We recently found a novel GPI-anchored protein, GPI-80, on human phagocytes that may regulate leukocyte adherence, locomotion, and extravasation. To clarify the mechanisms by which GPI-80 functions on leukocytes, we explored the possibility of its physical association with beta2 integrin which is important for leukocyte adherence, locomotion, and extravasation. beta2 integrin, detected by anti-CD18 mAb, was coprecipitated with GPI-80 from human neutrophil lysates by a mAb to GPI-80. In addition, GPI-80 was immunoprecipitated from human neutrophil lysates by anti-human CD 18 mAb. These results clearly show that GPI-80 is physically associated with beta2 integrin in human neutrophils. (C) 2002 Elsevier Science (USA). All rights reserved.