The Journal of Immunology, Vol 154, Issue 5 2041-2050, Copyright © 1995 by American Association of Immunologists

ARTICLES

Mitogen activation of a nuclear alkaline phosphatase in normal activated lymphocytes

AL Kenter and L Morgan
Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago 60680.

B cell differentiation is punctuated by V(D)J joining in the heavy chain of the pro-B cell, VJ joining in the light chain of the pre-B cell, switch recombination, and somatic hypermutation in the mature B cell. The regulatory signals controlling these events and the developmental program leading to them is poorly understood. We have identified a new phosphatase activity that is expressed in lymphocytes and for which high expression is restricted to mature B cells. This new phosphatase is transiently expressed in nuclear extracts of mitogen- activated splenic B cells. The phosphatase is a monoesterase that is active on both dNMPs and pNPP. The phosphatase has been partially purified by column chromatography and is inhibited by orthovanadate, molybdate, tetramisole, and EDTA and requires Mn2+ for activation. Monoesterase activity requires a pH above the neutral range. The activity profile in the presence of the inhibitors and the requirement for basic pH suggest that this enzyme is an alkaline phosphatase.

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