The quark loop contribution to the Reggeon-Reggeon-gluon vertex is cal
culated in QCD, where the Reggeon is the Reggeized gluon. Compared wit
h the vertex in the Born approximation, this contribution exhibits a n
ew spin structure as well as the gluon loop one. A remarkable but not
complete cancellation between gluon and quark contributions to this ne
w spin structure takes place for the case of three massless quark flav
ors.