Used in immunological research and diagnostic assays to detect and quantify CD5-expressing cells, particularly T cells and a subset of B cells (B1a cells). Employed in flow cytometry, immunohistochemistry, and Western blotting to study immune cell populations and their roles in autoimmune diseases, chronic lymphocytic leukemia (CLL), and other lymphoproliferative disorders. Serves as a reference standard in antibody development and validation due to its well-characterized binding properties. Also utilized in therapeutic antibody screening and as a control in clinical diagnostics to ensure assay accuracy and reproducibility.