Calcium dependency of interleukin-1 secretion by a chicken macrophage cellline

The role of calcium in transducing the signal for interleukin-1 (IL-1) secr etion was examined in the MQ-NCSU chicken macrophage cell line. Cells were maintained in RPMI 1640 medium supplemented with 5% chicken serum and antib iotic-antimycotic solution at 40 C and 5% CO2. The effects of stimulation w ith Lipopolysaccharide (LPS), calcium ionophore A23187, or a combination of both on IL-1 secretion were examined. Calcium ionophore A23187 did not rep lace LPS in MQ-NCSU stimulation but the LPS + A23187 combination stimulated more IL-1 than ionophore alone in these cells. The combination of LPS and ionophore did not increase IL-1 secretion above the levels observed with LP S alone. No synergistic effects between LPS and A23187 were evident. In order to dem onstrate that IL-1 secretion by the MQ-NCSU cells is a calcium-dependent pr ocess, ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA) was used to chelate free calcium in the cultures. Incorporation of 5 mM EGTA in the cultures lowered IL-1 stimulated by LPS + A23187 to contro l levels. Addition of 5 mM CaCl2 to EGTA-suppressed cultures restored IL-1 secretion. These results indicate that the calcium ionophore, A23187, augme nts IL-1 secretion by LPS-stimulated MQ-NCSU macrophages and that IL-1 secr etion by these cells is a calcium-dependent process.