FIG. 3.

In vitro class switch recombination occurs normally in ERK2-deficient B cells. Splenic B cells were purified and stimulated with 2 μg/ml of anti-CD40 MAb plus 10 ng/ml of mouse IL-4 for 4 days. (A) Total RNA was extracted, and γ1 germ line transcript (γ1GLT), γ1 postswitch transcript (γ1PST), AID (Aicda), and G3PDH (G3pdh) were detected by semiquantitative RT-PCR from threefold dilutions of each cDNA. (B) Genomic DNA was extracted and analyzed by DC-PCR. (C) CFSE-labeled B cells were stimulated and analyzed by flow cytometry to detect the progression of cell division and IgG1-bearing B cells concurrently. All results are representative of at least two independent experiments.