Recruitment of a distinct but related set of VH sequences into the murine CD21hi/CD23- marginal zone B cell repertoire to that seen in the class-switched antibody response.

Development and maintenance of cells in the murine follicular and marginal zone compartments is thought to involve differing levels of stimulation of the BCR, although it is still not clear which BCR ligands mediate these events. How the delineation between naive and Ag experienced B cell populations relates to cell phenotype and how precise or blurred this delineation is, is also not well understood. In this study, using PCR to analyze the Ab response to phenyl-oxazolone in the mouse, we show that the Ab repertoire of CD21(hi)/CD23(-) marginal zone B cells shows persistent increase in levels of particular IgM after immunization with foreign Ag. Further, we show that these IgMs have different but related VH/CDR3 sequences from those seen in the class-switched response to oxazolone that we have also analyzed. We also detect an effect of Ag on the follicular B cell repertoire that is less persisting. These results provide evidence consistent with the signal-strength model of mature B cell development being extended to include stimulation by foreign Ag, and also further the known zone of influence of foreign Ag on the B cell compartment.