Sympathetic fibers and no vagal innervation of the spleen.

A. Tyrosine hydroxylase (TH) staining was used to reveal the sympathetic innervation of the spleen. The central arteriole showed high TH positive fibers (blue) that are in close proximity of the T cells (green). B. Texas red amine signal (red) was found occasionally in the B cells area (green). This dextran amine signal was found in mice that exhibit also dextran amine in deep cervical lymph node, indicating that the spleen signal is the result of tracer leakage into the cerebrospinal fluid. The scale bar represents 20 µm.