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 selected for increased 16-wk BW and its corresponding randombred control (RBC2). The PBMC were isolated by centrifugation over Histopaque-1077 density gradient and tested for mitogenic responses to concanavalin A (Con A; 25 microg/mL) and phytohemagglutinin (PHA)-M; 100 microg/mL). For the whole blood assay, 6-wk-old poults from both lines were injected with inactivated Pasteurella 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 microg/mL) and PHA-M (25 microg/mL). The cultures were then pulsed with 3H-thymidine, and incorporation was measured using a liquid scintillation counter. There was a line difference in the mitogenic responses to Con A for PBMC and whole blood assays, but no line difference was observed in the response to PHA-M for both assays. For the purified PBMC assay, the F line had a lower response than its randombred control line (P < or = 0.05) to Con A expressed as either cpm or a stimulation index (SI; ratio of cpm for 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 postinjection (P < or = 0.01) and at 14 d postinjection (P < or = 0.05). Genetic selection for increased BW might have affected the lymphoblastogenic potential of Line F that could affect disease resistance.