B-in expansion in Ipsilateral PLN and ILN of TNF-Tg mice with inflammatory arthritis. PLN and ILN (n ≥ 4) were harvested from wild-type (WT) mice, one- to two-month old TNF-Tg mice before the onset of ankle arthritis and PLN expansion (Pre Exp), and older TNF-Tg mice with established disease after PLN expansion (Exp), or after PLN collapse (Col), and used for multicolor flow cytometry as described in Materials and methods. The B-in population was quantified from the B220+/IgM+ fraction based on CD21 and CD23 staining, as illustrated by representative histograms of ipsilateral PLN (A), and ILN (B), from each group. This gating approach segregates the phenotypic follicular B cells (Fo), the marginal zone B cells (MZ), and the B-in population. The percentage of each population is shown. The percentage of B-in cells within this B220+/IgM+ fraction from PLN (C), and ILN (D); and the absolute number of B-in cells from PLN (E) and ILN (F) are presented as the mean +/- SD for each group (*P < 0.05, **P < 0.01, ***P < 0.001).