Characterization of immunogenic properties of haptenated liposomal model membranes in mice. VII. Synergistic responses to haptenated liposomes and haptenated thymus-dependent antigens in CBA/N mice.

CBA/N mice have an X-linked B-cell defect which prevents them from responding to non-mitogenic thymus-independent (TI-2) antigens such as haptenated Ficoll. The CBA/N mice do, however, respond to another group of thymus-independent (TI-1) antigens among which are haptenated liposomes. The F1 male progeny of CBA/N female mice express the same characteristics. Hapten-specific plaque-forming cell (PFC) responses to haptenated proteins (thymus-dependent, TD, antigens) by CBA/N mice and CBA/N x C3H/HeN F1 male mice can be blocked by concomitant exposure to TI-2 antigens bearing the same hapten. Simultaneous exposure to haptenated liposomes (TI-1 antigen) and TD antigens, however, results in a synergistic response to the hapten if the antigens share common epitopes. The tripeptide-enlarged hapten dinitrophenyl-beta-alanylglycylglycine (J), conjugated to phosphatidyl-ethanolamine (PE) and incorporated into liposomal model membranes, was used throughout the experiments. In F1 male mice the moderate responses to TD antigens could be restored to values equivalent to those seen in F1 female mice. This adjuvant effect of haptenated liposomes is hapten-specific, time-dependent, and restricted to certain structural forms of the liposomes.