Activity and isoenzymes of acid phosphatase in human B-cell lymphomas of low-grade malignancy: a novel aid in the classification of malignant lymphoma.

Activity and isoelectric focusing (IEF) pattern of lysosomal acid phosphatase (E.C.3.1.3.2.) were investigated in 55 cases of low-grade malignant B-cell lymphoma, classified as chronic B-lymphocytic leukemia (B-CLL), centroblastic/centrocytic follicular lymphoma (CB/CC), lymphoplasmacytic/lymphoplasmacytoid lymphoma (Immunocytoma, IC), and plasmacytoma (PC), applying the criteria of the Kiel classification. The results show (1) that the four lymphoma types present a characteristic range of enzyme activity in an increasing order: B-CLL, BC/CC, IC, and PC. B lymphocytes, germinal center cells, and plasmacytes are the main constituents of these lymphomas. This sequence might reflect one possible mode of B-cell transformation into plasmacytes traversing an amplification stage in germinal centers under normal conditions. (2) All cases showed the basic IEF pattern of normal B lymphocytes with 12 bands localized in three regions between pH 6.1 and 3.9. This finding supports the B-cell origin and the close phenotypical relationship among the investigated lymphomas. (3) The IEF patterns of B-CLL and CB/CC did not differ from that of normal B lymphocytes, whereas two additional isoenzymes were encountered in cases of IC and seven in PC; this suggests that the higher enzyme activity of IC and PC is at least partly due to the appearance of "new" isoenzymes. The results support the validity of the underlying classification and indicate the individually, B-cell origin, and close relationship among the four lymphoma entities investigated.