CD proteins, also known as Cluster of Differentiation proteins, are cell surface molecules that play a fundamental role in the identification, classification, and functional regulation of immune cells. These proteins are widely used as biological markers in immunology to distinguish different cell populations and study immune system activity.

They are essential for processes such as cell signaling, immune activation, antigen recognition, and communication between immune cells. Different CD proteins are expressed on specific cell types, making them highly valuable for research and clinical diagnostics.

CD proteins are commonly analyzed through laboratory techniques such as flow cytometry, immunohistochemistry, and ELISA-based assays. Their study is critical in understanding immune responses, cancer progression, autoimmune disorders, and infectious disease mechanisms.

Due to their importance in cellular identification and disease research, CD proteins continue to be a major focus in immunology, molecular biology, and therapeutic development.