Abstract: In order to investigate the effects of transmissible gastroenteritis virus (TGEV) infection on the immune organs of piglets, ten healthy 5-day-old piglets were randomly divided into control group and TGEV-infected group (n=5). After 5 days of TGEV infection, the piglets were euthanized and the thymus, spleen, tonsil, inguinal lymph nodes, mesenteric lymph nodes, inferior iliac lymph nodes, superficial cervical lymph nodes and mandibular lymph nodes were collected. The pathological changes of various tissues and organs were observed by hematoxylin-eosin (HE) staining. The distribution of TGEV in various immune organs was also detected by immunohistochemistry (IHC). HE results showed TGEV infection enlarged the thymic lobules, and reduced immune cells in piglets. The red pulp was increased and filled with large numbers of blood cells. The margin between splenic cord and splenic sinus was unclear. Tonsil lymph follicles were decreased. Blood cell infiltrated in the superficial cortical area under the capsule of lymph nodes. IHC results showed that TGEV distributed in a variety of immune organs. The virus load in spleen was the highest, followed by superficial cervical lymph nodes and inguinal lymph nodes, and was least in the thymus. The above results indicate that TGEV infection affect the immune system of piglets, and cause damage to the immune system. This study provides a theoretical basis for the immune pathogenesis of TGEV.

Key words: transmissible gastroenteritis virus, piglets, immune organs, pathological injury, distribution