Evaluation of Polymorphism of the Immune System Genes TNF and TLR2 in Cattle

In this article the results of genotyping of tumor necrosis factor (TNF) and Toll-like receptor 2 (TLR2) genes among 644 head of cattle of six breeds belonging to four different genetic roots are presented. The Kholmogory and Holstein breeds of black-and-white root, the Ayrshire breed of red root, the Kostroma and Brown Swiss breed of brown root, and the fawn Simmental breed were studied. The PCR-RFLP method was used to identify alleles and genotypes. Significant differences in allele frequency of the TNF and TLR2 genes were observed between breeds of different genetic roots (p < 0.001) and between breeds of dairy and dairy-meat productivity (p < 0.001). In five of the six cattle breeds studied, the predominance of the TLR2^T allele was revealed. The highest frequency of the TLR2^T allele (0.99) was found in the Ayrshire breed. The herd of Ayrshire cows is close to being monomorphic for the TLR2 gene; 98% of the animals have the homozygous TLR2^TT genotype. A more uniform distribution of alleles and genotypes for the TLR2 gene was found in black-and-white animals: in Holstein cattle, the average frequency of the TLR2^T allele was 0.78; in Kholmogory cattle, it was 0.83. The TLR2^TT genotype was detected in the majority of Holstein (61%) and Kholmogory (69%) cows. The frequency of the TLR2^T allele in the Simmental breed was 0.62; in the Kostroma breed, it was 0.67. In Simmental and Kostroma cows, the heterozygous TLR2^TG genotype is more common (54 and 47% respectively). A different picture of the distribution of allele and genotype frequencies was revealed in Brown Swiss animals. The TLR2^T allele frequency averages 0.26. More than half of Brown Swiss cows (55%) are homozygous for TLR2^GG. In all breeds, the TNF^B allele predominated with a frequency of occurrence ranging from 0.61 in Holstein cattle to 0.98 in the Brown Swiss breed. A high frequency of the TNF^B allele was found in the Kostroma (0.94), Ayrshire (0.885), and Simmental (0.80) breeds. In the Kholmogory breed, the average frequency of the TNF^B allele was 0.72. The highest frequency of the TNF^BB genotype was found in Brown Swiss herds (96%). The predominance of the homozygous TNF^BB genotype was revealed in Kholmogory (53%), Simmental (62%), Ayrshire (77%), and Kostroma cattle (87.5%). In Holstein cows, the majority of animals (53%) carry the heterozygous TNF^АВ genotype. In three breeds, Ayrshire, Kostroma, and Brown Swiss, the TNF^AA genotype was not detected.