Abstract: The present invention relates to a method for preparing an antibody selective for activating antibody Fc region receptors (FcRs) comprising an ITAM motif or motifs (immunoreceptor tyrosine-based activation motif), comprising the steps of obtaining monoclonal antibodies from a hybridoma, from a heterohybridoma or from any animal, plant or human cell line, replacing each of the His 310 and His 435 residues (Cabat numbering) of the Fc region of said antibody with a residue chosen from lysine, alanine, glycine, valine, leucine, isoleucine, proline, methionine, tryptophan, phenylalanine, serine or threonine, and then selecting the antibodies for which the binding to inhibitory FcRs comprising ITIM motifs (immunoreceptor tyrosine-based inhibition motif) is decreased by at least 30%, preferably by at least 50%, 70%, 80% or else by at least 90% relative to the same antibody having a natural Fc region.