Characterization of the Myeloid - Specific C D l l b Promoter

The C D l l b/CD18 heterodimeric surface antigen is expressed exclusively on human monocytes, macrophages, granulocytes, and natural killer cells. During differentiation of myeloid cell lines, CDl lb steady state messenger RNA levels increase significantly; we show here that CDl lb transcription rates increase commensurately. A 1.7-kb fragment of C D l l b 5’ flanking sequence directs expression of a reporter gene specifically in myeloid cell lines. Deletion analysis localizes elements directing high levels of tissue-specific