fendant's immunized testi- mony had helped lead to the indictment on the gun charge. See also United States Gallo, 859 F.24 1078, 1088 (24 Cir.19 (Van Crasfeiland, J., concurring) ("Licens- ing and taxing statutes aside, the only haz- ards of incrimination that are likely to be considered substantial and real