Figure 6.

Qβ-specific isotype-switched PNA^low B cells exhibiting a partial plasma cell phenotype are absent in Cr2^−/− mice. (A) Expression of CD138, VLA-4, LFA-1, and CD44 on Qβ-specific PNA^low and PNA^high B cells from WT mice. B220⁺ splenocytes were purified by magnetic cell sorting; IgM^lowIgD^low B cells binding Qβ and low or high levels of PNA were gated and analyzed for expression of the indicated surface markers. One of three similar experiments is shown. (B) Comparison of CD138, VLA-4, LFA-1, and CD44 expression on Qβ-specific PNA^low and PNA^high isotype-switched B220⁺ splenocytes from Cr2^−/− and WT mice on day 12 after immunization. (C) Phenotype of Qβ-specific B cells in the blood of WT mice on day 12 after immunization. PNA-binding on Qβ-specific (IgM; IgD; CD4; CD8; CD11b; Gr-1; YO-PRO-1)⁻B220⁺ cells was determined. Expression of cytoplasmic Ig in Qβ-specific PNA^low B cells was assessed by analysis of binding of Alexa647-labeled Qβ to permeabilized (CD4; CD8; CD11b)⁻B220^low cells.