Staphylococcal infection and the limbus: study of the cell-mediated immune response

The relationship between enhanced cell-mediated immunity (CMI) to staphylococcal antigens, expressed as delayed hypersensitivity (DH), and the development of catarrhal infiltrates at the limbus in the rabbit has been explored by others. This DH is required for infiltrates to develop in the rabbit cornea when it is exposed to conjunctival inoculation with live Staphylococcus aureus cells. Similar investigations have not been pursued in the human, although St. aureus has been isolated from lids of patients with sterile marginal ulcers. We have tested 69 patients with blepharitis, eleven with and 58 without associated symptomatic marginal keratitis, for DH to killed whole cells of St. aureus and St. epidermidis and protein A; quantitative cultures have also been collected from lids and conjunctivae. Preliminary findings show that nine out of 11 patients with symptomatic marginal keratitis, requiring treatment with steroids, have enhanced DH to St. aureus cell wall antigens. We suggest the hypothesis that this type of marginal keratitis in the human is the result of enhanced CMI at the limbus to St. aureus cell wall antigens.