Used in immunological research to detect and quantify CD69 expression on immune cells, particularly during early activation of T cells, B cells, and natural killer cells. Employed in flow cytometry and immunohistochemistry to study immune responses in diseases such as autoimmunity, transplantation, and cancer. Serves as a reference standard in the development of diagnostic assays and therapeutic antibodies targeting the CD69 pathway. Also utilized in functional studies to block CD69-mediated signaling, helping to elucidate its role in inflammation and lymphocyte regulation.