  Discrete symmetries are studied in warped space-times with one extra
dimension. In particular, we analyze the compatibility of five- and
four-dimensional charge conjugation, parity, time reversal and the orbifold
symmetry Z_2 with localization of fermions on the four-dimensional brane-world
and Lorentz invariance. We then show that, when a suitable topological scalar
field (the ``kink'') is included, fermion localization is a consequence of
(five-dimensional) CPT invariance.
