Detection of mRNA production by RT-PCR in cytokine-treated BALB/c mice (groups 1 to 6). At day 21 after BCL1 inoculation and cytokine treatments, splenic T cells were isolated and their RNA extracted for analysis. They were probed for the presence of IL-4, IL-10, and IFN-γ messages in RT-PCR. A plasmid containing the cDNA for all three cytokines served as the positive control (PC). Negative control (NC) lanes were without template DNA.