PR domain zinc finger protein 1, or B lymphocyte-induced maturation protein-1 (BLIMP-1), is a protein in humans encoded by the gene PRDM1 located on chromosome 6q21. BLIMP-1 is expressed in both B and T cells and plays a significant role in B cell development and antibody production. In B cells, it is a regulator of plasma cell differentiation. In T cells, it is crucial for most terminal effector cell differentiation in CD 4 and CD8 T cells. BLIMP-1 acts as a repressor of beta-interferon (β-IFN) gene expression. The protein binds specifically to the PRDI of the β-IFN gene promoter. Transcription of this gene increases upon virus induction.