Non-covalent alpha2M-peptide complexes are immunogenic and can protect mice from a tumor challenge. (A) Protein-peptide complexes were prepared as described and injected into mice intradermally on days -14 and -7. Mice were challenged with live tumor cells on day 0 and tumor growth was monitored. (B) alpha2M or gp96 was complexed with synthetic ova20 peptide containing the CTL epitope of OVA. Mice were challenged with B16-F10 transfected with OVA. The fractions in the top left corner of each panel correspond to the number of mice surviving past day 22. (C) alpha2M, gp96 or albumin was complexed to a preparation of Meth A tumor-derived peptides (MethA10) as described in Materials and methods. Mice were challenged with Meth A. In B and C control mice were injected with uncomplexed alpha2M or gp96, with peptide alone or with PBS.