Arylsulfatase in natural killer cells: its possible role in cytotoxicity.

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Abstract
Ultrastructural cytochemistry of [human] natural killer cells enriched by Percoll gradient centrifugation showed them to possess arylsulfatase (aryl-sulfate sulfohydrolase, EC 3.1.6.1). The enzyme was located in vesicles, granules and the parallel tubular arrays, organelles characteristic for cytotoxic lymphocytes. Biochemically, peak enzyme activity correlated with the Percoll fractions containing cells with cytotoxicity for melanoma target cells. Treatment of natural killer cells with Na2SO4, a competitive inhibitor of arylsulfatase, suppressed cytotoxicity by almost 50%. EM of effector-target cell conjugates, which had been permitted to incubate for only 30 min, disclosed numerous arylsulfatase-positive sites at the points of contact between the effector/target cell membranes. The enzyme was translocated to the surface before lysis of the target cell was morphologically evident. The parallel tubular arrays probably play a role in this translocation. Arylsulfatase may function in the degradation of cerebroside sulfate ester components of the target cell membrane to initiate the lytic event.