Additional file 4. Spleen from donor 003 exhibited a unique, robust pattern of NPY staining. (A) Image showing NPY nerve staining around a splenic artery (sa) and staining within surrounding red pulp (rp). Arrow indicates NPY staining of littoral cells. (B) Image showing NPY staining of littoral cells (arrow) in the subcapsular region. Note that the trabeculae (t) and capsule (c) are largely free from NPY staining while the red pulp shows dense staining. (C) Image showing lack of innervation within the white pulp (wp) and limited innervation around a central arteriole (ca.). (D) Image showing intense and abundant staining of littoral cells (arrows) within the red pulp.