Neuraminidase alteration of human lymphocyte reactivity to mitogens, antigens and allogenic lymphocytes.

Lymphocyte reactivity to phytohemagglutinin (PHA) was reduced significantly in whole-blood cultures initiated with nontoxic concentrations of Vibrio cholerae neuraminidase (VCN). Reduced responsiveness was not due to degradation or inactivation of PHA by this enzyme, and the reaction was dependent upon the dose and time at which this mitogen and enzyme were added to the cultures. In cultures from some subjects, VCN also inhibited reactivity to concanavalin A. In contrast, lymphocyte reactivity to mitogens from pokeweed or Staphylococcus aureus as well as to antigens or allogeneic lymphocytes was enhanced by VCN. At concentrations required to elicit these effects, VCN itself was not stimulatory.