The TeX Catalogue OnLine, Entry for isf, Ctan Edition

Access italic computer modern sans in LaTeX 2.09

Provides LaTeX 2.09 (dynamic-loading) font tables for a font selection command \isf, giving access to Computer Modern Sans Serif ‘Italic’ fonts. (The font is actually a slanted version.)

Note that these macros do not work with current LaTeX, but since the NFSS supports the fonts anyway, this is not a problem.