Lack of CIITA expression after stimulation in T-ALL cell lines. T-cell lines were unstimulated or stimulated with 10 ng/mL PMA and 1 μg/mL ionomycin in the medium for 4 days. RT-PCR analysis was then performed with primers specific for CIITA-PIII, IFNγ, or IL-4. GAPDH was used as control for equal cDNA loading. H₂O indicates water control; CD4⁺, CD4⁺ peripheral human T cells activated with 10 ng/mL PMA and 1 μg/mL ionomycin for 4 days.