Immunogenic properties of Landrace pigs selected for resistance to mycoplasma pneumonia of swine.

Mycoplasma pneumonia of swine (MPS) lung lesions and immunogenic properties were compared between a Landrace line that was genetically selected for reduced incidence of pulmonary MPS lesions, and a non-selected Landrace line. The MPS-selected Landrace line showed significantly lower degrees of pulmonary MPS lesions compared with the non-selected Landrace line. When changes in immunity before and after vaccination were compared, the percentage of B cells in the peripheral blood of the MPS-selected Landrace line was significantly lower than that of the non-selected line. Furthermore, the concentration of growth hormone and the mitogen activity of peripheral blood mononuclear cells in the MPS-selected Landrace line showed significantly (P < 0.05) lower increases after vaccination than the non-selected line. Conversely, the concentration of peripheral blood interferon (IFN)-γ and salivary immunoglobulin A (IgA) after Mycoplasma hyopneumoniae vaccination was significantly higher in the MPS-selected Landrace line than in the non-selected line. Gene expression of toll-like receptor (TLR)2 and TLR4 was significantly higher in the MPS-selected Landrace line in immune tissues, with the exception of the hilar lymph nodes. The present results suggest that peripheral blood IFN-γ, salivary IgA TLR2, and TLR4 are important immunological factors influencing the development of MPS lesions.