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 ar e required for transfer of contact sensitivity (CS). This study confir ms that day 4 immune cells depicted of gamma delta cells fail to trans fer CS to trinitrochlorobenzene (TNP-Cl) systemically and demonstrates that administration of anti-gamma delta monoclonal antibodies (mAb) i n vivo abolishes the CS reaction. Moreover, gamma delta cells accumula te at the antigen challenge site: these cells have the unusual phenoty pe CD8 alpha(+), CD8 beta(-), IL-4 R(+) which we suggest is due to the ir state of activation. Following immunization with contact sensitizer on the skin, the absolute number of gamma delta cells increases in th e 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 re sponse to interleukin (IL)-7, but only poorly to IL-2 and IL-4. They a lso respond to concanavalin A and immobilized anti-gamma delta mAb, bu t 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 a ntigen-challenge site. Altogether, these results strongly support the view that DETC are related to, or the original source of, the gamma de lta cells found in the lymph node after skin sensitization and at the site of challenge, and that IL-7 is implicated in these phenomena.