Figure 1.

Differential endocytosis of albumin nanoparticles by PMN. (A) Flow cytometric analysis of mouse lung single cell suspensions. Intravenous injection of albumin nanoparticles (ANP) led to endocytosis of ANP by CD177⁺Ly6G⁺ lung PMN. (B) Transmission electron microscopy (TEM) of lung neutrophil that did not endocytose ANP (ANP^low) and of lung neutrophil that endocytosed ANP (ANP^high). Red arrows indicate ANP in organelles. (C) Flow cytometric analysis of ANP endocytosis by mouse Ly6G⁺ PMN from various tissues. ANP^high PMN were found in bone marrow, peripheral blood, spleen, and lungs at low percentage when compared to PMN that did not endocytose ANP (ANP^low). Systemic challenge (i.v.) with LPS induced the expansion of ANP^high PMN relative to ANP^low PMN, which was most pronounced in lungs (ratio of 9.78). Mice (n = 4 per cohort) were injected with LPS 6 h prior to euthanasia and with unlabeled ANP (control) 30 min prior to euthanasia; with LPS or saline 6 h prior to euthanasia and with AF647-fluorochrome labeled ANP 30 min prior to euthanasia.