Influenza A viruses cause annual epidemics and occasionally pandemics. Antibodies directed to the conserved viral nucleoprotein (NP) may play a role in immunity against various influenza A virus subtypes. Here, we assessed the immunological significance of a human monoclonal antibody directed to NP in vitro. This antibody bound to virus-infected cells but did not display virus-neutralizing activity, complement-dependent cell cytotoxicity, or opsonization of viral antigen for improved antigen presentation to CD8(+) T cells by dendritic cells.