ANTIGEN PRESENTATION IN THE MURINE ORAL EPITHELIUM

We have previously reported that the buccal mucosa can support delayed type hypersensitivity (DTH) reactions to contact sensitizers. In the present study, we show that cells isolated from the buccal epithelium are able to present soluble exogenous antigens to specific T cells. Si ngle cell suspensions obtained by enzymatic dispersion of buccal epith elial sheets could present the native protein antigen hen-egg lysozyme (HEL) to the I-A(k)-restricted CD4(+) T-cell hybridoma specific for a .a 46-61 on HEL. T-cell activation resulted in interleukin-2 (IL-2) pr oduction which could be inhibited by anti-major histocompatibility com plex (MHC) class-II antibodies of pertinent specificity. Immunohistoch emical staining of whole buccal epithelial sheets revealed that all MH C II positive cells had a dendritic morphology and expressed ATPase ac tivity, indicating that these cells represent a major antigen-presenti ng cell (APC) population in this tissue. Furthermore, single cell susp ensions isolated from buccal epithelium (BEG) after local in vivo admi nistration of either a native soluble protein, a synthetic dodecapepti de, or a contact sensitizer were able to activate antigen-specific T c ells ex vivo. Kinetic analyses indicated that maximal APC activity in the oral epithelium occurred within 1 hr after local antigen administr ation, and had essentially vanished after 24 hr. Conversely, APC activ ity was undetectable in draining cervico-mandibular lymph node cell su spensions recovered 1 hr after local antigen injection but became mani fest after 3-24 hr. These observations suggest that dendritic cells ca n acquire antigens in the buccal epithelium and migrate to draining ly mph nodes where they present processed antigen to MHC class II-restric ted T cells. This APC population may thus be a critical element in the initiation of Th1-driven DTH responses in-the oral mucosa.