Down-regulation of cell surface nucleolin on THP-1 monocyte-like cell surface after LVS infection. A: THP-1 cells in suspension were incubated first with anti-nucleolin either polyclonal (part A1) or MAb (part A2), diluted 1/200 and then treated with PFA. In part A3, THP-1 cells were first treated by PFA and then incubated with polyclonal anti-nucleolin Ab. Analysis was performed by fluorescence microscopy at 63× magnification. B: FACS analysis of nucleolin expression on cell surface of uninfected cells (B1) or cells infected for 30 min by LVS (B2). THP-1 cells were incubated either with anti-GAPDH as isotype negative control (dotted line) or with anti-nucleolin (solid line) MAbs. These experiments are representative of five different experiments.