title: Ontogeny of intrinsic innervation in the human thymus and spleen.
abstract: The ontogeny of the innervation of human lymphoid organs has not been studied in detail. Our aim was to assess the nature and distribution of parenchymal nerves in human fetal thymus and spleen. We used the peroxidase immunohistochemical technique with antibodies specific to neuron-specific enolase (NSE), neurofilaments (NF), PGP9.5, S100 protein, and tyrosine hydroxylase (TH) and evaluated our results with image analysis. In human fetal thymus, NSE-, NF-, S100-, PGP9.5-, and TH-positive nerves were identified associated with large blood vessels from 18 gestational weeks (gw) onwards, increasing in density during development. Their branches penetrated the septal areas at 20 gw, reaching the cortex and the corticomedullary junction between 20 and 23 gw. Few nerve fibers were seen in the medulla in close association with Hassall's corpuscles. In human fetal spleen, NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers were localized in the connective tissue surrounding the splenic artery at 18 gw. Perivascular NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers were seen extending into the white pulp, mainly in association with the central artery and its branches, increasing in density during gestation. Scattered NSE-, NF-, S100-, PGP9.5-, and TH-positive nerve fibers and endings were localized in the red pulp from 18 gw onward. The predominant perivascular distribution of most parenchymal nerves implies that thymic and splenic innervation may play an important functional role during intrauterine life.
authors: Laboratory of Histology and Embryology, Medical School, National and Kapodistrian University of Athens, 75 M. Asias Str, 11527 Athens, Greece. aisantha@hotmail.com
authors: Valsamo K
authors: VK
authors: Anagnostou
authors: Ipatia
authors: I
authors: Doussis-Anagnostopoulou
authors: Dina G
authors: DG
authors: Tiniakos
authors: Despina
authors: D
authors: Karandrea
authors: Emmanouil
authors: E
authors: Agapitos
authors: Petros
authors: P
authors: Karakitsos
authors: Christos
authors: C
authors: Kittas
mesh_terms: D005333:Fetus / Q000294:innervation; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D009412:Nerve Fibers / Q000648:ultrastructure; D013154:Spleen / Q000098:blood supply / Q000196:embryology / Q000294:innervation*; D013950:Thymus Gland / Q000098:blood supply / Q000196:embryology / Q000294:innervation*