Adherence reactions involving human leukocytes are mediated by a family of glycoprotein surface antigens composed of three different alpha subunits designated alpha L, alpha M, and alpha X, each of which is associated with a single beta subunit in an alpha 1 beta 1 heterodimer structure. We cloned the cDNA for the common beta subunit and investigated beta subunit mRNA expression in HL-60 promyelocytic leukemia cells and human granulocytic cells. Leukocyte adherence receptor beta subunit mRNA transcripts were present in low levels in HL-60 myeloblasts and promyelocytes and increased 10-fold or greater with chemically induced differentiation to more mature granulocytes (using retinoic acid and dimethylformamide) or monocyte/macrophages (using phorbol myristate acetate). Levels of beta subunit mRNA expression were also increased both in normal human peripheral blood granulocytes and in granulocytes from patients with chronic myelogenous leukemia. Nuclear run-off assays indicated that the increased steady state level of the beta subunit mRNA in retinoic acid-differentiated HL-60 cells was secondary to enhanced beta subunit gene transcription. We conclude that mRNA levels for the beta subunit of the receptor on human leukocytes that mediates cellular adherence are increased in more mature granulocytic cells compared to immature myeloid precursors and that this enhanced mRNA expression is transcriptionally regulated.
CD18 Antigens Cell Adhesion