Figure 6.

Reduced somatic hypermutation in activation-induced deaminase (AID) heterozygotes in the absence of selection. Peyer's patches were collected from AID wild-type (WT) and heterozygous (Het) MRL/lpr mice at 8, 12 and 16–18 weeks of age (n= 6, n= 6 and n= 18, respectively). Peyer's patches from mice with the same genotypes and ages were pooled for the 8- and 12-week-old age groups but not the 16- to 18-week-old mice, in which mice were analysed individually. B220⁺ CD19⁺ GL7⁺ cells were sorted and lysed for DNA preparation. A 1·2-kb fragment from the intronic region 3′ of the rearranged endogenous V_H genes was amplified by polymerase chain reaction and cloned for DNA sequencing. Totals of 46 (8 weeks), 40 (12 weeks), and 179 (16–18 weeks) sequences were analysed with approximately the same number of clones for heterozygotes and wild-type mice. The mutation frequency was calculated among all clones (mutations per clone) and among only those clones that were mutated at least once (mutations per mutated clone). Error bars represents standard errors.