Hi Ron-- I don't believe that antialiased lines were supported that far back. AFAICT, cartographic symbols supporting antialiased lines and much more were introduced in 4.6 (see http://mapserver.gis.umn.edu/docs/howto/cartosymbols/), while a more straightforward approach to antialiased lines was introduced in 4.8 (see http://mapserver.gis.umn.edu/docs/faq/antialiasedlines).
HTH, --Ken
