DIFFERENTIAL STIMULATION REQUIREMENTS FOR IL-12 PRODUCTION AMONG CLONES OF MACROPHAGE HYBRIDOMAS

We have previously established cloned macrophage hybridomas by somatic cell fusion of the macrophage tumor P388D(1) of DBA/2 (H-2(d)) origin with splenic adherent cells of CKB mice (H-2(k)). Several cloned line s displayed the serologic and functional characteristics of macrophage s, In this study, we evaluated the ability of these hybridomas to prod uce IL-12 after combined stimulation with IFN-gamma and lipopolysaccha ride (LPS), The patterns of IL-12 production by these cloned macrophag es fell into three groups. The first group produced IL-12 on stimulati on with LPS in combination with IFN-gamma pretreatment, the second gro up produced IL-12 on stimulation with LPS regardless of the pretreatme nt with IFN-gamma, and the third group did not produce IL-12 at all on stimulation with IFN-gamma and LPS. None of the macrophage clones tes ted produced IL-12 constitutively. The results correlated well with IL -12 p40 mRNA expression in those macrophages as detected by RT-PCR. Th ese results suggest the differential stimulation requirements for IL-1 2 production among macrophages at a clonal level.