Genomic CIITA-PIII DNA from leukemic T cells is methylated. (A) Restriction sites around CIITA-PIII of the methylation-sensitive enzyme HpaII and its methylation-tolerant isoschizomer MspI are indicated with vertical arrows. The probe used for the Southern blot analysis is indicated as a gray box. Detected fragment sizes are indicated. (B) Southern blot analysis on HindIII/HpaII (H) and HindIII/MspI (M) digested DNA of CIITA-deficient or CIITA-expressing T-cell lines. JEG-3 DNA was used as a control for methylated CIITA-PIII,39 and Raji B-cell DNA was used as a control for unmethylated CIITA-PIII. (C) The methylation status of CIITA-PIII in primary T-cell leukemia and lymphoma as determined by Southern blot analysis on HindIII/HpaII (H) and HindIII/MspI (M) digested DNA. The HLA-DR surface expression of the panel of primary malignant T cells has been determined previously (Table 1; Van Dongen et al31 and Langerak et al32,33 ).
