Comparison of immune responses induced by rat RT-1 antigens presented as inserts into liposomes, as protein micelles and as intact cells.

Partially purified rat transplantation antigens (RT-1) were inserted into liposomes composed of various types of lipids and used for immunization. The immune responses induced by the liposomes were compared with responses induced by RT-1 as protein micelles, alone or emulsified in Freund's incomplete adjuvant, or intact cells. Liposomes gave generally a higher humoral response than protein micelles. Each type of RT-1 immunization gave a particular pattern of specific Ig (sub)class responses. Freund's incomplete adjuvant was not only lacking in potentiating effect on low protein dose immunization but had a significant inhibitory effect. Besides intact cells only distearoyl-phosphatidylcholine liposomes had the potential to induce a cell-mediated cytotoxic response.