The present disclosure provides anti-amyloid β (Aβ) antibodies and antibody fragments that preferentially bind soluble amyloid Aβ protofibril/oligomer and trigger ADPC in microglial cells, anti-amyloid β (Aβ) antibodies and antibody fragments that reduce soluble amyloid Aβ protofibril/oligomer levels and insoluble amyloid Aβ plaque in brain tissue, and the use of anti-Aβ protofibril/oligomer antibodies and antibody fragments in therapy, prophylaxis, diagnosis, screening, and monitoring of conditions associated with Aβ protein aggregation, in particular Alzheimer's disease (AD).