TLR2 and infection: Taken together, our results indicated that S. pullorum affects the innate immune response by decreasing the spleen and bursa of fabricius relative weights, serum immunoglobulins concentrations, and the spleen MDA5 and LGP2 mRNA expression levels, and increasing the mRNA expression levels of the spleen NOD1, TLR2, TLR4, DAI, MAVS, P50, P65, and RelB of chickens, consequently increasing the susceptibility of the host to infection.