FR252921, a novel immunosuppressive agent isolated from Pseudomonas fluorescens no. 408813 III. In vivo activities.

A novel immunosuppressive agent, FR252921 was isolated from the cultured broth of a species of Pseudomonas fluorescens. We have shown that FR252921 inhibit activating protein-1 (AP-1) transcription activity and act dominantly against antigen presenting cells comparing to T cell. Possibility of FR252921 as concomitant drug of FK506, T-cell specific inhibitor was evaluated. FR252921 showed synergy with FK506 in immunosuppressive activity both in splenic proliferation and in murine skin transplantation.