Characterisation of autoantibodies to erythrocytes in autoimmune haemolytic anaemia by chloroquine.

Chloroquine splits autoantibodies from erythrocytes of patients with autoimmune haemolytic anaemia in vitro. After the removal of chloroquine from the samples the autoantibodies can be identified in the eluates. With one exception the autoantibodies of patients with idiopathic autoimmune haemolytic anaemia (AIHA) and severe haemolysis were completely split from the cells, whereas the autoantibodies of patients with symptomatic AIHA and moderate anaemia, of patients with diseases unrelated to haemolysis, and of healthy persons, were not completely split from the erythrocytes. In general, autoantibodies, which are associated with severe haemolysis, were more easily split from the red cells by chloroquine. The eluted IgG incomplete warm autoantibodies were only in part specific to Rh antigens. The Rh specificity does not correlate with the absence of presence of increased haemolysis. The inhibition of the autoantibodies and the splitting or 'loosening' of the antigen-antibody linkage with the immunocomplex by chloroquine could be responsible of a longer survival of autoantibody-coated red cells in patients with AIHA.