The present invention relates to selectively controlling the function of ahelperT cell. In the present invention, a mouse lacking a gene involved ingangliosidebiosynthesis (ganglioside GM3 synthetase gene) (SAT-1 KO) was produced andanalyzed. As a result, the present invention provides, for example, a methodforscreening a substance which induces selective suppression of the function of ahelper Tcell in an immune response, including control of production of asphingoglycolipid inthe helper T cell, and moderation or suppression of an excessive immuneresponsecaused by the suppression of the function, that is, a substance having animmunosuppression activity, an anti-asthmatic action and/or an anti-allergicaction.
