Time course of appearance of CD and CTs. (A) αCDs, αGLT, αCTs, and AID transcripts were detected by PCR in CH12F3-2A cells at 0, 3, 6, 12, 24, and 48 h after stimulation. Similarly, the same set of molecules is detected in the cells prestimulated for 24 h at 0, 3, 6, 12, 24, and 48 h after removal of stimulation. For αCTs and αCDs, PCR products were transferred to nylon membrane and probed with internal oligonucleotides. The right bracket indicates range of αCD PCR products (1–10 kb) expected from recombination between Sμ (5 kb) and Sα (4 kb). The glyceraldehyde-3-phosphate dehydrogenase sequence and HPRT transcripts are amplified as an internal control for genomic PCR and RT-PCR, respectively. Lanes denoted with H2O indicate blank controls for cDNA. (B) Time courses of the increase in IgA+ cells after onset (right) or removal (left) of stimulation are shown.