For Western blots 3 × 106 B cells were lysed in RIPA buffer. Nitrocellulose membranes were blocked in Tris-buffered saline/5% dry milk, and incubated with anti-RAG-1 1 : 200, anti-Ku70 1 : 1000, Fluorouracil anti-RAG-2 1 : 200, anti-GAPDH (Millipore, Schwalbach, Germany) or anti-β-actin (Cell Signaling Technologies, Danvers, MA). Real-time RT-PCR was performed using a High Pure RNA Isolation Kit (Roche), First Strand cDNA Kit with oligo(dT) primers (Fermentas, St Leon-Rot, Germany), Absolute QPCR SYBR GREEN Low ROX Mix (ABgene House, Epsom, UK), primers

(Table 1, MWG Biotech) and a 7900 HT Fast Real Time PCR System (Applied Biosystems, Darmstadt, Germany). Relative expression to β-actin was calculated as rE = 1/(2Ct(target) − Ct(β-actin)). Interleukin-6 (72 hr) was EGFR inhibitors cancer measured using the OptEIA ELISA kit (BD Biosciences); IgM (13 days) was quantified using the IgM ELISA (Bethyl Laboratories, Montgomery, AL). For polyreactivity ELISA, plates were coated with 10 μg/ml lipopolysaccharide (Sigma), pneumovax (Aventis Pasteur, Lyon, France), tetanus toxoid (Statens Serum Institute, Copenhagen, Denmark) or 100 μg/ml salmon

sperm DNA [Sigma; double-stranded DNA (untreated), single-stranded DNA (boiled)], rehydrated, blocked with PBS/3% FCS and incubated with B-cell supernatant and anti-human immunoglobulin-horseradish peroxidase (1 : 5000). Statistical significance was determined using the paired two-tailed Student’s t-test; significant differences are indicated with *P ≤ 0·05 and **P ≤ 0·005. In the present study we asked whether TLR9 could participate in receptor revision. As IL-6

was previously found to be essential for the expression of RAG proteins in B-cell progenitors[20] and in mature B cells,[5, 6] we first determined the preconditions for induction of B-cell-derived IL-6: CpGPTO represented potent inducers of IL-6 (Fig. 1a), but IL-6 was also stimulated by combination of CD40L and rhIL-4, used as a surrogate for T-cell help (Fig. 1a), and combination of CpGPTO with Staurosporine chemical structure CD40L synergistically enhanced IL-6 production (Fig. 1a). By comparison, CpGPTO triggered proliferation in all conditions but the combination of CD40L and rhIL-4 (Fig. 1b). Having confirmed this prerequisite for re-expression of RAG, we approached the analysis of RAG expression. RNA and protein lysates from freshly isolated peripheral blood B cells were compared with those from B cells stimulated with CpGPTO, CD40L ± rhIL-4 or a combination of these stimuli. As expected, RAG-1 mRNA was not found in freshly isolated B cells but – paralleling IL-6 induction – became detectable in B cells stimulated for 24 hr or longer with either CD40L/rhIL-4 or CpGPTO, or combinations of CpGPTO with CD40L ± rhIL-4 ± BCR stimulation with anti-human immunoglobulin F(ab′)2 (Fig. 2a).