ICAM and T-cell TEM. Endothelial ICAM-1 and ICAM-2 are required for TEM of T cells. (A) One representative experiment comparing TEM of the T-cell line SJLB.PLP3 across unstimulated and stimulated bEnd5 and ICAM-1-/-ICAM-2-/- bEndI1/2.1 is shown. Transmigration assays were performed with the use of 6.5-mm Costar transwells (Corning Costar, Bodenheim, Germany) with 5-μm pore size. T lymphocytes were collected for cell counting from the lower chamber and the bottom of the filter. Bars represent mean ± SD (n = 3). TEM of T cells across bEndI1/2.1 is reduced to an extremely low level (^***P < .001) when compared with bEnd5. This assay was reproduced 6 times. (B) One representative experiment is shown comparing transmigration of SJLB.PLP3 across bEndI1/2.1 deficient for ICAM-1 and ICAM-2; bEndI1/2.1-ICAM-1 (bEndI1/2.1 transduced with ICAM-1); bEndI1/2.1-ICAM-2 (bEndI1/2.1 transduced with ICAM-2); and bEndI1/2.1-ICAM-1/ICAM-2 (bEndI1/2.1 transduced with ICAM-1 plus ICAM-2). Re-expression of ICAM-1 or both ICAM-1 and ICAM-2 in bEndI1/2.1 reconstitutes TEM of PLP-specific T cells to extremely significant levels (^***P < .001), and re-expression of ICAM-2 reconstitutes TEM to very significant levels (^**P < .01) when compared with migration across bEndI1/2.1. This assay was reproduced 4 times. Bars represent mean ± SD (n = 3).