Activation of CD74 expressed on primary B cells controls TAp63 transcription. (A) Primary B cells were transfected for 8 hours with various constructs of CD74 using AMAXA reagents, as described in “Cell transfection.” Transfection efficiency was determined by analyzing the mRNA levels of a sequence that is shared in all CD74 constructs. RNA was isolated and TAp63 transcription was determined by RT-PCR. (B) Control IgD⁺ or CD74^−/− B cells were incubated in the presence or absence of anti-CD74 antibody or control anti-CD8 antibody for 24 hours. Total RNA was isolated and RT-PCR was performed, as described in “RNA isolation and reverse transciption.” The results presented are representative of 3 different experiments. (C) Control IgD⁺ cells were incubated in the presence or absence of anti-CD74 antibody, for various lengths of time. Total RNA was isolated and RT-PCR was performed, as described in “RNA isolation and reverse transciption.” The results presented are representative of 3 different experiments. (D) Primary B cells were incubated with MIF 100 μg/mL for various lengths of time. Total RNA was isolated and RT-PCR was performed, as described in “RNA isolation and reverse transcription.” The results presented are representative of 3 different experiments. The intensity of the p63 band was calculated as described in Figure 2.