Regulation of expression of the CD11b and CD18 subunits of the neutrophil adherence receptor during human myeloid differentiation.

The receptor on human myeloid cells that mediates cellular adherence consists of a heterodimer complex (designated CD11b/CD18). This receptor complex plays a critical role in leukocyte chemotaxis, adherence to vascular endothelium, and phagocytosis. We investigated expression of the CD11b subunit of this adherence receptor complex in various leukocyte populations. As previously described for the CD18 subunit, enhanced CD11b surface antigen and mRNA expression are present in peripheral blood granulocytes, as well as in chemically induced, differentiating HL-60 cells. However, in contrast to CD18 mRNA expression, which is transcriptionally regulated in differentiating HL-60 cells, the steady state levels of CD11b mRNA appear to be post-transcriptionally regulated in these cells. Thus, although the steady state levels of mRNA for the individual subunits of the CD11b/CD18 adherence receptor complex generally parallel each other during human myeloid differentiation, the mechanisms responsible for regulating these levels are distinctly different.