Effect of Agrimonia procera extract (APE) on TNF α production by porcine PBMC. The TNFα concentration was analyzed in culture supernatant of non-stimulated and LPS (1 μg/ml)-stimulated PBMC (2 × 106 per ml RPMI 1640 medium) treated with 0 or 0.1% APE for 1 and 6 h, respectively. PBMC were isolated from 4 healthy piglets. TNFα was determined using an ELISA. Data represent mean ± SD (n = 4). a,b Bars with different superscript letters within an incubation period differ significantly (P < 0.05, Fisher's test). + tended to be different (P = 0.067, Student's t test).