Differential effects of LPS and CD40 ligand stimulations on the induction of IL-12 production by dendritic cells and macrophages

In this experiment, we have examined the IL-12 production of murine macrophages (M phi) and dendritic cells (DC) in response to LPS and CD40 ligand (CD40L) stimulations. Splenic M phi and DC were purified by sorting on the basis of Mac-1 and CD11c expression and stimulated with LPS or Chinese hamster ovary cells expressing CD40L. The results showed that the ligation of CD40 induced the enhancement of IL-12 p40 mRNA accumulation and IL-12 production in DC as well as in M phi; however, neither the accumulation of IL-12 p40 mRNA nor the production of bioactive IL-12 was detected in DC stimulated with various concentrations of LPS, although M phi produced IL-12 on LPS stimulation. There was a remarkable difference in the expression of LPS receptor CD14 between M phi and DC. M phi evidently expressed CD14 but the CD14 expression of DC was quite low. Possible mechanisms of the failure in IL-12 production of DC are discussed. (C) 1997 Academic Press.