rTsAP facilitation or anti-rTsAP serum suppression on IEC invasion by intestinal infective larvae (IIL).Trichinella spiralis ML were first activated into the IIL larvae with 5% swine bile for 2 h at 37 °C, the IIL were added onto the IEC monolayer and the penetration was examined under a microscope at 2 h after co-culture. A, B Larvae invaded into the IEC monolayer was active, and the integrity of the IEC monolayer invaded by the IIL larvae was destroyed. C Non-penetrated IIL coiled on the surface of the IEC monolayer. D Non-penetrated IIL coiled on the surface of the C2C12 monolayer. E rTsAP promoted the IIL invasion of IEC, but the promotion was suppressed by enzymatic inhibitor phenanthroline. F Inhibition of anti-rTsAP immune serum on the IIL invasion of IECs. * P < 0.01 compared to the BSA, rTsAP + phenanthroline or pre-immune serum group. Scale-bars: 100 μm.