Insulin-like growth factor-1 attenuates glucocorticoid suppression of pig lymphocyte function

This study evaluated the effects of dexamethasone and insulin-like growth factor-1 on mitogen-induced lymphocyte immune-associated activities including metabolic reduction of the tetrazolium salt and immunoglobulin (Ig) production. Peripheral blood lymphocytes were isolated from blood samples obtained from three 6-week-old male pigs and plated in triplicate for treatment and dose (n=9 wells/treatment/dose). Cells were stimulated with specific doses and combinations of concanavalin A (ConA), pokeweed mitogen (PWM), DEX and/or IGF-1. Both Con A and PWM induced dose-dependent increases (P<0.05) in lymphocyte metabolism and IgM production. Lymphocyte metabolism and IgM production induced by submaximal concentrations of ConA and PWM were dose-dependently suppressed (P<0.05) by DEX. Treatment with IGF-1 attenuated (P<0.5) the suppressive effects of DEX on ConA- but not PWM-induced lymphocyte metabolism. The addition of IGF-1 reduced (P<0.05) DEX suppression of ConA- and PWM-induced IgM production. These results demonstrate that IGF-1 can differentially reduce the suppressive effects of DEX on lymphocytes dependent on mitogen type.