Figure 3. CD27^lo cells produce activation-induced cytidine deaminase (AICDA, AID).

AICDA and EXO1, which have been implicated in somatic hypermutation and class-switch recombination, have more abundant mRNA levels in CD27^lo cells. This suggests that the cells may be undergoing receptor editing. IL2RA was also expressed at higher levels by CD27^lo cells. CCL22, CD80, and BCL2L11 were also expressed at higher levels in CD27^lo cells than in CD27^hi or in undivided cells (n = 6 subjects, SAM analysis q values in Supplementary Table 1). (†) at least one probe significantly different between CD27^lo and CD27^hi at FDR = 0.03, SAM analysis, (*)CD27^lo/Undivided, at least one probe significant, FDR = 0.01, (**)CD27^lo/undivided at least one probe significant at FDR = 0.008. (b) AICDA, IL2RA, and CCL22 mRNA levels were confirmed by qRT-PCR. CCL22 levels between CD27^hi and undivided cells were not significantly different (n = 10 subjects, paired T-test p values in Supplementary Table 2). The point in each violinplot is the median value and the brackets indicate the interquartile range. AID protein was expressed in higher levels in divisions 1 and 2, where CD27^lo cells predominate. Representative data from 1 subject shown, n = 4 subjects in 2 separate experiments. (c) Gene array analysis showed that while AICDA, IL2RA, and EXO1 were more abundant in CD27^lo cells, many other germinal center markers were at higher levels in undivided cells. Naïve cell markers CD5 and ABCB1 were not expressed in amounts that would indicate naïve cell contamination. (d) Expression levels of 7 GC-associated genes were confirmed by qRT-PCR.