Taken together, it is possible that the interaction of CCR4, CCR9, and possibly CD103 and CD108 with their ligands secreted or expressed on activated endothelial cells and conjunctiva favours the selective adhesion of a circulating CD4+ T cell subset with an activated phenotype and the ability to respond to antigens, driving the immune-response to the ocular mucosa and inducing a proinflammatory microenvironment related to Th2 perennial allergic conjunctivitis. Here, CD4 is linked to atopic conjunctivitis.