Polyclonal B cell activation in infections: infectious agents’ devilry or defense mechanism of the host?

Polyclonal B cell activation is not a peculiar characteristic to a particular infection, as many viruses, bacteria, and parasites induce a strong polyclonal B cell response resulting in hyper‐γ‐globulinemia. Here, we discuss the different roles proposed for polyclonal B cell activation, which can be crucial for early host defense against rapidly dividing microorganisms by contributing antibodies specific for a spectrum of conserved structures present in the pathogens. In addition, polyclonal B cell activation can be responsible for maintenance of memory B cell responses because of the continuous, unrestricted stimulation of memory B cells whose antibody production may be sustained in the absence of the antigens binding‐specific BCR. Conversely, polyclonal activation can be triggered by microorganisms to avoid the host‐specific, immune response by activating B cell clones, which produce nonmicroorganism‐specific antibodies. Finally, some reports suggest a deleterious role for polyclonal activation, arguing that it could potentially turn on anti‐self‐responses and lead to autoimmune manifestations during chronic infections.