disclosed is the novel use of some aza - podophyllotoxin derivatives for modulation of the immune system , including a method for modulating an immune response comprising administering to a subject an effective amount of at least one aza - podophyllotoxin derivative of general formula wherein a - ring is selected from the group consisting of 1 , 3 - dioxolane , cyclopentane , 1 , 4 - dioxane , one methoxy , two methoxys , and ethyl ; and wherein e - ring is selected from the group consisting of dimethoxyanisole , veratrol , anisole , benzene , syringol , bromobenzene , chlorobenzene , 1 , 2 - dichlorobenzene , 2 , 3 - dimethoxybenzene , 3 , 4 , 5 - trimethoxybenzene .