CD147 expression and chemotactic activity. HeLa-CD4 cells stably transfected with anti-CD147 siRNA-expressing vector or empty vector control were sorted according to the level of CD147 expression into low, medium and high (cells transfected with empty vector) expressing clones (A). Chemotactic activity of the clones in response to CypA (B) or SDF-1α (C) was measured as described in Materials and Methods. Chemotactic activity was analyzed in triplicate and results are presented as mean ± SEM, *p < 0.05; **p < 0.01; ***p < 0.001. Results are shown for one representative experiment out of two performed.