I have vaccinated mice and harvested serum from these mice. When the vaccinated serum is mixed with the target antigen and applied to cells in culture, it actually increases the death of the cells vs. control. It is like there is some kind of immune reaction (complement-mediated, antibody-antigen complex formation?) which is promoting the death of the cells vs. neutralizing the antigen and protecting these cells as would be expected. Has anyone seen this before and how did you troubleshoot?