CD11c is a type I transmembrane glycoprotein of approximately 150 kDa, also known as integrin alpha X (Itgax). It is part of the complement receptor 4 (CR4) complex and, along with CR3 (also known as Mac-1 or CD11b/CD18), belongs to the β2-integrin family of adhesion molecules. CD11c is primarily expressed on dendritic cells (DCs), NK cells, a subset of intestinal intraepithelial lymphocytes (IELs), and some activated T cells. It is involved in cell adhesion, migration, and phagocytic functions, mediating the phagocytic process of DCs through its association with β2-integrin. Under conditions of early development and in certain neurodegenerative diseases such as Alzheimer's disease (AD), a subset of microglia in the central nervous system also expresses CD11c. CD11c+ microglia express genes such as Spp1, which encodes osteopontin (OPN), a cytokine-like phosphorylated protein involved in pathogenic and protective immune responses in peripheral lymphoid tissues. Additionally, CD11c serves as a marker for macrophages, whose expression aids researchers in identifying and characterizing these cells, thus contributing to a deeper understanding of their roles in immune and inflammatory processes.