Effects of peripheral blood mononuclear cells on Haemonchus contortus larval motility in vitro

Summary The objective of this experiment was to determine effects of peripheral blood mononuclear cells ( PBMC ), derived from parasite‐resistant St. Croix ( STC ) and parasite‐susceptible Suffolk ( SF ) sheep, on motility of Haemonchus contortus L 3 stage larvae in vitro . Peripheral blood mononuclear cells were collected from 10 lambs of each breed, 5 naïve and 5 which had received a priming infection with H. contortus . Larval motility was quantified using a MIF Nikon Sweptfield microscope and NIS Elements AR software, and measurements included path length ( PL ) (μm), velocity ( VEL ) (μm/s) and acceleration ( ACC ) (μm/s 2 ). After 18 h of incubation, PL and VEL were greatest in larvae cultured with SF ‐derived PMBC and were significantly different from all other groups ( P  <   0·01). No difference was observed in PL or VEL between larvae exposed to naïve or primed STC ‐derived PBMC and primed‐ SF PBMC . Differences in ACC were detected between larvae cultured with primed STC ‐derived PBMC (10·91 μm/s 2 ) and naïve SF ‐derived PBMC (45·7 μm/s 2 ) ( P  =   0·035). These data indicate an innate ability of STC ‐derived PBMC to severely inhibit larval motility.