CIITA interacts with Tax-2 in vivo. 293T cells were transiently co-transfected with either one of the following CIITA plasmids pcfCIITA wt (3 μg), pcfCIITA 1-252 (3 μg), pcfCIITA 253-1130 (3 μg), pcfCIITA 253-410 (3 μg), pcfCIITA 1-321(1.5 μg) and pTax-2 V5 (2 μg) vector. Extracts were immunoprecipitated (IP) with the anti-V5 monoclonal antibody and the purified complexes were immunoblotted (WB) with the anti-Flag antibody for the detection of CIITA and its deletion fragments (top panels). The expression of the proteins in all cell extracts was also examined by WB (input) with the anti-Flag antibody. TFIIB was used as a control to show that equal amounts of total protein were loaded in each lane (bottom panels). To be noted, the input expression of the CIITA fragment 1-252 was evaluated in a different western blot gel as underlined by the lines in lane 2. IgH, non specific band representing the immunoglobulin heavy chain of the anti-V5 antibody recognized in western blots after immunoprecipitation and detection with HRP-conjugated anti-rabbit or anti-mouse Ig secondary antibody.