All dogs should be crossmatched after a second blood transfusion. Neonates that inherit the blood group of the sire develop hemolytic anemia when they ingest colostrum containing antibodies against their and the sire's erythrocytes. This has been reported in cats, dogs, cows, pigs and horses. In cats, it occurs with type B queens mated to A or AB toms. In this situation, all kittens bearing the type A antigen will suffer a hemolytic anemia at birth after ingestion of colostrum containing naturally occurring anti-type A antibodies.
Affected kittens can also suffer from tail tip necrosis.
Neonatal immune-mediated thrombocytopenia has also been reported. This is mediated by IgE antibodies which activate mast cells, which then release inflammatory and vasoactive mediators, that produce hypotension, increased vascular permeability, bronchiolar constriction, urticaria and pruritis. The exact mechanism of this reaction is uncertain, but it is likely due to cytokines or other products which activate the same inflammatory and vasoactive mediators. Allergens in the donor blood include antibiotics or chemicals used in blood preparation, albumin and C4. Rarely, transfused IgE antibodies from the donor can initiate the reaction.