Interaction between DC-SIGN expressed by macrophages and mannosylated surface immunoglobulin on the surface of FL cells. A diagrammatic view of a cell-cell interaction between a polarized macrophage expressing naturally tetrameric DC-SIGN and an FL cell carrying mannosylated motifs in the IGV region. Data in vitro show that DC-SIGN engagement leads to phosphorylation of intracellular kinases in FL cells.⁵⁴  BLNK, B-cell linker protein; BTK, Bruton tyrosine kinase; P, phosphorylation; PDK, phosphoinositide-dependent protein kinase; PI3K, phosphatidylinositol 3-kinase; PIP3, phosphatidylinositol (3,4,5)-tris- phosphate; PLC, phospholipase C.