Cyclosporin A inhibits the delayed-type hypersensitivity reaction: impaired production of early pro-inflammatory mediator(s).

The effect of cyclosporin A (CsA) on the delayed-type hypersensitivity (DTH) elicited in mice by sheep red blood cells was investigated. Evidence is presented that a single injection of CsA adversely affects the inflammatory reaction. Sensitized T lymphocytes initiate the DTH reaction by their recruiting activity on phagocytic cells which infiltrate the cutaneous site of antigen deposition. CsA administration has no adverse effect on the recruitment of phagocytic cells at the site of the inflammatory reaction. The present studies show that CsA acts on specific T cells: (a) in adoptive transfer, T-DTH-mediating cells cannot elicit a response in mice treated with CsA 8 h before; (b) when collected 8 h after a single injection of CsA, T-DTH-mediating lymphocytes are no longer able to adoptively transfer the reaction. This conclusion is strengthened by in vitro studies: (a) the frequency of T-DTH-mediating lymphocytes is 50-fold decreased after a short in vitro incubation with CsA; (b) in vitro production by concanavalin A-activated lymphocytes of chemotactic pro-inflammatory mediator(s) is abolished in presence of CsA.