Fig. 1. Embryonic macrophages and larval hemocytes in primary culture bind and internalize Cy3mBSA via endogenous scavenger receptors. Embryonic macrophages (A, arrows) and larval hemocytes (C, arrows) in culture are the only population of cells from wild-type animals to internalize Cy3mBSA. The fluorescence image of cells (outlined in A and C) indicates that Cy3mBSA uptake is specifically mediated by ALBR endogenously expressed in embryonic macrophages (B) and larval hemocytes (D). Inset in panel D shows that binding and uptake of Cy3mBSA (D, arrows) can be competed by excess unlabeled mBSA. Histogram in panel E shows the relative amount of Cy3mBSA internalized via ALBR in hemocytes incubated in the absence (Control) or presence of excess unlabeled mBSA, fucoidan or LPS, expressed as a fraction of total endocytosed Cy3mBSA internalized in the absence of any other competing ligand. Bar, 5 µm.