1. T. S. Griffith and S. M. Fletcher, Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
2. T. Brunner and D. R. Green, Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
3. T. A. Ferguson, Departments of Ophthalmology and Visual Sciences and Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.