  There are gauge-transformation operators applicable to massless spin-1/2
particles within the little-group framework of internal space-time symmetries
of massive and massless particles. It is shown that two of the $SL(2,c)$
spinors are invariant under gauge transformations while the remaining two are
not. The Dirac equation contains only the gauge-invariant spinors leading to
polarized neutrinos. It is shown that the gauge-dependent $SL(2,c)$ spinor is
the origin of the gauge dependence of electromagnetic four-potentials. It is
noted also that, for spin-1/2 particles, the symmetry group for massless
particles is an infinite-momentum/zero-mass limit of the symmetry group for
massive particles.
