A dual role for B cells in Plasmodium chabaudi chabaudi (AS) infection?

CD4+ T cells are necessary for a protective immune response against the erythrocytic stages of the malaria parasite Plasmodium chabaudi chabaudi AS. B cells are not required for control of early acute parasitaemias, but appear to be important for final clearance of the infection, most probably by producing specific antibodies against the parasite. However, immune sera and immune IgG are unable to replace the protective capacity of B cells in adoptive transfer of immunity to P. chabaudi AS. It is therefore conceivable that B cells are required to achieve protective immunity, not only as effector plasma cells, but because they may also play a second important role. We have recently suggested that B cells may regulate the Th response to P. chabaudi AS during a primary infection. We discuss here the possibility of a dual requirement of B cells in achieving protective immunity to P. chabaudi AS.