Immunohistochemistry using whole mount preparations of the murine mesentery revealed two types of LYVE-1-immunoreactive cells with dendritic morphology other than F4/80+ typical macrophages. The two types of LYVE-1+ cells were regularly distributed with constant intervals throughout the mesentery and appeared to possess their own territory. Both types of LYVE-1+ cells were weakly or moderately immunopositive for F4/80 antibody, a marker of macrophages, while F4/80+ round macrophages were absolutely free from the LYVE-1 immunoreactivity. Only macrophages could ingest latex particles of 20 nm in diameter 3 h after a peritoneal injection. Peritoneal administration of lipopolysaccharide (LPS) induced a rapid reduction of LYVE-1 immunoreactivity in the cells with dendritic morphology followed by an increased immunoreactivity to F4/80 antibody, and simultaneously by dynamic changes in their shape. Under normal conditions, F4/80+ macrophages in various connective tissues expressed LYVE-1, in contrast to lack of LYVE-1 in F4/80+ macrophages within the parenchyma of visceral organs and macrophages residing in hepatic sinusoids and pulmonary alveoli. LYVE-1 may play a role in cell adhesion and migration of macrophagic cells within connective tissues rich in hyaluronan, and loss of LYVE-1 becomes a reliable sign of activated conditions in inflammation.
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