Biological systems are dynamic, but predominant reductionist approaches in biology model these systems with little context of other related systems. Peircean semiotics is a methodology that models a pathway in reference to other levels of organization. In this study, immune response of deer mice infected with Sin Nombre Virus (SNV) is modeled using Peircean semiotics. Results suggest the immune systems of deer mice adopt the virus as a part of self, ultimately saving the mice from the inappropriately excessive inflammatory response (Hantavirus cardiopulmonary syndrome, HCPS) that kills humans infected with SNV. This work supports Peircean semiotics as a biological methodology when applied to cellular mechanisms and suggests an immunosuppressive vaccine may be effective for preventing HCPS in humans.