γδ cells involved in contact sensitivity preferentially rearrange the Vγ3 region and require interleukin‐7

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Abstract
Ptak and Askenase showed that both αβ and γδ cells are required for transfer of contact sensitivity (CS). This study confirms that day 4 immune cells depleted of γδ cells fail to transfer CS to trinitrochlorobenzene (TNP‐Cl) systemically and demonstrates that administration of anti‐γδ monoclonal antibodies (mAb) in vivo abolishes the CS reaction. Moreover, γδ cells accumulate at the antigen challenge site: these cells have the unusual phenotype CD8α+, CD8β‐, 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 γδ cells increases in the regional lymph nodes with a peak at 4 days. Of the γδ cells, 80%, both in the lymph nodes of TNP‐Cl‐immune mice and accumulating at the antigen challenge site are Vγ3+. The γδ cells expressing Vγ3, 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‐γδ mAb, but not to haptens or heat‐shocked syngeneic spleen cells. Furthermore, injection of mice with mAb to IL‐7 inhibits accumulation of Vγ3+ 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 γδ cells found in the lymph node after skin sensitization and at the site of challenge, and that IL‐7 is implicated in these phenomena.