The Immunopotentiating Property of Lipophilic Muramyl Dipeptide and Its Molecular State in Liposomal Membranes: Plaque-Forming Cell Responses and ESR Studies

Abstract

The immunopotentiating property of spin-labeled lipophilic muramyl dipeptide (SL-MDP) in liposomes was studied as to the plaque-forming cell (PFC) response to glycophorin, as an antigen, in membranes. The effect of SL-MDP depended on the densities of both SL-MDP itself and the antigen. The addition of the optimal amount of SL-MDP to liposomes containing a low density (0.016 mol%) of the antigen increased the PFC response by three times, whereas the presence of SL-MDP in optimal antigen density (0.032-0.127 mol%) membranes was rather inhibitory. In these liposomes, the amounts and molecular states of SL-MDP were determined from ESR spectra and are discussed in connection with its immunopotentiating property.