FIG. 1.

Inducible expression of IL-4 and IL-5 by RBL-2H3 cells. (a) Cells were exposed to no stimulus (lane 1), antigen (lane 2), or PMA-A23187 (lane 3) for 4 h, and RNA was then extracted. RT-PCR was performed, and products were detected by electrophoresis and Southern hybridization. The control RNA, β-actin RNA, was readily detected in all samples, attesting to the integrity of the RNA. Negative controls were omission of reverse transcriptase enzyme from the RT (lane 4, which was otherwise identical to lane 3) and omission of cDNA from the PCR (lane 5). (b) Cells were exposed to no stimulus (lane 6), PMA (lane 7), A23187 (lane 8), or PMA-A23187 (lane 9), and mRNA was detected as described above. Percent β-hexosaminidase releases in this experiment were as follows: no stimulus, 0.5%; PMA stimulus, 2.4%; A23187 stimulus, 43.8%; PMA-A23187 stimulus, 36.7%.