CCAAT/enhancer-binding protein delta is a bZIP transcription factor which can bind as a homodimer to certain DNA regulatory regions. It can also form heterodimers with the related protein CEBP-alpha. The protein is important in the regulation of genes involved in immune and inflammatory responses, and may be involved in the regulation of genes associated with activation and/or differentiation of macrophages. CEBPD is involved in regulation of apoptosis and cell proliferation. It probably acts as tumor suppressor. One study in mice showed that CEBPD prevents development of tubular injury and tubulointerstitial fibrogenesis during the progression of chronic obstructive nephropathy.