gamma delta cells involved in contact sensitivity preferentially rearrange the V gamma 3 region and require interleukin-7

Ptak and Askenase showed that both alpha beta and gamma delta cells are required for transfer of contact sensitivity (CS). This study confirms that day 4 immune cells depicted of gamma delta cells fail to transfer CS to trinitrochlorobenzene (TNP-Cl) systemically and demonstrates that administration of anti-gamma delta monoclonal antibodies (mAb) in vivo abolishes the CS reaction. Moreover, gamma delta cells accumulate at the antigen challenge site: these cells have the unusual phenotype CD8 alpha(+), CD8 beta(-), IL-4 R(+) which we suggest is due to their state of activation. Following immunization with contact sensitizer on the skin, the absolute number of gamma delta cells increases in the regional lymph nodes with a peak at 4 days. Of the gamma delta cells, 80%, both in the lymph nodes of TNP-Cl-immune mice and accumulating at the antigen challenge site are V gamma 3(+). The gamma delta cells expressing V gamma 3, which is characteristic of dendritic epithelial T cells (DETC), obtained 4 days after sensitization, proliferate in response to interleukin (IL)-7, but only poorly to IL-2 and IL-4. They also respond to concanavalin A and immobilized anti-gamma delta mAb, but not to haptens or heat-shocked syngeneic spleen cells. Furthermore, injection of mice with mAb to IL-7 inhibits accumulation of V gamma 3(+) cells both in the lymph nodes after skin sensitization and at the antigen-challenge site. Altogether, these results strongly support the view that DETC are related to, or the original source of, the gamma delta cells found in the lymph node after skin sensitization and at the site of challenge, and that IL-7 is implicated in these phenomena.