The level of expression of CD11b and HLA-DR surface molecules on monocyte-like THP-1 cells increased significantly as a result of transmigration of these cells through a monolayer of endothelial cells. The expression of all studied markers (CD11b, HLA-DR, and CD-14) increased significantly after transendothelial migration in the presence of TNF-alpha and IFN-gamma. The changes in surface phenotype of THP-1 cells after transendothelial migration in the presence of TNF-alpha were more pronounced than in the presence of IFN-gamma. Transendothelial migration of THP-1 cells in the presence of IL-4 caused less pronounced changes in the surface phenotype, which did not differ from changes in transmigration without cytokines.