In response to viral infection, the immune systems of mice typically produce antibodies that destroy the virus by binding to proteins on its surface  Mice infected with the herpesvirus generally develop keratitis, a degenerative disease affecting part of the eye
Since proteins on the surface of cells in this part of the eye closely resemble those on the herpesvirus surface, scientists hypothesize that these cases of keratitis are caused by antibodies to the herpesvirus
Mice that are infected with the herpesvirus but do not develop keratitis produce as many antibodies as infected mice that do develop keratitis