ICAM1 and infection: Thus, during infection, the main vascular ligand expressed by the vast majority of peribronchial vessels is VCAM-1, while the main vascular ligand expressed by all pulmonary capillaries is ICAM-1 with constitutive expression of the low affinity LFA-1 ligand ICAM-2 shared by both capillary and peribronchial blood vessels (22).