the 144 , 000 are Jews that have been saved
jh: watchtower writers operate under the assumption that all references to "jew" Israelite, has changed for Christians with Paul's introduction in Gal 6:16 of the 'Israel of God" aka "spiritual Israel", made up of spiritual jews.
All Israel was in the law covenant, all spiritual jews are in the new covenant, all must take the emblems of that covenant for forgiveness of sin.
Particularly the so called OS, because unlike the "anointed" , who die to go to heaven, the supposed future survivors of Armageddon would never personally pay the penalty for sin.
Christ died for the world. the world's believers, , not only the 144000 should partake.
no text says otherwise.