Figure 2.

Pathways of neurommunological integration. Afferent and efferent pathways have a neural and a humoral component. The sympathetic nervous system innervates the primary and secondary lymphoid organs. The vagus nerve, which is part of the parasympathetic autonomic nervous system, has both afferent and efferent neurons, participating in both pathways. Cytokines can cross the blood–brain barrier and the hypothalamus–hypophysis–adrenal axis is responsible for humoral efference. ACTH: Adrenocorticotropic hormone; CRH: Corticotropin-releasing hormone.