Effect of kinase inhibitors on the secretion of CCL5, CXCL8 and IL-6 by PMA-differentiated U937 macrophages stimulated with the recombinant SspA (33 μg/ml) of S. suis. A value of 100% was assigned to the amounts of cytokines detected in the absence of kinase inhibitors. The data are the means ± SD of triplicate assays from three separate experiments. Asterisks indicate a significant difference in comparison with the control (no inhibitor) at P < 0.01. The JNK inhibitor is specific for c-JUN N-terminal kinase (JNK) inhibitor, U0126 is specific for mitogen-activated extracellular kinase 1, 2 (MEK 1, 2) inhibitor, and SB203580 is specific for p38 mitogen-activated kinase (p38 MAPK) inhibitor.