Natural killer cell frequency and function in pigs selectively bred for high or low antibody and cell-mediated immune response: Response to vaccination with modified live transmissible gastroenteritis virus

Porcine NK cells are small to medium lymphocytes which are lytic for tumours and virally infected cells when co-cultured for long periods (approximate to 16 h). The frequency and function of NK cells were examined in generation 8 of pigs genetically selected for high (H), low (L), and control (C) antibody (Ab) and cell-mediated immune response (CMIR). The NK phenotype was identified using a pan-species NK-specific murine monoclonal antibody (5C6) and both binding and lysis of the NK target, K562. Vaccination with modified live transmissible gastroenteritis virus (TGEV) had no effect on blood leucocyte NK cell frequency. In interactions with K562, targets, NK cells of PI and C pigs responded similarly in frequency of conjugate formation and lytic activity, while L pigs had very little or no response. Therefore, in pigs selected for high Ab and CMIR, there was no correlated enhancement of NK-cell-related traits following vaccination with TGEV, while selection for low immune response was associated with reduced NK response in pigs. This may suggest that low immune response can reflect reduced contribution of NK cells in pigs.