While the immune system has developed to eliminate foreign pathogens, the principles underlying self-recognition are not fully understood. It has been recently acknowledged that self-reactivity is not necessarily detrimental; instead, it can provide beneficial outcomes for the host. Indeed, innate and acquired immune receptors broadly recognize self components, thereby sensing the perturbation of host equilibrium to drive homeostatic responses. In particular, we found that receptor families lying between innate and acquired immunity, such as ITAM-coupled innate receptors and unconventional TCRs, recognize various host-derived metabolites. In this meeting, I will present our recent study on self-recognition via CD1d-restricted iNKT cells and discuss its physiological relevance in immune homeostasis.