Human Early Activation Antigen CD69 (CD69) Protein

Background

CD69, also known as activation inducer molecule (AIM), is a type II transmembrane glycoprotein expressed primarily on the surface of activated immune cells, including T cells, B cells, natural killer (NK) cells, macrophages, and dendritic cells. CD69 is one of the earliest surface markers to be upregulated after lymphocyte activation, making it a widely used marker of immune cell activation. Its expression can be induced by a variety of stimuli, including antigen recognition, cytokines, and inflammatory signals. In addition to its role in immune activation, CD69 also plays critical roles in immune homeostasis, inflammation regulation, and tissue retention of lymphocytes. It functions as a key regulator of immune responses, particularly through its involvement in the migration and localization of immune cells to sites of inflammation or infection. Furthermore, CD69 is important in maintaining tissue-specific immunity in organs such as the lungs and intestines, where resident immune cells contribute to mucosal defense.