PRDM1 and viral infectious disease: Conversely, loss of TCF-1 promoted the expression of Th1 cell-associated factors in Tfh cells, including T-bet, Blimp-1, and CD25 protein.75,76 Finally, dually expressed p33 (an isoform of TCF-1) and Bcl6 proteins physically interact and act to recover Bcl6-mediated autorepression.76 However, whether Bcl6 forms a heterodimer with p33 or Bcl6-p33 recruits another transcriptional regulator to reverse Bcl6 autoregulation in the context of viral infection remains unclear.