CD44H is the standard isoform of the CD44 protein, a widely expressed cell surface glycoprotein that plays a crucial role in cell adhesion, migration, and interaction with the extracellular matrix. It is the most common form of CD44, encoded by exons 1鈥?, 16, 17, and 19, and lacks the variable exons that characterize other CD44 isoforms. CD44H is expressed in various cell types, including immune cells and cells of the central nervous system. It primarily functions through binding to hyaluronic acid (HA), facilitating cell adhesion, and mediating cellular responses to the extracellular environment. This standard form is essential for maintaining tissue integrity and regulating cell behavior in both physiological and pathological conditions.