Dynamic changes in epidermal Ia-positive cells in allergic contact sensitivity reactions in mice

Publisher Website
Google Scholar
Abstract
In mice sensitized with trinitrochlorobenzene, serial changes in epidermal Ia-positive cells were studied at various times after challenge. Until 3 days post-challenge, the Ia-positive cells consisted only of dendritic Langerhans cells; their number was decreased but they were significantly enlarged, with extending dendrites. Some Langerhans cells were also found surrounding a hair follicle, extending their dendrites toward the follicle like the spokes of a wheel. From 3-9 days after challenge, keratinocytes also began to express Ia antigens in the epidermis in addition to Langerhans cells, whose size diminished. There are 2 phases in the response of the epidermal Ia antigens in contact sensitivity reaction, i.e., an early phase in which enlarged Langerhans cells are the only Ia-positive cells in the epidermis, and a late phase in which keratinocytes take over as the major Ia-positive cells, while Langerhans cells resume their original size. Ia antigen expression on keratinocytes in this late phase probably plays a crucial role in completely eliminating allergens deposited on the keratinocytes.