EFFECTS OF A NEW IMMUNOSUPPRESSIVE AGENT, FK 506, ON THE EFFERENT LIMB OF THE IMMUNE-RESPONSES

The effects of a novel immunosuppressant, FK 506, on the efferent limb of the immune response were studied in the experimental autoimmune uveoretinitis (EAU) in the rat, using two different treatment schedules. First, rats actively immunized with S-antigen were treated with FK 506 only after the onset of EAU. FK 506 (1 or 3 mg kg-1 day-1) reduced the intensity of EAU as compared to that of non-treated rats. Especially, a daily dose of 3 mg kg-1 completely suppressed further development of EAU. It is, therefore, suggested that FK 506 treatment is effective in suppressing the ongoing process of the immune response, even after the disease has been initiated. Second, FK 506 (0·3 mg kg-1 day-1) was given only to the repicient rats which received IRBP-sensitized lymphocytes. None of FK 506-treated recipients developed EAU, while all control recipients developed the disease approximately 4 days after the cell transfer. The immune responses of FK 506-treated rats in the two experiments were also significantly suppressed. The antibody levels of S-antigen, the antigen-specific proliferative responses of lymphocytes, and even the proliferative responses to Con A were markedly suppressed in the rats in which FK 506 was given only during the efferent limb of the immune response. © 1990.