DIFFERENTIATION OF A MURINE PRE-B-CELL LINE BY AN ADJUVANT MURAMYL PEPTIDE VIA NF-KAPPA-B ACTIVATION

Muramyl dipeptide (MDP) induces NF-kappa B activation in the murine pr e-B cell line 70Z/3, increases the expression of surface immunoglobuli ns, and potentiates the response to other inducers such as LPS or IL-1 . In the present study we investigated whether NF-kappa B activation w as related to the MDP-stimulated immunoglobulin expression. In a gel s hift assay our results confirmed that MDP but not MDP(D,D), an adjuvan t-inactive stereoisomer, could induce a kappa B-binding activity in 70 Z/3 cells. The LPS or IL-1 induced NF-kappa B binding activity was inc reased in the presence of MDP but not of MDP(D,D). A mutant of the cel l line called 1.3E2, defective in NF-kappa B activations by LPS, did n ot respond to MDP. The enhanced surface immunoglobulin expression indu ced in the wild type 70Z/3 cells by MDP alone or combined to LPS, IL-1 or IFN gamma, was not obtained in this variant. The ability of variou s treatments to activate the kappa gene enhancer was quantitatively ev aluated in cells transfected with a kappa-enhancer-luciferase expressi on plasmid. Treatment of transfected 70Z/3 cells with MDP resulted in a dose-dependent enhancement of luciferase activity, an additive effec t to that induced by LPS or IL-1. Treatment of the defective variant t ransfected with the same construct did not result in luciferase expres sion after stimulation with the various agents. The transient transfec tion assays were used to compare the effectiveness of some MDP analogs . Two adjuvant-active compounds unable to enhance kappa light chain ex pression did not increase the basal response in the transfected 70Z/3 cells, indicating that NF-kappa B activation was not related to the ad juvant potency of MDP but correlated with the kappa induction.