofluorescence images were acquired using a Leica DMI6000B microscope (Leica) and analyzed using the Metaview software.