Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In fact, as it has been previously demonstrated in many different studies, peripheral blood lymphocytes are hosts to viral replication (14-17), while granulocytes may be passively carrying the different forms of HBV DNA as a result of their phagocytic activity on dead hepatocytes in the liver.
Category: