[ Objective] The research aimed to explore effects of an immunological stress on immune response in different breeds of piglets （ Lulai pig, Laiwu pig and Yorkshire pig）. [Method] All the 12 weaning pigs （Lulai pig, Laiwu pig and Yorkshire pig） weighing （12.6 ±0.5） kg were used in a 2 x3 factorial design. The main factors consisted of immunological challenge （ LPS or saline） and breeds （ Lulai pig, Laiwu pig and Yorkshire pig）. On Day 1, six piglets of each breed were injected with LPS at the usage of 200 μg/kg BW or an equivalent amount of sterile saline, and in jected classical swine fever vaccine at the same time. Blood sample were collected on Day 2, 7 and 14 post injection to analyze the blood lympho cyte proliferation. The levels of antibodies against classical swine fever were tested on Day 1 prior to injection and on Day 7 and 14 post injection. [ Result] On Day 2 after injection, the lymphocyte transformation rate of piglets injected with LPS were significantly （P〈O. 01 ） increased compared with piglets injected with saline. The lymphocyte transformation rate of Laiwu piglets was significant higher than that of Yorkshire piglets （ P 〈 0.05）. Effects of immunological stress on the level of antibodies against classical swine fever were not significantly different among different breeds of pig lets. [ Conclusion] LPS can effectively stimulate cellular immunity response in different breeds of piglets, and the immune response ability is different among various breeds of piglets.
