Synonyms for Immune (same or very similar meaning)
WordNet sense 1 ((of persons) freed from or not subject to an obligation or liability (as e.g. taxes) to which others or other things are subject):
exemptWordNet sense 2 (relating to or conferring immunity (to disease or infection)):
resistantWordNet sense 3 (undergoing no change when acted upon):
unaffectedFrom the ODE community, based on WordNetadd/edit