Precise normalization with reference genes is necessary, in order to obtain reliable relative expression data in response to gastrointestinal nematode infection. By using sheep from temperate regions as models, three reference genes, viz., ribosomal protein LO (RPLO), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and succinate dehydrogenase complex subunit A (SDHA), were investigated in the abomasum, abomasal lymph nodes and small intestine of Brazilian Somalis sheep, either resistant or susceptible to gastrointestinal nematodes infections. Real time PCR was carried out by using SYBR Green I dye, and gene stability was tested by geNorm. RPLO was an ideal reference gene, since its expression was constant across treatments, presented lower variation, and was ranked as the most stable in abomasum and lymph node tissues. On the other hand, SDHA was the most stable in the small intestine followed by RPLO and GAPDH. These findings demonstrate the importance of correctly choosing reference genes prior to relative quantification. In addition, we determined that reference genes used in sheep from temperate regions, when properly tested, can be applied in animals from tropical regions such as the Brazilian Somalis sheep.

T cells produce cytokines that affect host response to infection. This paper reports real-time RT-PCR conditions and validation steps for accurate quantification of Bos indicus cytokines, interleukin (IL)-2, IL-4, IL-8, IL12p-35, IL-13, tumoral necrosis factor (TNF)-alpha, interferon (IFN)-gamma, monocyte chemoattractant proteins (MCP)-1 and MCP-2, and the glycoprotein mucin (MUC)-1 in two groups of Nelore cattle, one resistant and the other susceptible to gastrointestinal nematode infections. RPL-19 was shown to be an ideal internal control gene, since its expression was constant across treatments and presented lower variation when compared to the GAPDH gene. The optimized conditions established in the present study can be used to determine the immune response of cattle under different experimental conditions, such as viral, bacterial and parasite infections.