Expression of CR3 is not affected by HB-19. A. FACS analysis of CR3 expression on surface of THP-1 cells preincubated with 10 μM HB-19 (A1) or 10 μM 9R (A2). THP-1 cells were incubated either with anti-GAPDH as negative control (dotted line) or with anti-CR3 (solid line) MAbs. These experiments are representative of three different experiments. B. Binding of E-C3bi on THP-1 cells preincubated either with RPMI, 10 μM HB-19, 10 μM 9R or 20 μg anti-CR3 was determined by counting 100–200 cells by phase-contrast microscopy. Data show mean from three independent experiments ± SD values indicated as error bars.