(A) Detailed gating strategy of memory B cells. (B) The percentage and total number of AID+ splenic B cells was not significantly different between the experimental and control naïve groups (p>0.05). (C) Mice receiving CTLA4-Ig from day 7 demonstrated reduced percentage and total number of I-Ed-specific AID+ memory B cells at day 42 postimmunization, compared to untreated sensitized mice. In contrast, delayed treatment with CTLA4-Ig from day 14–42 failed to show the significance when compared with no treatment sensitized mice. (C) Naïve and C57BL/6 mice at >10 weeks post-BALB/c heart transplant, the majority of AID+ B cells, for both bulk and I-Ad-specific, were CD73+CD273+, whereas AID− B cells were CD73−CD273−. Each dot represents an individual mouse, data are presented as mean ± SD, and statistically significant differences are indicated (**p<0.01).