Adjuvant-independent immunization by immunotargeting antigens to MHC and non-MHC determinants in vivo.

Using avidin as a model protein antigen, and biotinylated monoclonal antibodies as a convenient means of forming stable complexes with avidin, we have investigated the adjuvant-independent immunization of three mouse strains, C57BL/6, C3H and (C57BL/6 x C3H)F1, with immunoconjugates targeted to different class II MHC and non-MHC sites. The results confirm the effectiveness of anti-I-Ak and anti-I-Ab immunoconjugates with respect to priming for secondary IgG responses in (H-2b x H-2k)F1 mice, while indicating a lack of response in strains which are homozygous for the targeted allele. In terms of non-MHC targets in the monocyte-macrophage lineage, neither anti-MAC-1 nor anti-MAC-2 immunoconjugates were effective in any of the three strains. However, the 33D1 anti-dendritic cell antibody gave significant responses in all three strains, with the F1 response being more than 10-fold greater than the anti-class II immunoconjugates in either strain. These findings indicate that immunotargeting a protein antigen to a non-MHC determinant on dendritic cells in vivo can be an effective means of inducing an adjuvant-independent serological response, and that this approach can have significant advantages over anti-class II MHC immunotargeting.