Induction of ICAM-1 expression on the eosinophilic leukemia cell line-3 (EoL-3) by platelet-activating factor and platelet factor 4

Background: Eosinophils are assumed to transmigrate to local tissue under the direction of the eosinophil chemotactic factor present in allergic inflammatory lesions. Objective: We examined whether PAF and PF4, which are related to eosinophil localization, affect the expression of ICAM-1 on the human eosinophilic leukemia cell line (EoL-3). Methods: ICAM-1 expression on EoL-3 cells in the presence or absence of PAF or PF4 was assessed by immunofluorescent analysis. The presence of sICAM-1 in culture supernatants of EoL-3 cells was detected with an ELISA kit. Results: Both PAF and PF4 enhanced the expression of ICAM-1 on EoL-3 cells. We found no difference in sICAM-1 concentration with or without PAF or PF4. Conclusions: The eosinophil chemotactic factors PAF and PF4 not only may attract eosinophils, but they may enhance the expression of ICAM-1 on eosinophils at the site of the lesion. Further, it is suggested that the shedding of ICAM-1 has little relation to the induction of ICAM-1 expression in vitro