The present invention relates to an immunosuppressing method which comprises administering a spergualin-related compound represented by the following formula <IMAGE> +TR NH(CH2)3NH (wherein R1 is -(CH2)4-, -(CH2)6-, <IMAGE> +TR <IMAGE> R2 is -(CH2)2- or -CH=CH-; and R3 is <IMAGE> or pharmacologically acceptable salts thereof in an effective amount to a warm-blood animal.
