Effect of selection for increased body weight on mitogenic responses in turkeys

Mitogenic responses were;examined for purified peripheral blood mononuclear cells (PBMC) and whole blood from individuals in a line (F) of turkeys sel ected for increased 16-wk BW and its corresponding randombred control (RBC2 ). The PBMC were isolated by centrifugation over Histopaque-1077 density gr adient and tested for mitogenic responses to concanavalin A (Con A; 25 mu g /mL) and phytohemagglutinin (PHA)-M; 100 mu g/mL). For the whole blood assa y, 6-wk-old poults from both lines were injected with inactivated Pasteurel la multocida. Heparinized blood samples;were collected prior to injection ( 0 d) and at 2,4, 7 and 14 d postinjection. The diluted whole blood was then tested for the mitogenic responses to Con A (25 mu g/mL) and PHA-M 125 mu g/mL). The cultures were then pulsed with H-3-thymidine, and incorporation was measured using a liquid scintillation counter. There was a line difference in the mitogenic responses to Con A for PBMC an d whole blood assays, but no line difference was observed in the response t o PHA-M fur both assays. For the purified PBMC assay, the F line had a lowe r response than its randombred control Line (P less than or equal to 0.05) to Con A expressed as either cpm or a stimulation index (SI; ratio of cpm f or stimulated cells to the cpm for unstimulated cells). For the whole blood assay, the F line had generally lower SI values in the responses to Con A than the RBC2 line, with differences being significant at 0 and 2 d postinj ection (P less than or equal to 0.01) and at 14 d postinjection (P less tha n or equal to 0.05). Genetic selection for increased BW might have affected the lymphoblastogenic potential of Line F that could affect disease resist ance.