Induction of promotive rather than suppressive immune responses from a novel NKT cell repertoire Valpha19 NKT cell with alpha-mannosyl ceramide analogues consisting of the immunosuppressant ISP-I as the sphingosine unit.

A 2-substituted 2-aminopropane-1,3-diol or 2-aminoethanol is the minimum structure required for the immunosuppressive activity of ISP-I, an antibiotic isolated from the culture broth of Isaria sinclairil. A series of alpha-mannosyl ceramide (alpha-ManCer) analogues was derived from 2-substituted 2-aminopropane-1,3-diols or 2-aminoethanols in place of sphingosine. The newly synthesized glycosides were evaluated for their effects on immune responses. In contrast to the immunosuppressive activity of the precursors, the alpha-ManCer analogues induced immunopromotive responses from invariant Valpha19-Jalpha26 transgenic mouse lymphocytes more effectively than the original alpha-ManCer. Collectively, it is strongly suggested that the 2-substituted 2-aminopropane-1,3-diols and 2-aminoethanols mimic sphingosine in the alpha-ManCer analogues so that they potentially acquire specific antigenicity toward Valpha19 NKT cell, a novel NKT cell subset.