FIGURE 1.

Distribution of endogenous CD36 following antibody and oxLDL cross-linking. A–C, distribution of CD36 on permeabilized resting RAW 264.7 cells (A), U937 cells (B), or human primary macrophages (C). D–F, cross-linking antibodies at 0 °C did not alter distribution of CD36 on RAW cells (D), U937 cells (E), or primary human macrophages (F). G–I, warming of cross-linked cells to 37 °C resulted in internalization of CD36. G, cross-linking in murine RAW cells involved an IgA primary antibody or a F(ab′)₂ fragment (inset). H and I, cross-linking of human U937 cells or primary macrophages involved IgG (clone 131.2) or IgM antibodies (insets). J, oxLDL also triggered CD36 internalization in RAW cells. K and L, CD36 is the major receptor for oxLDL. Wild-type mouse peritoneal macrophages (K) or CD36^−/− knock-out mouse peritoneal macrophages (L) were incubated with DiI-labeled oxidized LDL, and noninternalized oxLDL was removed by acid wash. Because the cells in L bind little oxLDL and are not readily visible by fluorescence microscopy, they are outlined in the main panels and shown by differential interference contrast image in the top inset. The lower inset shows quantitation of oxLDL uptake in murine wild-type (+/+) and CD36-deficient (−/−) macrophages, quantified from experiments like K and L. Data are means of three experiments, each counting at least 50 cells of each type. To facilitate comparison between experiments, data were normalized to wild type. In images A–I, the x-z plane is shown below. Scale bars, 10 μm.