Abstract: Interleukin 1 receptor antagonist （IL1RN） is an important host immunoregulatory factor and is a natural IL-1 antagonist. This study aimed to characterize the cellular and tissular expression of IL1RN gene in weaned piglets of two local pig breeds in Shanxi Province. The total RNA of 18 tissues and cells, including heart, liver, spleen, lymphocytes, macrophages, etc.,of Jinfen white piglets and new Shanxi black piglets was extracted by Trizol method. The expression of IL1RN gene in different tissues and cells of the piglets was determined by RT-PCR assay. The expressional difference of IL1RN gene in four immune related tissues and cells （spleen, lymph nodes, macrophages, white blood cells） between the two local pig breeds were statistically compared with SPSS 19.0 software. The results showed that except for adipose tissue, the expression of IL1RN gene was observed in all the other tested tissues and cells in both of the two local pig breeds; extremely significant （P<0.01） expressional difference in IL1RN gene between macrophages and lymph nodes, spleen, white blood cells in Jinfen white piglets was found, and that between lymph nodes and spleen, white blood cells were also observed; the expressional difference in IL1RN gene between spleen, lymph nodes, macrophages and white blood cells in new Shanxi black piglets was extremely significant （P<0.01） when compared pairwisely; there were extremely significant （P<0.01） expressional differences in IL1RN gene in spleen, macrophages and white blood cells between the two local pig breeds, and significant （P<0.05） expressional difference in IL1RN gene in lymph nodes between the two local pig breeds was found. Our results provide a basis for further unraveling the function and underling mechanism of the IL1RN gene in disease resistance in the two local pig breeds.

Key words: IL1RN gene, Jinfen white pig, new Shanxi black pig, piglets, expressional difference, RT-PCR