The sections were then colored by 3,3′-diaminobenzidine-tetrachloride as a substrate of peroxidase. Counter staining was performed by hematoxylin. Number and distribution of IgM positive cells were assessed using microscopy. Serum IgM data was expressed as mean ± standard error of the mean. Data between different groups were compared using the non-parametric Mann–Whitney U-test or Fisher’s exact test. All analyses were two-tailed P-values of less than 0.05 were considered statistically significant.

IMMUNOHISTOCHEMICALLY STAINED SERIAL sections of splenic tissues demonstrated that IgM positive cells were mainly distributed to the CD21 negative region nearby PALS (Fig. 1a,b) in positive cases. In PBC, IgM positive cells were accumulated in the CD21 positive lymph follicle in five PBC cases (63%) (Fig. 1c,d). CXCL13 positive FK506 cells were especially detected in the center of the lymph follicle where IgM positive cells accumulated in PBC (Fig. 1e). IgM positive BGJ398 clinical trial cells were not observed in chronic HCV infection (Fig. 1f). There was a statistical significance (P = 0.02) compared to PBC. In PBC cases which had IgM

positive cells observed in the spleen had relatively higher serum IgM (310.6 ± 119.9 vs 241.3 ± 39.6 mg/dL) but were not statistically significant (Table 1). As extrasplenic study, liver biopsy samples from PBC patients were stained for IgM and CXCL13 similarly. IgM positive cells surrounding the intrahepatic bile duct were observed

in one out of 10 cases of PBC. Interestingly, in IgM positive liver, CXCL13 was also positively stained at the bile duct (Fig. 2). SPLENIC WHITE PULP consists of PALS and lymph follicles and is surrounded by the marginal zone. CD21 staining is useful to identify the FDC network in lymph follicles for histopathological analysis of the spleen. Because accumulation of IgM positive cells was observed MCE公司 in the CD21 positive lymph follicle in splenic tissues collected from the PBC patients, it was suggested that IgM memory B cells proliferate and overproduce IgM in the spleen in PBC. We previously reported that Toll-like receptor (TLR)9 ligand CpG stimulates IgM memory B cells in the PBMC of PBC to produce an excessive amount of IgM.[3] It was also reported that TLR signaling stimulates generation of IgM memory B cells,[10] suggesting that circulating PAMP stimulate proliferation of the IgM memory B cells and IgM overproduction in the spleen. Such stimulation could be mediated by CD4 positive T cells[12] and CXCL13.[13] The present study demonstrated that the central region of the IgM positive follicle involves many CXCL13 positive cells in spleen in PBC. CXCL13 is a chemotactic chemokine that specifically stimulates B cells and is expressed in FDC, suggesting that FDC could essentially participate in IgM production in PBC.