Broad dispersion and lung localization of virus-specific memory B cells induced by influenza pneumonia.

Although memory B cells (B(Mem)) contribute significantly to resistance to infection, B(Mem) population characteristics that may relate to protective efficacy have received little attention. Here, we report a comprehensive quantitative analysis of virus-specific IgG and IgA B(Mem) dispersion after transient influenza pneumonia in mice. From early in the response, B(Mem) circulated continuously and dispersed widely to secondary lymphoid tissues. However, a complicated picture emerged with B(Mem) frequency differences between secondary lymphoid tissues indicating an influence of local tissue factors on trafficking. B(Mem) numbers increased and stabilized at tissue-specific frequencies without contraction of the B(Mem) pool during the period of analysis. The lung was notable as a nonsecondary lymphoid tissue where a rapid influx of IgG and IgA B(Mem) established relatively high frequencies that were maintained long term. Our findings provide insights into the pattern of B(Mem) dispersion, and emphasize the lung as a complex repository of immune memory after local infection.