To determine the mechanism underlying the immune response after allograft (mantle grafts of Pinctada fucata) and xenograft (mantle pieces of Pinctada maxima) transplantations in the pearl oyster Pinctada fucata, two sets of serum were obtained at different times (6, 12, 24, 48, 96, 144 and 192 h) after allograft and xenograft transplantations and proteomic responses were evaluated by using isobaric tags for relative and absolute quantification labeling coupled with liquid chromatography (LC) / tandem mass spectrometric (MS) analysis.