Figure 3: Expression of IL-4 mRNA in BB spleen cells transduced with MSCVneo or MSCVneo.IL-4 retroviral vectors, as outlined. BB spleen cells were activated for 48 h with Con A in the presence of rIL-2, harvested and subsequently incubated in the presence of MSCVneo.IL-4-containing supernatants, as described in Materials and Methods. Total RNA was extracted from transduced cells and the presence IL-4 mRNA was examined by RT-PCR. β-Actin was used as a positive control. PCR products were visualized on 2% agarose gels with ethidium bromide.