Comparative analysis of FcRH1 expression by different subpopulations of tonsillar B lineage cells. (A) Mean fluorescent intensity (MFI) of cell surface FcRH1 (± 1 SD) is shown for 7 individuals. (B) Tonsillar subpopulations were sorted and FcRH1 mRNA levels were examined by real-time PCR and normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression. Mean levels (± SDs) are shown for each subpopulation in 3 tonsillar samples.