PURPOSE. The ocular surface epithelium is part of the mucosal defense system. Because transcription factor NFB in mucosal epithelial cells plays a central role in regulating the genes that govern the onset of mucosal inflammatory responses, we examined the role of a regulator of NFB, I B , in murine ocular surface inflammation. METHODS. The eyes of I B / mice were analyzed biomicroscopically and histologically. I B expression in normal mouse cornea and conjunctiva was examined by RT-PCR. The results were compared with those obtained in other tissues by realtime PCR. I B mRNA on the ocular surface and in other mucosal tissues was localized by in situ hybridization. RESULTS. I B / mice manifested chronic inflammation, specifically in the ocular surface, but not in other tissues. In normal mice, I B was expressed in a variety of mucosal tissues. The I B transcript was predominantly distributed in the epithelia of these tissues. As inflammatory symptoms progressed on the ocular surface of I B / mice, inflammatory cells, mainly CD45R/B220 and CD4 cells, intensely infiltrated the submucosa of the conjunctival epithelia. This infiltration was accompanied by an almost complete loss of goblet cells in the conjunctival epithelia.