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 (Mφ) and dendritic cells (DC) in response to LPS and CD40 ligand (CD40L) stimulations. Splenic Mφ 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 Mφ; 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 Mφ produced IL-12 on LPS stimulation. There was a remarkable difference in the expression of LPS receptor CD14 between Mφ and DC. Mφ 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.