Abstract：Screening immune-related genes is important for pig (Sus scrofa) disease resistant breeding. In our previous genome-wide association study (GWAS) of T lymphocyte subpopulation traits in piglets (Sus scrofa)，an immune regulation region of 1.05 Mb was identified, which contained 6 immune-related genes, that is, cluster of differentiation 4 (CD4), lymphocyte activation gene-3 (LAG3), cluster of differentiation (CD27), lymphotoxin beta receptor (LTBR), tumor necrosis factor receptor superfamily member 1a (TNFRSF1A) and cluster of differentiation (CD9). In the present study, to unravel the 6 genes expression differences between breeds with different disease resistance, one typical Chinese indigenous breed (Dapulian) with higher disease resistance in North China and one commercial breed (Landrace) with lower disease resistance were used. Blood samples of clinically healthy Dapulian (n=104) and Landrace (n=171) piglets of 35 d old were collected, and their total RNA was extracted and reverse-transcribed into cDNA. Firstly, the mRNA expressions of these 6 genes and the reference gene beta-2-microglobulin (B2M) were determined by quantitative real-time PCR (qRT-PCR). Then, after normalization with reference gene B2M, Six immune-related genes expression characteristics and breed effects were performed analyses in the 2 breeds. The piglets used in this study were sampled from 13 Dapulian sows and 28 Landrace sows, finally, litter effect on these genes expression was also analyzed. The results of this study showed that the expressions of these 6 immune-related genes in Dapulian and Landrace were lower than the reference gene (B2M), and individual difference in the population was small, with variation coefficients of 5.92~15.96 and 5.99~12.43 in Dapulian and Landrace respectively. Comparison between the 2 breeds, there were significant difference in the expression levels of CD4, CD27, TNFRSF1A and CD9. Specifically, the expressions of CD4, CD27 and TNFRSF1A in Dapulian piglets were significantly lower than those in Landrace at 0.01 or 0.05 level, and expression of CD9 in Dapulian piglets was significantly higher than that in Landrace at 0.01 level. The litter effect of CD4 and CD27 reached significance level (P＜0.01). Our results indicated that CD4, CD27, TNFRSF1A and CD9 were differently expressed between Dapulian and Landrace piglets, which may be considered as candidate genes affecting the high resistance of Dapulian, and used in the study of marked assisted selection.
