Dendritic cells (DCs) are the primary response cells mediating the progression from innate to adaptive immunity and the induction of self-tolerance. Type 1 interferons (IFNs) play an essential role in both the DC antiviral response and cause dramatic changes in the expression patterns of many interferon-induced genes. The RIGI protein (gene DDX58) activation acts as a sensor of viral intrusion, leading to activation of the IFNB1-DDX58 loop. Interferon ? is secreted into the extracellular medium, where it binds in an autocrine and paracrine fashion to IFN cell surface receptors on the secreting cell and on neighboring cells respectively. This binding activates DDX58 gene and leading to RIG-I production. In infected cells, the newly induced RIG-I become activated and lead to IFNB1 induction, thus completing the IFNB1-DDX58 loop.

DDX58 is significantly induced in virus-infected DCs two to three hours before IFNB1 is. We developed an agent based model (ABM) that simulates the important part of the IFNB1-DDX58 positive feedback loop in order to show that small early amount of IFNB1 mRNA present in a population of cells, hides the existence of a subset of early responder cells reacting strongly to the infection.

The simulation emulates a portion of a medium with both infected and uninfected DCs. The extracellular model is two dimensional, and the medium is represented by a square lattice, where each lattice square has the size of a single cell. Each cell is simulated as an independent agent, where the agents interface through the extracellular medium. The graphical display engine generates an animation by depicting the state of the simulated area at each simulation step.