ISCOMS CONTAINING PURIFIED QUILLAJA SAPONINS UP-REGULATE BOTH TH1-LIKE AND TH2-LIKE IMMUNE-RESPONSES

The immune stimulating complex (iscom) is built up by antigen, cholest erol, phospholipids, and adjuvant active Quillaja saponins. Previous s tudies have shown that iscoms containing Quil A (a semipurified prepar ation of saponins) efficiently induce antibody and cell-mediated immun e responses. In this study, we demonstrate that iscoms containing a mi xture of two purified low toxicity Quillaja saponin fractions (ISCOPRE P 703) are able to upregulate both Th1-like and Th2-like immune respon ses. Thus, ovalbumin (OVA) iscoms induced higher levels of antigen-spe cific IgG1 and IgG2a antibodies and increased the production of both I FN-gamma and IL-4 compared with OVA administered without adjuvant, In contrast, OVA formulated in Al(OH)(3) elicited IgG1 and IgE antibodies and primed spleen cells producing IL-4 and IL-10, suggesting the acti vation of primarily Th2-like cells. These findings underline that adju vants are able to alter the character of immune responses and may be u sed to generate responses with desired properties. (C) 1997 Academic P ress.