Peer Review became adversarial in the 1980s in Patrick v. Jay.
a.    Dr. Patrick sued his colleagues for anti-trust violations.  SC focused on due process issues.  Court said not a private issue, but a state issue, so entitled to due process.
b.    Responsibility for overseeing quality of care of hospital is up to the state.  This is a quasi-state action.  Dr. Patrick was thus entitled to due process.
c.    Dr. Patrick sued both the hospital and the individual doctors.