Proliferation of Cells in the Oral Mucosa, the Ear Skin and the Regional Lymph Nodes in Mice Sensitized and Elicited with a Hapten

During contact sensitivity reaction, immune cells proliferate. In order to study the histological picture of these proliferation phases, we used a mouse model of contact sensitivity in the oral mucosa and on skin. We also used bromodeoxyuridin (BrdU, an analogue to thymidin) that is incorporated into the nucleus during cell replication. The hapten oxazolone (OXA) was used to sensitize and elicit the oral mucosa and/or the ear skin. Mice were killed at various times after elicitation, and unsensitized animals were also exposed to the hapten as controls. BrdU (25 mg/kg animal) was injected i.p. 2 h before the kill. Specimens from the oral mucosa, ear skin and submandibular and auricular lymph nodes were cut and fixed in 4% paraformaldehyde. They were then treated with acid and biotinylated anti-BrdU antibody and developed using ABC-kit and DAB. The analyses were performed using a Leica light microscope and the computer program ANAlysis. In the oral mucosa, the frequency of proliferating cells were increasing during the observation period, 4–24 h after elicitation, regardless of site of sensitization. The proliferating cells were found mainly in the basal cell layer of the epithelium. Similar patterns were found in ear skin. The regional lymph nodes demonstrated a few scattered proliferating cells 4 h after elicitation. After 24 h, these cells were found frequently in the whole lymph node. Control animals exhibited considerable less proliferating cells at all times. We conclude that most proliferating cells were found 24 h after elicitation locally at the hapten-exposed sites (the oral mucosa or the ear skin) as well as in the regional lymph nodes.