Abstract：Toll like receptors (TLRs) recognize pathogen ligands and mediates signaling to initiate innate and adaptive immune responses. In this experiment, Chinese holstei and XinJiang brown cattle were used as experimental example. Their genetic polymorphisms of TLR4 gene exon Ⅲ were detected by sequencing first and by PCR-RFLP in the second. Results showed that three poiymorphism loci, TLR4 E3+1656, TLR4 E3+2021 and TLR4 E3+2414,were discovered. Statistical results of χ2 test indicated that two polymorphism sites (TLR4 E3+1656 and TLR4 E3+2021) in the three populations fitted with Hardy-Weinberg equilibrium(P>0.05). The associations were observed between genotypes and SCS by the least square analysis. The results showed that SCS was not significantly affected by different genotypes in TLR4 E3+1656 (P>0.05); the significant different effect between genotype AA and AB was found (P<0.05), the difference was significant between genotype AA and BB was found (P<0.01) and no significant difference were detected between genotype AB and BB(P>0.05) in TLR4 E3+2021 site. In conclusion, the AA genotype in TLR4 E3+2021 site may be the best genotype to resist mastitis, the allele A may play an important role in mastitis resistance in bovine. To research the effect of different genotypes of TLR4 E3+2021 site on SCS, part of the mRNA of the gene expression where in TLRs signaling pathway downstream of Xinjiang brown cattle were detected by Real-Time PCR. The level of Nuclear Factor-kappa b1(NF-κB1), Nuclear Factor-kappa b2(NF-κB2) and Interleukin-1β( IL-1β) transcripts was significantly correlated with genotype of AA and BB in TLR4 E3+2021 (P<0.05), but the level of TLR4, IL-10 and IL-8 transcripts was no significantly correlated with genotype of AA and BB in TLR4 E3+2021(P>0.05).
