Use of lysine derivatives (I), or their acceptable salts for treatment and/or prevention of inflammatory diseases. Use of lysine derivatives of formula (I), or their acceptable salts, for treatment and/or prevention of inflammatory diseases. X : hydroxy, amino, alkoxy, Pro or Pro-Thr (I) may be N-acylated and/or C-amidated or -esterified. An independent claim is also included for in vitro preparation of cells that can impart tolerance to an antigen (Ag) by treating antigen-presenting cells (APC) with alpha-melanocyte stimulating hormone (aMSH), or its biologically active fragments or derivatives, and with Ag, in either order or simultaneously. [Image] ACTIVITY : Antiinflammatory; Antiallergic; Immunosuppressive; Antifibrotic; Dermatological; Antipsoriatic; Antiasthmatic; Antiulcer. Mice were sensitized to the hapten DNFB, then (after 7 days) the same hapten was applied to the ear, and after a further 24 hr the swelling of the ear was measured. The mean value was 7 (mmX10 -2>), but only 1 when the mice had been injected, intraperitoneally, with an unspecified dose of Lys-Pro-Thr, 2 hr before sensitization. The treated animals did not respond to a second sensitization/challenge, showing that tolerance had been induced. MECHANISM OF ACTION : (I) inhibits activation of the NF-kappaB transcription factor by cytokines or lipopolysaccharide; Reduces expression of costimulatory molecules from dendritic cells and increases production of interleukin-10 from monocytes. (I) may bind to the beta -adrenergic and type 1 interleukin-1 receptors, possibly also to other receptors.