FIGURE 1.

Spectrum of antigen-specific T cell–EC interactions.(A) naïve T cells immunologically ignore resting ECs which express MHC class I, but are MHC II^low or MHC II^-. (B) Effector CD8⁺ T cells can recognize cognate antigen on ECs leading to EC activation and may potentially damage the vascular bed. (C) Activated ECs upregulate expression of MHC II, adhesion molecules and ligands of T cell co-inhibitory molecules. Engagement of co-inhibitory molecules can lead to tolerization of both CD8⁺ and CD4⁺ T cells and hence preserves the integrity of the EC layer. ICAM1, intercellular adhesion molecule 1; LFA1, leukocyte function-associated antigen 1; MHC I/II, major histocompatibility complex I/II; PD-1, programmed cell death 1; PD-L1, programmed cell death ligand 1; TCR, T cell receptor.