This chapter conceptualizes the Transport-in-All-Policies (TiAP) approach through the lens of Urbanimmunology, interpreting transport as the life-sustaining and protective system of cities and society. It frames policy integration as an immune response, where non-transport sectors recognize, adapt to, and coordinate with transport functions to maintain systemic health. Through the metaphor of systemic mobilities, transportation is depicted as the metabolism of cities and society—circulating resources, regulating exchanges, and sustaining resilience across social, environmental, cultural, and virtual domains. At the individual level, the cellular self illustrates how transport underpins everyday vitality, while the urban immune system translates these dynamics into the physiology of the “HEARTY” city—Healthy, Ecological, AI-driven, Resilient, Tourism-friendly, and Yearning. Finally, the urban immune code reinterprets TiAP principles by matching with Urbanimmunological laws, and the urbanimmune diagnosis identifies policy pathologies that hinder systemic integration, proposing pathways toward robust, adaptive, and regenerative transport governance.