Surface interleukin-6 receptors were identified on human polymorphonuclear leukocytes (PMNL) by monoclonal anti p80-chain antibody MT 18 Cytoplasmic RNA harvested from PMNL also contained IL-6-R transcripts. Binding of recombinant human (rh) interleukin-6 (IL-6) to IL-6-R bearing PMNL was identified by flow cytometry using phycoerythrin (PE)-conjugated ligand. Treatment of PMNL with rh granulocyte-macrophage colony-stimulating factor (GM-CSF) led to the inability of PMNL to bind MT 18 monoclonal antibody (moAb) and to display binding sites for PE-conjugated rh IL-6. Levels of IL-6-R transcripts in PMNL exposed to GM-CSF were about 5-fold below those of PMNL cultured in medium only. Though a definitive role for IL-6 to modulate the function of PMNL was not found, treatment of PMNL with rh IL-6 clearly resulted in an enhancement of transcript levels of the early response genes c-fos and c-jun in these cells, thus indicating that IL-6 binding is followed by signal transduction.