Isolation of a peptide associated with autoimmune haemolytic anaemia from red cell membranes.

A 12,000 molecular weight (12 kD) peptide which did not relate to immunoglobulins or complements was purified from the supernatants of dispase-treated red cells of four patients with autoimmune haemolytic anaemia (AIHA). The isoelectric point (pI) was about 5.3. This peptide was not obtained from normal persons and patients with other haemolytic anaemias. The peptide and the red cell autoantibody disappeared in a patient with angio-immunoblastic lymphadenopathy with dysproteinaemia (AILD) after intensive chemotherapy. The result indicates an abnormality in the composition of red cell membrane proteins in AIHA.