Klf3, Klf5, and Klf6 mRNA expression in lymphoid cells. Total RNA from p5424 pro-T, EL-4 mature T, A20 B-cell lines, and primary mouse tissues, including wild-type and RAG-2–deficient thymus, spleen, bone marrow, and intestine, were serially diluted (1:5:25:125) and amplified by RT-PCR using specific primer pairs under optimal conditions with β-actin as a control.