SIGNAL TRANSDUCTION EVENTS IN CHICKEN INTERLEUKIN-1 PRODUCTION

The HD11 chicken macrophage cell line was studied for growth characteristics using different culture media, serum concentrations, and incubation temperatures. Growth curves at 37 C revealed that the cells grew best in RPMI 1640 medium supplemented with 10% colostrum-free bovine serum (CFBS). Growth was not supported by RPMI 1640 medium supplemented with the serum replacement Nu Serum nor by PC-1 culture medium alone. However, coating culture plates with either chicken serum or Nu Serum enhanced HD11 cell growth in the PC-1 medium. Growth at 40 C was equivalent to that obtained at 37 C when RPMI 1640 medium with 10% CFBS or PC-1 medium in plates coated with chicken serum were used. Several stimuli were tested for their ability to induce interleukin-1 (IL-1) in HD11 macrophages under serum-free conditions. Lipopolysaccharide (2.5-mu-g/mL) or silica (50-mu-g/mL), increased extracellular IL-1 significantly after a 24-h treatment. In contrast, a superinduction protocol using phorbol 12-myristate 13-acetate, cycloheximide, butyrate, and actinomycin D did not increase extracellular IL-1 significantly. All three stimulants significantly elevated intracellular IL-1 after treatment. Protein kinase C inhibitors (H7 and retinal) as well as calmodulin-dependent kinase inhibitors (W7 and TFP) significantly diminished IL-1 production in the intracellular and extracellular compartments. Elevated cyclic adenosine 5'-monophosphate (cAMP) actuated by dibutyryl cAMP also increased IL-1 significantly. The data indicate that both protein kinase C and calmodulin-dependent kinase mechanisms are important in signal transduction leading to IL-1 production.