Anti-hCD10 recognizes a human common acute lymphoblastic antigen (CALLA), MW 100 kDa. The CD10 antigen is identical to human membrane-associated neutral endopeptidase (NEP;EC 3.3.24.11), also known as enkephalinase. The CD10 antigen is found on lymphocytes from patients with acute B-lymphoid leukemia. The antigen is also present on a wide variety of normal and neoplastic cell types including renal epithellum, fibroblasts, granulocytes and some lymphoma, melanoma and glioma cell lines. Identification of CD19 PE human B cells associated approximately 10% of peripheral blood lymphocytes expressing the 95,000 M.W. surface antigen.