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

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.