Increase in titer of the naturally occurring human antibody to neuraminidase-treated lymphocytes after influenza.

Nine of 25 (36%) humans suffering from naturally acquired influenza A infection developed significant increases in the titer of a "naturally" occurring antibody to neuraminidase-treated human lymphocytes. Only two of 43 normal and noninfluenza respiratory infection controls showed titer changes of this antibody, p less than 0.001. The antibody was not directed at influenza virus C fixation, hemagglutination inhibition, or neuraminidase antigens. Three of 10 normals given a highly immunogenic, formalin-killed influenza A vaccine developed significant titer rises. These results suggest that influenza virus, live or dead, can provoke an increase in antibody to a cross-reacting antigen present on neuraminidase-treated human lymphocytes.