starting to act on their immunological system

starting to act on their immunological system = starting to act on the cells' immunological system?

Context:

New Cellular 'Armor' Developed to Prevent Infection by AIDS Virus
ScienceDaily (July 31, 2010) — Research by the Consejo Superior de Investigaciones Científicas (CSIC) and led by Mr Félix Goñi, director of the Biophysics Unit at the CSIC-University of the Basque Country Mixed Centre, has led to the development of a novel method of attack against the AIDS virus. The method involves creating a prevention system, i.e. an 'armour' in the cells that are likely to be infected and thus impede the virus from accessing them and starting to act on their immunological system.