Distribution of vasoactive intestinal peptide-immunoreactive nerve fibres in submandibular glands. Light microscopic view of vasoactive intestinal peptide (VIP)-immunoreactive (IR) fibres in submandibular gland tissue from (a), (c) a BALB/c mouse and (b) a nonobese diabetic (NOD) mice from Taconic Bomholtgård (Group 1). (a) Thin varicose fibres making a network in a blood vessel wall (arrowheads) in the central part of the gland. (b) VIP-IR fibres (arrowheads) in close proximity to acinar epithelial cells outside a focus of mononuclear cells. Note that the area of mononuclear cells lacks immunoreactivity to VIP. (c) A salivary duct supplied with thin VIP-IR fibres (arrows). (d) Control section from a NOD mouse after preabsorption of antibody with antigen. Scale bars = 50 μm. a, acinar cells; f, focus.