Source of CXCL13 in the thymus of MG patients. (A) Correlation between CXCR5 and CD21 mRNA levels (i), CXCL13 and CD21 mRNA levels (ii), and CXCL13 and CXCR5 mRNA levels (iii) in samples from MG untreated patient thymuses. The R2 and P value were obtained by the nonparametric correlation test (Spearman test). (B) Amplification of CXCL13 gene by real-time RT-PCR on total sections from 6 adult controls (Ctl1-6), 5 thymic GC-free sections from untreated MG patients (MG1-5), and their corresponding microdissected GCs. RT-PCR was performed in duplicate. Error bars represent the mean value of the 2 duplicates ± SEM.