Neutral maltase: the first human B-cell enzymatic marker reflecting terminal differentiation of mature B cells into plasma cells.

Neutral maltase activity (alpha-D-glucoside glucohydrolase; EC: 3.2.1.20) was measured in B and T lymphocytes from peripheral blood of normal subjects and patients suffering from chronic or acute lymphoid leukemias. Neutral maltase activity is undetectable in T cells from normal subjects as well as in patients with chronic or acute T-lymphoid leukemias. Conversely, whereas this enzyme activity is always undetectable in chronic or acute B-lymphoid leukemia, neutral maltase activity is expressed in mature B cells from normal subjects. The detection of higher neutral maltase activity in plasma cells from myelomas than in normal B cells supports the concept that the expression of neutral maltase activity is related to the stages of differentiation and maturation reached by lymphocytes of the B-cell lineage. Neutral maltase therefore appears as the first B-cell enzymatic marker described that is expressed in the course of terminal differentiation of mature B cells into plasma cells.