Ultrastructure of the red pulp in spleen innervation in horse and pig.

This research examines the nerve structure of the red pulp of a pig and horse’s spleen using electron microscopy and immunohistochemistry specific to S-100 protein, revealing unique structures involving smooth-muscle cells, nerve fibres, and reticular cells.

Study Method

• The researchers used electron microscopy and immunohistochemistry specific for S-100 protein to investigate the nerve structures of the red pulp in the spleens of horses and pigs.

Findings in Pig Spleen

• In the pigs’ spleens, there was a large population of smooth-muscle cells extending from the smooth-muscle trabeculae present in the red pulp.
• The reticular cells’ cytoplasmic processes wrapped around the smooth-muscle cells. Also, the nerve fibres were distributed between the smooth-muscle and reticular cells.
• The nerve terminals were found densely clustered towards the smooth-muscle cells.
• There was no discovery of nerve fibers and terminals within the sheathed artery.
• On studying the neurilemma, the researchers showed a reaction positive for the S-100 protein.

Findings in Horse Spleen

• The horses’ red pulp did not show any presence of smooth-muscle cells.
• The nerve fibres terminated around the reticular cells’ cytoplasmic processes.
• Unlike in the pig spleen, nerve fibres and terminals were found in the sheathed artery. These terminals contained both large and small dense-cored vesicles.
• Immunohistochemically, the neurilemma showed a reaction negative for S-100 protein.
• These findings support previous research that described the presence of axon-bearing reticular cells in the horse spleen.

Significance of the Findings

• This research provides a more in-depth understanding of the nerve structures in the red pulp of spleens, more so in the horse and pig species.
• The described variances in muscle cells, nerve structures, and neurilemma reaction to S-100 protein between horses and pigs may lead to better understanding interspecies organ differences.
• Further research can leverage these findings for better understanding of organ function and possible innovations in veterinary medicine.