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.