Induction of persistent autoimmune haemolytic anaemia in mice by combined use of rat erythrocyte preimmunization and chronic GVHR.

Female F1 mice (BDF1: C57BL/6 x DBA/2, BCF1: C57BL/6 x C3H/HeN, BBF1: C57BL/6 x BALB/c) were preimmunized with rat erythrocytes and then received splenic T cells from parental female C57BL/6 mice injected with hydrocortisone acetate before killing. In BDF1 and BCF1 mice, direct Coombs' test (DCT) positivity persisted for more than 4 months in almost all mice. They also showed haematological sign of anaemia, and the survival of infused 51Cr-labelled parental C57BL/6 erythrocytes was reduced. In BBF1 mice, DCT positivity returned to negative within 2 months. Autoantibodies were eluted from DCT-positive erythrocytes and their specificities were examined. They were capable of binding equally well to erythrocytes from all strains of mice tested, including the donor mice. They also cross-reacted with rat erythrocytes but not with sheep, rabbit or human erythrocytes. Isotypes of the autoantibodies eluted were also examined. Interestingly, isotypes of the autoantibodies obtained from individual mice were confined to one or other subclass of IgG isotype: IgG1, IgG2a or IgG2b.