Correlated response of peripheral blood cytokines with selection for reduced mycoplasma pneumonia of swine lesions in Landrace pigs

Mycoplasma pneumonia of swine (MPS) is responsible for significant economic losses in the swine industry. We selected Landrace pigs for reduced MPS pulmonary lesions over five generations, and measured concentrations of the following cytokines: interleukin (IL)-10, IL-13, IL-17, tumor necrosis factor (TNF)-α and interferon (IFN)-γ to estimate their correlation with MPS lesions. Sheep red blood cells (SRBC) were injected twice intramuscularly at 70 and 95 kg body weight. Blood serum samples were collected after 1 week of secondary SRBC inoculation and cytokine concentrations were analyzed by ELISA. Genetic parameters and breeding values were estimated. The heritability estimates of IL-10, IL-13, IL-17, TNF-α and IFN-γ were 0.20 ± 0.06, 0.12 ± 0.06, 0.27 ± 0.07, 0.20 ± 0.10 and 0.05 ± 0.03, respectively. Genetic correlations of IL-17 and TNF-α with pulmonary MPS lesions were high (-0.86 ± 0.13 and 0.69 ± 0.29, respectively) and those of IFN-γ and IL-13 with MPS lesions were moderately negative (-0.45). Through selection, the breeding values of IL-17 and IFN-γ increased substantially and those of TNF-α decreased. These results suggest that innate and cellular immunity are more important for the suppression of pulmonary lesions in MPS than humoral-mediated immunity, such as antibody response.