HLA-E mRNA and protein expression in cultured human ECs. (A) Quantification and comparative analysis of mRNA steady state levels for HLA-A, HLA-B, and HLA-E in cultured ECs by competitive RT-PCR. Values are mean ± SD (n = 3). *P < .01 versus HLA-B. (B) Regulation of HLA-E mRNA in response to TNFα or IFNγ was assessed by semiquantitative RT-PCR. PCR amplifications for β-actin were used as controls. RNA 18S and 28S are shown below. (C) Confocal microscope images showing comparative cell-surface staining for HLA-A, HLA-B, HLA-C (i, ii) and HLA-E (ii, iv) on nonpermeabilized (i-ii) and permeabilized (iii-iv) vascular ECs. Nuclei were stained with To-pro-3 (red). (D) The colocalization of HLA-E (left panel; green) rhodamine-B-hexyl ester (for ER staining) or anti–golgin-97 (for Golgi staining, both middle panel; red) on permeabilized ECs. Merged images are shown on the right panel. Colocalization is shown in yellow. Original magnification, ×63. Scale bar equals 15 μm (applies to all figures).