Tissue specificity and species superiority of cathelicidin gene expression in Chinese indigenous Min pigs

Antimicrobial peptides (AMPs) are components of innate immunity, forming the first-line of defense used by many organisms against the invading pathogens. Min pigs are a Chinese indigenous breed with low mortality and strong disease resistance. In this study, the mRNA expressions of four cathelicidins (PMAP-23, PMAP-37, PR-39, and protegrin-1), the largest family of AMPs in pigs, were determined by real-time PCR in 14-day-old Min pigs and Landrace pigs were chosen as the control. The results showed that expression of four cathelicidin mRNAs in most tissues were higher in Min pigs than those of Landrace pigs, which may partly explain the higher immunity and disease resistance of Min pigs. The cathelicidin molecules were generally expressed at high levels in thymus, spleen, liver, and heart, and at low levels in ileum, jejunum, tongue, and lymph node in both breeds. The peptide pairs with significant correlation in one breed were generally not correlated with these in the other breed, suggesting differential synergistic or antagonistic regulation of cathelicidins in Min pigs and Landrace pigs. The high expression of cathelicidins might be one of the mechanisms by which the Min pigs display strong disease resistance.