Adhesion molecule LFA-1/ICAM-1 influences on LPS-induced megakaryocytic emperipolesis in the rat bone marrow.

Abstract

To investigate the effect of adhesion molecules on the occurrence of megakaryocytic emperipolesis of neutrophils, we examined the expression of lymphocyte function-associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1) in the bone marrow of lipopolysaccharide (LPS)-treated rats (experiment I) and the occurrence of megakaryocytic emperipolesis in anti-LFA-1 antibody-treated rats (experiment II). In experiment I, rats were injected with LPS intravenously at a daily dose of 0.5 mg/kg for 3 days. ICAM-1 was intensely stained on megakaryocytes in LPS treated rats, as detected by flow cytometric analysis. ICAM-1 was immunostained in the megakaryocytes showing emperipolesis. LFA-1 was immunostained in the neutrophils engulfed by megakaryocytes. In experiment II, rats received anti-LFA-1 antibody intravenously at a single dose of 3 mg/kg. One hour after treatment, rats were given LPS intravenously as a single dose of 0.5 mg/kg. The incidence of megakaryocytic emperipolesis was markedly lower in the anti-LFA-1 antibody + LPS group than in the LPS alone group. These findings suggest that the occurrence of megakaryocytic emperipolesis is partly dependent on adhesion molecules via LFA-1/ICAM-1.