Generation of IgA plasma cells during a secondary response in the absence of IgA memory B cells (LYM6P.800)

Abstract

Abstract IgA antibodies are important for protection against infection at mucosal surfaces. Despite this importance in protective immunity, the differentiation of IgA B cells is not well understood. To address this issue, an antigen-based enrichment method was used to track polyclonal B cells specific for the model antigen R-Phycoerythrin (PE) during the course of a T-dependent immune response. While 10-40% of the PE-specific short lived plasma cells expressed IgA, less than 0.05% of the PE-specific germinal center and memory B cells expressed IgA. Despite the lack of IgA memory B cells, secondary antigen challenge resulted in the generation of large numbers of PE-specific IgA plasma cells that appeared at times prior to the appearance of IgA plasma cells during the primary response. Since IgA memory B cells were infrequently detected, we hypothesize that IgA plasma cells generated during the secondary challenge are the result of a secondary switch from memory B cells expressing other isotypes. We are currently examining the role that individual isotypes of memory B cells play in the generation of IgA plasma cells by looking for IgG switch remnants in the PE-specific IgA plasma cells generated after secondary challenge, and by testing the ability of purified isotypes of memory B cells to produce IgA plasma cells after transfer and challenge of recipient mice.