Polyreactivity of human monoclonal antibodies: Human IgM anti-rhesus monoclonal antibodies are frequently polyreactive

The aim of this study was to characterize human anti-Rhesus monoclonal antibodies cross-reacting with tissue antigens. Of the 155 monoclonal alloantibodies tested, 49 also reacted with intracellular antigens, as demonstrated by immunofluorescence assay on cryostat sections of animal and human tissues. This cross-reactivity was mainly a property of monoclonal alloantibodies belonging to the IgM isotype (among the 49 cross-reacting Mabs, 37 were IgM). The results confirm that during an immune response against a foreign antigen (alloantigen), B cells that produce polyreactive antibodies are not excluded from the pool of responding cells.