PHAGOCYTOSIS OF APOPTOTIC BODIES BY LIVER ENDOTHELIAL-CELLS

Using electron microscopy and cytofluorimetry we studied the role of c arbohydrate-specific recognition systems in the interaction of apoptot ic bodies with normal and interleukin 1-activated sinusoidal endotheli al cells, Microfluorimetric observation of liver tissue sections revea led octadecyl-rhodamine B-labelled apoptotic body binding to the sinus oidal wall of mouse liver, when they were injected intraportally. Plat e-scanning cytofluorimetry demonstrated that about 20-25% of Acridine Orange-labelled apoptotic bodies could adhere specifically to cultured endothelial cells after 15 minutes of incubation, Adhesion increased to 30% when the cells were incubated for 60 minutes, Using a mixture o f galactose/N-acetylglucosamine/mannose as competition solution apopto tic body adhesion was significantly reduced especially after longer ti mes of incubation, when the percentage of inhibition reached 50%. Foll owing 4 hours exposure of liver endothelial cells to 1 ng/ml human rec ombinant interleukin-1 beta adhesion markedly increased after 60 minut es of incubation, whereas the co-incubation of interleukin-1 beta with the inhibitors brings down the adhesion to basal values obtained in c ontrols, Electron microscopic observation of the adhesion process show ed that the number of endothelial cells binding apoptotic bodies gradu ally increased from low to high values with time. After 60 minutes of incubation, the majority of apoptotic bodies were seen inside phagosom es and only a few remained at the cell surface, Liver endothelial cell s bound and endocytosed apoptotic bodies through carbohydrate-specific receptors, Moreover, this scavenger action was interleukin-1 enhanced , thus suggesting its possible activation during inflammatory and immu ne processes.