Abstract: A biologically active substance comprising a kind of glycolipid having an elemental analysis (%) of H: 5.20-5.40, C: 42.55-44.17 and N: 3.94-4.08 and a molecular weight of about 30,000-10.sup.6 is obtained by extracting the tissue of a plant of maize (Zea mays Linne) or a variant thereof by extracting the tissue with water and recovering the desired active substance from the resultant extract. This substance is capable of inhibiting the formation of IgE antibodies and promoting the formation of IgG and IgM antibodies, and moreover exhibits various biological activities such as interferon-inducing activity, polyclonal B lymphocite activating activity, mitrogenic activity, adjuvant activity and anti-tumour activity. Thus, this substance is expected to be useful for preventing and treating, for example, aesthema, rhintitis, B-type hepatitis, AIDS and other allergic diseases and immunological insufficiency.