The present invention relates in essence to a method for detecting a subset of cells with a binding domain which is specific for a target which characterizes said subset of cells, which method comprises detecting, ex vivo, said subset of cells, wherein said binding domain is to be administered to a subject which comprises or is assumed to comprise said subset of cells, prior to the removal of said subset of cells. The present invention also relates to the use of a binding domain as defined herein in a method defined herein. The use of a binding domain as defined herein for the preparation of a diagnostic composition to be used in a method defined herein is also envisaged. In another aspect, the present invention relates to the binding domain as defined herein to be used in a method defined herein. Kits comprising a binding domain as defined herein and means to administer said binding domain to a subject, and, optionally, means to detect said binding domain with a method defined herein, are also disclosed. In another aspect, the present invention relates to the use of a binding domain, preferably a therapeutically effective antibody like for example alemtuzumab, apolizumab, cetuximab, epratuzumab, galiximab, gemtuzumab, ipilimumab, labetuzumab, panitumumab, rituximab, trastuzumab, nimotuzumab, mapatumumab, matuzumab, rhMab ICR62, rhMab B-Ly1 and pertuzumab etc including combinations thereof, for the preparation of a pharmaceutical composition for the treatment of patients disposed to respond favorably to said binding domain as identified by a method defined herein.La présente invention concerne essentiellement un procédé de détection dun sous-ensemble de cellules dans un domaine de liaison qui est spécifique à une cible qui caractérise ledit sous-ensemble de cellules, ledit procédé comprenant la détection, ex vivo, dudit sous-ensemble de cellules. Selon linvention, ledit domaine de liaison est administré à un sujet qui comprend ou est supposé comprendre ledit sous-en
