If an antbody that was formed to react with a specific virus also attacks liver cells, that is an example of Sperm celis are not normally exposed to blood, but if they are, the immune system may produce against sperm cells' and render someone sterile. The immune system mav oroduce antibodies against self-antigens that were by a drug or viral infection. It seems all people have T cells that have the capability to produce autoantibodies, but keep them in check to prevent diseases..