Activity of human IgG and IgA subclasses in immune defense against Neisseria meningitidis serogroup B

Both IgG and IgA Abs have been implicated in host defense against bacterial infections, although their relative contributions remain unclear. We gener ated a unique panel of human chimeric Abs of all human IgG and IgA subclass es with identical V genes against porin A, a major subcapsular protein Ag o f Neisseria meningitidis and a vaccine candidate. Chimeric Abs were produce d in baby hamster kidney cells, and IgA-producing clones were cotransfected with human J chain and/or human secretory component. Although IgG (isotype s IgG1-3) mediated efficient complement-dependent lysis, IgA was unable to. However, IgA proved equally active to IgG in stimulating polymorphonuclear leukocyte respiratory burst. Remarkably, although porin-specific monomeric , dimeric, and polymeric IgA triggered efficient phagocytosis, secretory Ig A did not. These studies reveal unique and nonoverlapping roles for IgG and IgA Abs in defense against meningococcal infections.