The considerable variability of responses amongst subjects to disease triggers and immunotherapies is a major obstacle to designing better immune-based therapies. Therefore, development of patient-tailored precision medicine that improves the efficacy of immunomodulatory drugs is necessary. The individualized response to disease triggers and immunomodulatory therapies was studied using the concanavalin A (ConA) immune-mediated hepatitis model and the oral administration of anti CD3 or β-glucosylceramide (GC). Mice were treated with anti-CD3 antibodies or GC followed by an injection of ConA. The effects of these treatments on liver damage and the immune profile were then analyzed. An individualized response to ConA and orally administered immunomodulatory agents was observed in eight consecutive experiments. While alleviation of the immune-mediated liver injury, as measured by serum levels of liver enzymes, was seen, and high intra-group and inter-experimental variabilities were detected. A similar individualized response was observed for the effect on serum levels of IFN-γ, TNF-α, and IL-10 and on CD4+CD25+, CD8+CD25+, and CD3+NK1.1+ lymphocytes. A personalized form of inherent randomness in an isolated system was documented, which may underlie the variability in responses to immune triggers and immunomodulatory therapies. The data support the use of personalized randomness-based platforms for improving the response to chronic therapies.