Induction and suppression of contact sensitivity to fluorescein isothiocyanate (FITC).

Although both fluorescein isothiocyanate (FITC) and trinitrophenyl (TNP) covalently couple primarily to the epsilon-amino group of lysine residues of surface glycoprotein, FITC is structurally different from TNP. In this paper, we investigated the immune regulatory mechanisms in contact sensitivity (CS) to FITC by the administration of FITC and FITC-conjugated epidermal cells (FITC-EC) via various routes. Mice injected with FITC via i.p. or i.v. route did not induce CS but induced hyporesponsiveness to the following sensitization with FITC painting. Mice injected with FITC via s.c. route induced neither CS nor hyporesponsiveness to the following FITC painting. Administration of FITC via i.v. route was demonstrated to induce hapten-specific suppressor T cells. Inoculation of FITC-EC via s.c. or i.p. route induced CS, whereas injection of FITC-EC via i.v. route did not induce CS but induced hyporesponsiveness to the following FITC painting. The results are compared with the previous data obtained by trinitrobenzene sulfonate and trinitrophenyl-conjugated epidermal cells.