Adaptive B Cell Responses to Influenza Virus Infection in the Lung.

Adaptive B cell response is a key arm of protective immunity against influenza viruses. Owing to the acutely infectious and cytopathic nature of these viruses, efficient containment of viral spread relies on the prompt provision of protective antibodies to the site of virus infection, the respiratory tract (RT). To accelerate the protective antibody response, B cell responses can be ectopically induced, maintained, and reactivated in the lungs after primary and secondary infection, thereby providing an anatomical advantage in supplying neutralizing antibodies against reinfecting viruses with faster kinetics. However, the prompt supply of protective antibodies may be insufficient to protect against reinfection because influenza viruses can easily change their antigenic profiles to escape antibody surveillance. B cell responses have multiple strategies for adjusting antibody repertoires according to viral fitness, one of which is the formation of local germinal centers capable of selecting B cell repertoires for antigenically subdominant, but conserved, epitopes. In this review, we discuss several unique aspects of B cell responses that take place at local sites to combat acutely infectious and rapidly mutating influenza viruses.