The term "autoreactive" describes immune cells or molecules that react against the body's own tissues. Some synonyms for this term include "self-reactive," "self-antigen-specific," or "autoaggressive." These terms reflect the fact that the immune system is designed to distinguish between self and non-self antigens, and that autoreactive immune responses can lead to autoimmune diseases such as type 1 diabetes, multiple sclerosis, or rheumatoid arthritis. Understanding the mechanisms that lead to autoreactivity, including defects in immune tolerance or aberrant antigen presentation, is therefore crucial for the development of new therapies that can target specific immune cell populations or reduce inflammation in affected tissues.