THE PRESENT INVENTION RELATES TO A MONOCLONAL ANTIBODY WHICH SPECIFICALLY BINDS TO THE N-TERMINAL REGION OF Aβ8-X PEPTIDE, X BEING COMPRISED FROM 11 TO 42, AND RECOGNISES NEITHER Aβ1-40 NOR Aβ1-42 AND WHICH PRESENTS A HIGH AFFINITY WITH RESPECT TO Aβ8-X PEPTIDE, SUCH AS DETERMINED BY AN IMMUNOLOGICAL COMPLEX FORMATION BETWEEN THE MONOCLONAL ANTIBODY AND THE PEPTIDE Aβ8-X.