Lack of surface TNFR1 in T50M “knock-in” mice. (A) Peripheral-blood neutrophils (GR1⁺CD11b⁺) from mice with the indicated genotypes were stained with biotinylated anti-TFNR1 and streptavidin-PE before (surface) or after (intracellular) permeablization. Staining with isotype control biotinylated hamster Ig was equivalent to TNFR1 KO (data not shown). (B) Immunoprecipitation of wild-type and T50M equivalent mutant TNFR1. Splenocytes from mice of the indicated genotypes were lysed and immunoprecipitated with hamster anti–mouse TNFR1, followed by reducing SDS-PAGE and immunoblotting with rabbit anti-TNFR1.