PAS staining. (A) PAS-positive, diastase-resistant “T. whippelii” bacteria in IL-4-deactivated cultures of human peripheral blood mononuclear cells. (Copyright Gabriele Schoedon, Department of Internal Medicine, University Hospital of Zurich.) (B) Macrophages with PAS-positive inclusions in cerebrospinal fluid of a patient with proven neurologic Whipple's disease. (Copyright Gabriele Schoedon.) (C) Right basal ganglion biopsy specimens filled with numerous PAS-positive inclusions from a patient with clinically proven neurologic Whipple's disease. (Copyright Sebastian Brandner, Institute of Neuropathology, University Hospital of Zurich.)