Salivary IgA as a useful non-invasive marker for restraint stress in pigs.

In this study, we investigated the expression of immunoglobulin A (IgA) in porcine salivary gland and its relationship with restraint stress in pigs. IgA was expressed in plasma cells in pig salivary gland, as confirmed by immunohistochemical staining. IgA was also detected in pig saliva itself by ELISA, and salivary IgA levels were increased by a restraint stress. Moreover, there was a circadian rhythm of IgA over the course of a day. These results are the first evidence of IgA expression related to stress in the pig saliva and may make IgA useful as a non-invasive biological marker to evaluate acute stress condition in the pigs.